STORAGE INDUCED CHANGES IN THE PHYSICOCHEMICAL AND SENSORIAL PROPERTIES OF
NATURAL ORANGE JUICE AND DRINK
By
Razan Elbukhari Ibrahim
B.Sc. (Agric.)
University of Khartoum
December 2003
A thesis submitted to the University of Khartoum in partial
fulfillment of the requirements for the degree of M.Sc. (Agric.)
Supervisor:
Prof. Elgasim Ali Elgasim
Department of Food Science and Technology
Faculty of Agriculture,
University of Khartoum
May 2007
DEDICATION
To my supervisor
To my beloved family & husband
For patience & unlimited support.
To my friends and colleagues
I
ACKNOWLEDGMENTS
Foremost, I owe sincere gratitude and praise to Allah Alazeem
who gave me the power and durable patience to finish this study.
I would like to express my deepest respect and thanks to my
supervisor Prof. Elgasim Ali Elgasim, for his great assistance,
valuable advice, kind supervision and unremitting suggestions
through out my master program.
Special thanks to Mr. Mohammed Saeed, in national chemical
laboratories.
Deep thanks to my teachers, colleagues, friends and all those who
offered me their valuable knowledge and trust.
II
ABSTRACT
A completely randomized design was used to study the effects of
temperature and the storage period on the natural orange drink from a local
processing company in Khartoum state and orange juice processed at home
from local orange fruits and stored for three days at refrigeration temp. and
room temp. while the commercial drink was stored for twelve weeks at the
same temperature conditions in the market. Samples are analyzed for
proximate composition (moisture content, fiber, protein, carbohydrate, oil
and ash), pH value, titratable acidity, total soluble solids, ascorbic acid,
minerals (potassium, sodium, calcium, magnesium) and sensory evaluation.
The results indicated significant (P≤ 0.05) changes at the end of storage
period for the orange juice and orange drink samples especially pH values,
acidity, total soluble solids and ascorbic acid. The pH value and acidity of
the two samples decreased and increased, respectively with the increasing
of storage period. The total soluble solids for natural orange drink samples
stored at the two temperature conditions increased. On the other hand the
total soluble solids of orange juice samples decreased and increased for the
refrigerated and room temperature samples, respectively for the same
storage period. A significant decrease in ascorbic acid was observed with the
increase in the storage period for the two samples, where the natural orange
sample lost more than 50% of their original value at the end of storage
period (twelve weeks). The home made orange juice lost 28.5% at the end of
storage period (three days). A decrease in minerals content was observed for
the natural orange drink at the end of storage (twelve weeks). Orange juice
did not show significant (p≥0.05) changes in the minerals content under the
storage conditions investigated.
III
‫ﻤﻠﺨﺹ ﺍﻷﻁﺭﻭﺤﻪ‬
‫ﺃﺠﺭﻴﺕ ﺘﺠﺭﺒﻪ ﻓﻲ ﺘﺼﻤﻴﻡ ﺘﺎﻡ ﺍﻟﻌﺸﻭﺍﺌﻴﺔ ﻟﺩﺭﺍﺴﺔ ﺘﺄﺜﻴﺭ ﺩﺭﺠﺔ ﺍﻟﺤﺭﺍﺭﺓ ﻭﻓﺘﺭﺓ ﺍﻟﺘﺨﺯﻴﻥ ﻋﻠـﻲ‬
‫ﺸﺭﺍﺏ ﻋﺼﻴﺭ ﺍﻟﺒﺭﺘﻘﺎل ﺍﻟﻁﺒﻴﻌﻲ ﺍﻟﻤﺼﻨﻊ ﻓﻲ ﺍﺤﺩ ﻤﺼﺎﻨﻊ ﻭﻻﻴﺔ ﺍﻟﺨﺭﻁﻭﻡ‪ ،‬ﻭﻋﺼﻴﺭ ﺒﺭﺘﻘﺎل‬
‫ﻁﺎﺯﺝ ﻤﺼﻨﻊ ﻤﻨﺯﻟﻴﺎ ﻤﻥ ﻓﺎﻜﻬﺔ ﻤﺤﻠﻴﺔ ﻭﺘﻡ ﺘﺨﺯﻴﻨﻪ ﻟﻤﺩﺓ ﺜﻼﺜﺔ ﺃﻴﺎﻡ ﻓﻲ ﺩﺭﺠﺔ ﺤﺭﺍﺭﺓ ﺍﻟﻐﺭﻓﺔ‬
‫ﻭ ﺩﺭﺠﺔ ﺤﺭﺍﺭﺓ ﺍﻟﺜﻼﺠﺔ ﺒﻴﻨﻤﺎ ﺨﺯﻥ ﺍﻟﻤﺸﺭﻭﺏ ﺍﻟﺘﺠﺎﺭﻱ ﻟﻤﺩﺓ ﺃﺜﻨﺎ ﻋﺸﺭ ﺃﺴﺒﻭﻋﺎ ﻓـﻲ ﻨﻔـﺱ‬
‫ﺩﺭﺠﺘﻲ ﺍﻟﺤﺭﺍﺭﺓ ﻓﻲ ﺍﻟﺴﻭﻕ )ﺴﻭﺒﺭ ﻤﺎﺭﻜﺕ(‪ .‬ﻭﺘﻡ ﻗﻴﺎﺱ ﺍﻟﺘﺤﻠﻴل ﺍﻟﺘﻘﺭﻴﺒﻲ ) ﺭﻁﻭﺒﺔ‪ ،‬ﺃﻟﻴﺎﻑ‪،‬‬
‫ﺒﺭﻭﺘﻴﻥ‪ ،‬ﻜﺎﺭﺒﻭﻫﻴﺩﺭﺍﺕ‪ ،‬ﺯﻴﺕ‪ ،‬ﺭﻤﺎﺩ(‪ ،‬ﺍﻷﺱ ﺍﻟﻬﻴﺩﺭﻭﺠﻴﻨﻲ‪ ،‬ﺩﺭﺠﺔ ﺍﻟﺤﻤﻭﻀﺔ‪ ،‬ﺍﻟﻤﻭﺍﺩ ﺍﻟﺫﺍﺌﺒﺔ‬
‫ﺍﻟﺼﻠﺒﺔ‪ ،‬ﻓﻴﺘﺎﻤﻴﻥ ﺝ‪ ،‬ﺍﻟﻤﻌﺎﺩﻥ )ﺍﻟﺒﻭﺘﺎﺴﻴﻭﻡ‪ ،‬ﺍﻟﺼﻭﺩﻴﻭﻡ‪ ،‬ﺍﻟﻜﺎﻟﺴﻴﻭﻡ‪ ،‬ﺍﻟﻤﺎﻏﻨﻴـﺴﻴﻭﻡ( ﻭﺍﻟﺘﻘﻴـﻴﻡ‬
‫ﺍﻟﺤﺴﻲ ) ﺍﻟﻠﻭﻥ‪ ،‬ﺍﻟﺭﺍﺌﺤﺔ‪ ،‬ﺍﻟﻁﻌﻡ‪ ،‬ﺩﺭﺠﺔ ﺍﻟﻘﺒﻭل(‪ .‬ﻭﺃﻅﻬﺭﺕ ﺍﻟﻨﺘﺎﺌﺞ ﻓﺭﻭﻕ ﻭﺍﻀـﺤﺔ ﻓـﻲ‬
‫ﺍﻟﻘﻴﻡ ﻓﻲ ﻨﻬﺎﻴﺔ ﻓﺘﺭﺓ ﺍﻟﺘﺨﺯﻴﻥ ﻟﻠﻌﻴﻨﺘﻴﻥ ﻭﺨﺼﻭﺼﺎ ﻋﻠﻲ ﻗﻴﻡ ﺍﻷﺱ ﺍﻟﻬﻴـﺩﺭﻭﺠﻴﻨﻲ‪ ،‬ﻭﺩﺭﺠـﺔ‬
‫ﺍﻟﺤﻤﻭﻀﺔ‪ ،‬ﻭﺍﻟﻤﻭﺍﺩ ﺍﻟﺫﺍﺌﺒﺔ ﺍﻟﺼﻠﺒﺔ ﻭ ﻓﻴﺘـﺎﻤﻴﻥ ﺝ‪ .‬ﺤﻴـﺙ ﻟـﻭﺤﻅ ﺍﻨﺨﻔـﺎﺽ ﻓـﻲ ﺍﻷﺱ‬
‫ﺍﻟﻬﻴﺩﺭﻭﺠﻴﻨﻲ ﻴﻘﺎﺒﻠﻪ ﺍﺭﺘﻔﺎﻉ ﻓﻲ ﺩﺭﺠﺔ ﺍﻟﺤﻤﻭﻀﺔ ﻓﻲ ﺍﻟﻌﻴﻨﺘﻴﻥ ﻜﻤﺎ ﻟﻭﺤﻅ ﺍﺭﺘﻔﺎﻉ ﻓـﻲ ﻨـﺴﺒﺔ‬
‫ﺍﻟﻤﻭﺍﺩ ﺍﻟﺫﺍﺌﺒﺔ ﺍﻟﺼﻠﺒﺔ ﻓﻲ ﻋﻴﻨﺔ ﺍﻟﻌﺼﻴﺭ ﺍﻟﺘﺠﺎﺭﻱ ﻓﻲ ﺠﻤﻴﻊ ﻅﺭﻭﻑ ﺍﻟﺘﺨـﺯﻴﻥ ﺃﻤـﺎ ﻋﻴﻨـﺔ‬
‫ﺍﻟﻌﺼﻴﺭ ﺍﻟﻁﺎﺯﺝ ﻓﻘﺩ ﺴﺠﻠﺕ ﺍﻨﺨﻔﺎﺽ ﻟﻠﻤﻭﺍﺩ ﺍﻟﺫﺍﺌﺒﺔ ﺍﻟﺼﻠﺒﺔ ﻓﻲ ﺍﻟﻌﻴﻨﺔ ﺍﻟﻤﺨﺯﻨﺔ ﻓﻲ ﺩﺭﺠـﺔ‬
‫ﺤﺭﺍﺭﺓ ﺍﻟﻐﺭﻓﺔ ﻭﺍﺭﺘﻔﺎﻉ ﻏﻴﺭ ﻤﻌﻨﻭﻱ ﻓﻲ ﻨﺴﺒﺔ ﺍﻟﻤﻭﺍﺩ ﺍﻟﺫﺍﺌﺒﺔ ﺍﻟﺼﻠﺒﺔ ﻓـﻲ ﺩﺭﺠـﺔ ﺤـﺭﺍﺭﺓ‬
‫ﺍﻟﺜﻼﺠﺔ ﻟﻨﻔﺱ ﻓﺘﺭﺓ ﺍﻟﺘﺨﺯﻴﻥ‪ .‬ﻭﺃﻴﻀﺎ ﻓﻴﺘﺎﻤﻴﻥ ﺝ ﺴﺠل ﺍﻨﺨﻔﺎﺽ ﻜﺒﻴﺭ ﻋﻠـﻲ ﻁـﻭل ﻓﺘـﺭﺓ‬
‫ﺍﻟﺘﺨﺯﻴﻥ ﻓﻲ ﻜﻼ ﺍﻟﻌﻴﻨﺘﻴﻥ ﻓﻨﺠﺩ ﺃﻥ ﻋﻴﻨﺔ ﺸﺭﺍﺏ ﺍﻟﺒﺭﺘﻘﺎل ﻗﺩ ﻓﻘﺩﺕ ﺃﻜﺜﺭ ﻤﻥ ‪ %50‬ﺘﻘﺭﻴﺒﺎ ﻤﻥ‬
‫ﻤﺤﺘﻭﺍﻫﺎ ﻟﻔﻴﺘﺎﻤﻴﻥ ﺝ ﺒﻨﻬﺎﻴﺔ ﻓﺘﺭﺓ ﺍﻟﺘﺨﺯﻴﻥ )ﺍﺜﻨﺎ ﻋﺸﺭ ﺃﺴﺒﻭﻋﺎ( ﺒﻴﻨﻤﺎ ﻓـﻲ ﻋﻴﻨـﺔ ﺍﻟﻌـﺼﻴﺭ‬
‫ﺍﻟﻁﺒﻴﻌﻲ ﺍﻟﻤﺼﻨﻊ ﻤﻨﺯﻟﻴﺎ ﻜﺎﻥ ﺍﻟﻔﻘﺩ ﻓﻲ ﺤﺩﻭﺩ ‪ %28.5‬ﺒﻨﻬﺎﻴﺔ ﻓﺘﺭﺓ ﺍﻟﺘﺨﺯﻴﻥ )ﺜﻼﺜـﺔ ﺃﻴـﺎﻡ(‪.‬‬
‫ﺴﺠﻠﺕ ﺍﻟﻤﻌﺎﺩﻥ ﺃﻴﻀﺎ ﺍﻨﺨﻔﺎﻀﺎ ﺒﻨﻬﺎﻴﺔ ﻓﺘﺭﺓ ﺍﻟﺘﺨﺯﻴﻥ ﻓﻲ ﻋﻴﻨﺔ ﺸﺭﺍﺏ ﺍﻟﺒﺭﺘﻘﺎل‪ .‬ﺃﻤـﺎ ﻋﻴﻨـﺔ‬
‫ﻋﺼﻴﺭ ﺍﻟﺒﺭﺘﻘﺎل ﻟﻡ ﻴﺤﺩﺙ ﺒﻬﺎ ﺘﻐﻴﻴﺭ ﻟﻘﻴﻤﺘﻬﺎ ﻤﻥ ﺍﻟﻤﻌﺎﺩﻥ ﺤﺘﻰ ﻨﻬﺎﻴﺔ ﻓﺘﺭﺓ ﺍﻟﺘﺨـﺯﻴﻥ )ﺜﻼﺜـﺔ‬
‫ﺃﻴﺎﻡ(‪ .‬ﻜﻤﺎ ﻟﻭﺤﻅ ﺃﻥ ﺩﺭﺠﺔ ﺍﻟﺘﺩﻫﻭﺭ ﻓﻲ ﺠﻤﻴﻊ ﺍﻟﻘﻴﻡ ﻜﺎﻥ ﺍﻜﺒﺭ ﻓﻲ ﺍﻟﻌﻴﻨـﺎﺕ ﺍﻟﻤﺨﺯﻨـﺔ ﻓـﻲ‬
‫ﺩﺭﺠﺔ ﺤﺭﺍﺭﺓ ﺍﻟﻐﺭﻓﺔ‪ ،‬ﻭﻫﺫﺍ ﻴﻭﻀﺢ ﺃﻥ ﻟﺩﺭﺠﺔ ﺍﻟﺤﺭﺍﺭﺓ ﺩﻭﺭ ﻜﺒﻴﺭ ﻓﻲ ﺘﺩﻫﻭﺭ ﺍﻟﻘﻴﻤﺔ ﺍﻟﻐﺫﺍﺌﻴﺔ‬
‫ﻟﻠﻌﺼﺎﺌﺭ‪.‬‬
‫‪IV‬‬
TABLE OF CONTENTS
Title
Page No.
I
Dedication
Acknowledgment
English abstract
Arabic abstract
Table of Contents
List of tables
List of figures
1. INTRODUCTION
II
III
IV
V
VII
VIII
1
2. LITERATURE REVIEW
2.1. History of citrus
2.2. Uses of citrus
2.3. Characteristics of citrus juices
2.4. Composition and nutritive value of fruit juices
2.4.1. Acidity and pH
2.4.2. The total soluble solids (Brix)
2.4.3. Minerals
2.4.4. Vitamins
2.5. Effect of storage on the nutritive value of juices
2.5.1. Non-enzymatic browning
2.6. Orange juice
2.6.1. Types of orange juices
2.6.1.1. Fresh squeezed orange juice
2.6.1.2. Frozen concentrated orange juice
2.6.1.3. Not-from-concentrate orange juice
2.6.1.4. Refrigerated orange juice from concentrate
2.6.2. Orange Juice processing
2.6.3. Quality control
2.6.4. Microbiology of orange juice
2.6.5. Nutritional and health benefits of orange fruit and juice
2.7. Consumption of fruits and fruit juices in Sudan
4
4
5
6
6
8
8
9
10
12
14
15
16
16
16
17
17
18
21
21
22
23
3. MATERIALS AND METHODS
3.1. Materials
3.2. Methods
3.2.1. Proximate composition
3.2.2. pH value
3.2.3. Titratable acidity
25
25
26
26
29
30
V
3.2.4. Total soluble solids (T.S.S.)
3.2.5. Ascorbic acid
3.2.6. Minerals
3.2.7. Sensory evaluation
3.2.8. Statistical analysis
30
30
31
33
33
4. RESULTS AND DISSCUTION
4.1. orange drink
4.1.1. Proximate composition
4.1.2. pH value
4.1.3. Titratable acidity
4.1.4. Total soluble solids (TSS)
4.1.5. Ascorbic acid
4.1.6. Minerals
4.1.7. Sensory evaluation
4.2. Fresh orange juice
4.2.1. Proximate composition
4.2.2. pH value
4.2.3. Titratable acidity
4.2.4. Total soluble solids (TSS)
4.2.5. Ascorbic acid
4.2.6. Minerals
4.2.7. Sensory evaluation
Conclusion
Recommendations
34
34
34
38
38
42
42
46
48
52
52
52
54
54
54
56
56
60
60
References
61
VI
LIST OF TABLES
Table
Page No.
Table [1]: The effect of refrigerated storage on the proximate
composition of orange drink.
35
Table [2]: The effect of room temperature storage on the
proximate composition of orange drink.
37
Table [3]: The effect of refrigerated storage on the Minerals
(K - Na – Ca – Mg) of orange drink.
49
Table [4]: The effect of room temperature storage on the Minerals
(K -Na– Ca– Mg) of orange drink.
50
Table [5]: The effect of storage period and temperature on the
sensory evaluation of orange drink stored
for 12 weeks.
51
Table [6]: The effect of storage period at refrigeration temp. on the
proximate composition of fresh orange juice.
53
Table [7]: The effect of storage period at room temp. on the
proximate composition of fresh orange juice.
53
Table [8]: The effect of storage period at refrigeration temp. on the
pH, acidity, TSS, ascorbic acid of fresh orange juice.
55
Table [9]: The effect of storage period at room temp. on the
pH, acidity, TSS, ascorbic acid of fresh orange juice.
55
Table [10]: The effect of storage period at refrigeration temp. on the
minerals (K- Na - Ca - Mg) of fresh orange juice.
57
Table [11]: The effect of storage period at room temp. on the
minerals (K - Na - Ca - Mg) of fresh orange juice.
57
Table [12]: The effect of storage period and temperature on sensory
evaluation of fresh orange juice stored for 3 days
59
VII
LIST OF FIGURES
Figure
Page No.
Figure (1): The effect of storage period and temperature on
40
the pH value of natural orange drink.
Figure (2): The effect of storage period and temperature on
41
the titratable acidity of natural orange drink.
Figure (3): The effect of storage period and temperature on the
44
total soluble solids of natural orange drink.
Figure (4): The effect of storage period and temperature on the
ascorbic acid of natural orange drink.
VIII
45
Chapter One
INTRODUCTION
Fruit juices are good sources of vitamins particularly vit-C and minerals.
They are recognized as contributing to the five portions per day of fruit
and vegetables currently recommended.
Some fruit juice has been made from fruit juice concentrate. This
concentrate comes from fresh fruit, but the water content is reduced to
make storage and transport easier. They use brix and acid ratios to ensure
that it meets the internationally recognized standards. Fruit juices may be
defined as the liquid expelled by pressure of other mechanical means from
the edible portion of the fruit. It will be containing cellular components in
colloidal suspension with variable amounts of finely divided tissue. It may
also contain oily or waxy material and carotenoid pigments derived from
the skin of rind of the fruit (Hulme, 1971). Often described as ‘direct’ or
‘not from concentrate’. Fruit juice drinks contain fruit juice, but are not
made exclusively from fruit juice. They are products that may contain a
high proportion of water and have other ingredients like sugar, flavours,
food additives, preservatives and extra vitamins added.
The Sudan market for commercially packaged juice products was small
due to the fact that consumers are used to fresh fruit juices from fruits
grown locally which they squeeze fresh at home. Nowadays there are
many packaged juices drinks (commercially packaged juice products).
Fruit juices are widely consumed in ever-increasing quantities and are
very important in the trade of most countries .The Institute for Monetary
and Economic Studies (IMES, UK) performed a research report on the
Sudan market consumption of ready to drink juice products, and reported
1
that the consumption increased from 0.2 million liter in the year 1995 to
1.3 million liter in the year 2000, and consumption grow at a rate of 12%
through the following five years that maybe due to the income increasing;
increased nutritional wariness; changes in food habits; increased fast food
outlets. In comparison with the neighboring countries if we look to the
Saudi Arabia market we fined that the IMES consultancy limited reported
that consumption of fruit juice and drinks in 1992-1996 increased from
236 million liters in the year 1992 to 321 million liters in the year 1996
and increased to reach 392 million liters in the year 2000.
Many consumers consider orange juice the best source of vitamin C in
their diets. Although several foods are richer in vitamin C than citrus
fruits, orange juice is the most popular. Whitney and Rolfes, (1999)
reported that 225 ml of orange juice contains approximately 125 mg of
vitamin C. United States National Academy of Sciences, Food and
Nutrition Board, (1990) reported that the recommended daily allowance of
vitamin C is 30 to 100 mg/day for most people.
Juice under go changing on storage due to chemical reactions between
their constituents (Hulme, 1970). The loss of nutritional quality during the
processing and storage of beverage has become an increasingly important
problem with the introduction of nutrition labeling regulations. The loss of
some nutrients, including ascorbic acid, may actually become the limiting
factor in determining the shelf-life of some products (Laing et al., 1978).
Over recent years the fruit juice market has become sub-divided into
three main types, Long Life, Short Life Chilled and Unpasteurized or
‘Freshly Pressed’ Juices. Long life and short life products are pasteurized
to varying degrees which then has a direct effect on their shelf life. For
example long life juices usually keep for 6 to 9 months while the
2
packaging is kept sealed, and because of the pasteurization process
applied and packing method, do not require chilling. Short life products
have a shelf life of 2 to 6 weeks and do sometimes require chilling.
Unpasteurized juices are obtained from freshly pressed fruit and are
usually packed and delivered to retailers within 24 hours. Therefore the
freshly pressed juice must be kept chilled and has a very limited life of
only few days.
There are many studies for determining the ascorbic acid content in fruit
juices but only a few aiming at determining the amounts of ascorbic acid
lost from different fruit juices under different storage conditions. This fact
is of great importance to the consumer who must know how to store the
juice containers and when to consume them in order to get the maximum
benefit of their vitamin C content.
In Sudan, studies on orange juices are very limited and the industry of
fruit juices in general and orange juices in particular is still under
developing. The Sudanese orange drinks are made mainly from imported
orange juice concentrate and most of the orange juices are found in
packages.
The current study aimed to determine the effect of storage temperature
and period on the physico-chemical and sensorial properties of pasteurized
orange drink and unpasturized orange juice. To measure the amount of
ascorbic acid lost under different storage conditions, namely, closed
containers, storage in the refrigerator and at room temperature.
3
Chapter two
LITERATURE REVIEW
2.1. History of citrus
Citrus fruits (Citrus
Species), from the family Rutaceae, consist of
seven subfamilies with 148 genera. It is native to tropical and subtropical
regions of Asia and Malaya (Mahadi, 1979).
Citrus fruits are produced all over the world. According to FAO data, in
2004, 140 countries produced citrus fruits. However, most production is
concentrated in certain areas. Most citrus fruits are grown in the Northern
Hemisphere, accounting for around 70% of total citrus production. Main
citrus fruit producing countries are Brazil, the Mediterranean countries,
the United States and China. These countries represent more than two
thirds of global citrus fruit production.
In Sudan, the first records of citrus introduction are of the Merowe
garden in the old Dongola province which was planted in 1904 by the
governor sir Herbert Jackson pasha (Mahadi, 1979). During the early
1940's, the area of mature trees, other than lime was believed to be about
40 faddans. At the time, a great interest in citrus was developed rapidly
and fruit tree nurseries were established at Mogran, Kamlin, Kassalla,
Bara and Kadugli. Other smaller nurseries were developed at Ban-Gadid,
Abu- Gebeiha, Abbassiya, Singa and Wad ramli (Mahadi, 1979).
Consequently, the area of citrus growing expanded greatly through
intensive propagation and improved cultural practices. Citrus fruits
including oranges, grapefruits and lime are major fruit crops introduced to
Sudan over the years. They are distributed almost all over the country
(Mahmoud et al., 1996).
4
In the early seventies, several new citrus cultivars (mainly oranges and
grapefruits) were introduced from the U.S.A. They have been tested and
evaluated in different sites of the agricultural research stations. Some of
them performed very well and were officially released for the growers
(Mahmoud et al., 1996).
The sweet orange is the species grown commercially for fruit in Sudan.
In sour orange, old cultivated material is used as the traditional root stocks
for propagating citrus fruits (Mahmoud et al., 1996).
Some wild citrus trees are also reported to be growing in some parts of
western and central Sudan (Mahmoud et al., 1996). The major old
cultivars of sweet oranges (C. sinensis) include varieties like Sinari,
Beladi, Valencia, Navel and Nuri 16. The other cultivars are:
1. Naval group.
• Gillete- Frost- Parent- Thackery.
2. Valencia group.
• Campbell- Olinda.
3. Hamlin.
2.2. Uses of citrus
The fruit is commonly peeled and eaten fresh, or squeezed for its juice.
It has a thick bitter rind that is usually discarded, but can be processed into
animal feed by removing water using pressure and heat. It is also used in
certain recipes as flavouring or a garnish. Citrus are also believed to have
medicinal properties that are helpful in the fight against several diseases
(Ferguson, 2002).
5
Approximately one third of total citrus production is utilized for
processing; this proportion is higher in the case of oranges as more than
40% of globally produced oranges are utilized. In addition, oranges
account for more than 80% of total citrus utilization for processing (FAO,
1998).
2.3. Characteristics of Citrus juices
Fruit juices are products for direct consumption and are obtained by the
extraction of cellular juice fruit, this operation can be done by pressing,
blending and diffusion depending on the type of fruits.
Citrus fruits and citrus juices have several beneficial health and nutritive
properties. They are rich in Vitamin C or ascorbic acid and folic acid, as
well as a good source of fiber. They are fat free, sodium free and
cholesterol free. In addition they contain potassium, calcium, folate,
thiamin, niacin, vitamin B6, phosphorus, magnesium and copper. They
may help to reduce the risk of heart diseases and some types of cancer.
They are also helpful to reduce the risk of pregnant women to have
children with birth diseases (Economos and Clay, 1998).
2.4. Composition and nutritive value of fruit juices
The major part of the edible portion of fresh fruits consist of water (7595%most type). Fruits are poor sources of protein (0.2-1.3%as N*6.25).
But in general, contain a reasonable amount of carbohydrate. The latter
may include varying proportions of dextrose, fructose and sucrose and
possibly starch. The principal acids present in fruits are citric. Tartaric and
malic acids.
6
2.4.1. Carbohydrate
Most fruit juices are high in sugars as they contain large amounts of
dextrose and levulose and in many cases sucrose as well. Grape juice is
especially high in sugars. Concord juice ordinarily contains 16 -17 per
cent sugar; California grape juices are usually considerably higher than
this. Passion fruit juice is also very high in sugar. Sugars are important
foods, being easily digested and yielding energy quickly (Dauthy, 1995).
2.4.2. Protein
Most of the common fruits are low in protein. The loganberry is an
exception, since it contains approximately 4.5 per cent of protein (dry
matter basis). A considerable proportion of the protein content of fruits is
insoluble and consequently remains in the pomace; there-fore, most fruit
juices are very low in protein (Tressler and Joslyn, 1961).
2.4.3. Fat
Nearly all of the fruit juices are very low in fats. Grapes with 1.6%, and
blackberries and raspberries containing approximately 1% are exceptions.
Because of the small amount of fat found in fruits, their juices are
very low in fat(Tressler and Joslyn, 1961).
2.4.4. Fibers
Crude fiber is the organic residue, which remains after the food sample
has been treated under standardized conditions with petroleum spirit,
boiling dilute sulphuric acid, boiling dilute sodium hydroxide solution and
alcohol. The crude fiber consists of cellulose together with a little lignin
(Ranganna, 1977).
7
2.4.5. Acidity and pH
Organic acids contribute to the particular flavour and palatability of
orange juice and are found as a result of biochemical processes or
fermentations,
through
the
development
of
certain
spoilage
microorganisms. Acidity protects against the development of pathogens to
a large extent. In orange juice, citric acid is the most abundant, followed
by malic, both being present mostly as free acids, although in limited
quantities they are also combined as citrates or malates, which gives
orange juice its buffer effect. Other non-volatile free acids (oxalic, tartaric
and galacturonic, quinic and many others) are found in much lower
quantities (Esteve et al., 2005).
The concentration of hydrogen ions is commonly expressed in terms of
the pH scale. Low pH corresponds to high hydrogen ion concentration and
vice versa. The pH of fruits varies from 2.5- 4.5 with the range of 3-3.5
being in most type (Egan et al., 1981).
2.4.6. The total soluble solids (Brix)
Brix is a measure of the concentration of soluble solids in a solution and
is based upon the relationship between the specific gravity and soluble
solids of a pure sucrose solution, i.e. 1° Brix = 1% sugar w/w (weight to
weight). The soluble solids to acid ratio are the best criterion to determine
citrus quality.
The Brix/acid ratio which is also known as the Maturity Index alters
according to the growing regions and the effect of early and late season
fruit. The Brix and acid levels of juices are two of the most important
parameters which determine the organoleptic (taste) quality of juices.
Whilst this relationship is only strictly applicable to sucrose solutions, the
8
Brix provides a useful indication of the soluble solids of a fruit juice. The
range of extracted orange juice and grapefruit juice is 9 -12°.
Measurement of either specific gravity or refractive index is widely used
in the fruit juice and soft drink industry to provide a quick, empirical
measure of soluble solids in solution. The soluble solids content of orange
juice (exclusive of added sugars) shall be not less than 10.0% (Codex,
1981)
2.4.7. Minerals
Fruit juices are rich in potassium, and also contain much calcium,
sodium, magnesium, phosphorus, chlorine, sulfur, iron, copper and other
minerals needed by the body (Tresseler and Joslyn, 1961).
Potassium is an essential mineral that works to maintain the body's
water and acid balance. As an important electrolyte, it plays a role in
transmitting nerve impulses to muscles, in muscle contraction and in the
maintenance of normal blood pressure. The daily requirement of
potassium is approximately 2000mg. One medium orange and one 225 ml
glass of orange juice provide approximately 235 mg and 500 mg of
potassium, respectively (Whitney and Rolfes, 1999). Potassium was a
major macro mineral in orange juice ranging from 101-150 mg/100ml.
Vanderhorst et al., (1984) found that very little sodium is found in cool
drink and fruit juices.
Calcium is vital for the formation of strong bones and teeth and for the
maintenance of healthy gums. It is also important in the maintenance of a
regular heartbeat and in the transmission of nerve impulses. The amount
of calcium in raw orange juice is 11mg/100g (USDA, 2001).
9
Magnesium is necessary to prevent the calcification of soft tissue. This
essential mineral protects the arterial linings from stress caused by sudden
blood pressure changes, and plays a role in the formation of bone and in
carbohydrate and mineral metabolism. USDA, (2001) Reported that the
amount of magnesium in orange juice is 11mg/100g
The sodium (Na), potassium (K), calcium (Ca) and phosphorus (P)
content of cool drinks is low although K and P may contribute
significantly to dietary intake when most fruit juices are consumed
(Vanderhorst, et al., 1984).
2.4.8. Vitamins
Most fruit juices are excellent sources of vitamin C, several are good
sources of carotene, and many contain moderate amounts of pyridoxine,
inositol, folic acid and biotin. Vitamin C, ascorbic acid, is one of the most
important vitamins found in citrus juices, including orange juice.
Although vitamin A may be destroyed by heating, its precursor,
carotene, is much more heat stable. (Tresseler and Joslyn, 1961).
All fruits contain, more or less, anti scorbutic vitamin C. most of them
are good sources and several others are very rich in this vitamin. The
freshly pressed juices of the citrus fruits are excellent sources of this
vitamin (Tresseler and Joslyn, 1961).
According to Nagy and Smoot, (1977) often studies find that orange
juices made from frozen concentrated orange juice (FCOJ) have the
highest vitamin C levels as compared to freshly squeezed and not from
concentrate (NFC) juices. This is probably due to the fact that vitamin
C degrades over time in fresh and NFC, but doesn't degrade as much
10
in FCOJ due to it being frozen until reconstitution. If one is comparing
a NFC product that has been stored for about 3 weeks versus a newly
reconstituted FCOJ, the FCOJ would almost certainly have a higher
vitamin C concentration. Also another thing to consider is if the FCOJ is
reconstituted to the same strength as fresh or NFC. If one doesn't add
enough water, then the vitamin C (and other compounds) would be more
concentrated. Another consideration is that the vitamin C content changes
through the harvest season and orange variety also plays a part. Since
most FCOJ is blended to a larger extent than some NFCs, it is
entirely possible that the NFC is produced from a variety/season that has
a lower vitamin C content. According to Nagy and Smoot, (1977)
temperature and storage time affects the percentage of vitamin C content
of orange fruits and orange juice. Different varieties of oranges also have
different levels of vitamin C; also found that in orange juice containers,
vitamin C loss was due to oxidation by a residual air layer trapped within
the container during processing. The loss was faster in the first 2 weeks
and was more evident at higher storage temperatures. Therefore, orange
juice must be kept cool to prevent vitamin C degradation as it is
accelerated at high storage temperatures. Nagy, (1980) in his Review of
Vitamin C Contents of Citrus Fruit and Their Products, investigated what
factors affected the vitamin C contents of citrus fruits. Vitamin C levels
depend on six main factors:
1. Production factors and climate conditions.
2. Maturity state and position on the tree.
3. Type of citrus fruit (species and variety).
4. Parameters used for processing into different products.
5. Type of container.
6. Handling and storage.
11
2.5. Effect of storage on the nutritive value of juices
Fruit juices are a significant source of ascorbic acid for humans and their
consumption in the last years increased at very quick rates. However,
ascorbic acid of fruit juices is readily oxidized and lost during storage or
handling of the juices, at rates depending on the conditions of storage. It is
evident therefore that the quality of any fruit juice and its value as a
source of vitamin C depends on its content and its rate of loss upon
staying.
Retention of physical quality and palatability are the most important
criteria for determining the storage life of canned fruits. The order of
breakdown in quality of canned fruits and juices is flavor, color, texture
and nutritive losses (Irwin and Singh, 1998). The critical storage
temperature for most fruits and juices is 27-29°C, and temperature higher
than this should be limited to a few weeks.
During storage of thermally preserved fruit products, many changes
may occur that lead to deterioration in quality. The extent of these changes
depends on the processing technology, the quality of the raw material and
packaging materials and the storage conditions of the products (Lee et al.,
1977). New varieties of fruits, improved containers, more rapid
pasteurization, lower warehousing temperature, and more rapid delivery to
the ultimate consumer have all played an important part in minimizing
deterioration in storage. This deterioration is confined for the greater part,
but not entirely, to undesirable changes in flavour and appearance rather
than to changes in nutritive value. For instance, pineapple and tomato
juices change very slowly in storage; pineapple juice is generally
considered by the pineapple industry to have a shelf-life of 2 or 3 years
even when stored at the prevailing warehousing temperatures of Hawaii.
12
On the other hand, orange and apple juices are not nearly so stable and
suffer quite rapid flavor changes under common warehousing conditions
(Hulme, 1971). In juices stored at temperature, and up to 60˚ F, the change
in flavor is much less rapidly than those stored at room temperature' and
are usually acceptable after a year (Tresslar and Joslyn, 1961).
Natural juices, even kept under refrigeration, have a short shelf life
(Charalambous, 1993). Citrus juice stability depends on the raw material,
processing conditions, packaging material and storage conditions. These
factors should cause microbiological, enzymatic, chemical and physical
alterations that damage the sensorial and nutritional characteristics
(Corrêa Neto and Faria, 1999).
The sensorial aspect is directly related to consumer demand for the juice
in the search for similarity to recently processed juice (Nisida et al.,
1993). The alteration in natural juices intensifies continuously after
extraction, resulting in the development of undesirable flavour and colour
(Roig et al., 1996).
Microbial growth in citrus juice is characterized by the production of
unpleasant flavors and product deterioration that is commonly caused by
yeasts (Parish, 1991; Lima et al., 2000). Several authors have observed
that flavour quality in citrus fruits was maintained as long as appropriate
sanitization and storage temperatures to the product were used (Fellers,
1988; Tocchini et al., 1993; Pao et al., 1996). Colour and flavour indicate
the degree of fruit ripeness (Salunkhe and Kadam, 1995). Thus several
physical and chemical determinations (pH, total soluble solid content and
total titratable acidity) are important for orange juice characterization and
quality (Nisida et al., 1993).
13
Besides the chemical alterations, vitamin loss caused by temperature
increase and/or oxidation reduce product acceptance (Charalambous,
1993). The ascorbic acid content represents a stimulating factor for citrus
fruit consumption (Lee and Coates, 1987).
Storage of commercial fruit juices in closed containers at room
temperature for 4 months resulted in ascorbic acid losses ranging from 29
to 41%. Commercial orange juice when stored in open containers in the
refrigerator for 31 days lost 60 to 67% of its ascorbic acid while fresh
orange juice lost ascorbic acid at much slower rate of 7 to 13%. Open
containers of commercial fruit juice, when stored outside the refrigerator
for 10 days, lost 12.5% of their ascorbic acid content, while refrigerated
for the same period, the ascorbic acid losses amounted to 9%
(Kabasakalis et al., 2000).
2.5.1. Non-enzymatic browning
Browning reactions in foods are widespread phenomena that take place
during processing and storage (Eskin, 1990). These reactions involve
caramelization, ascorbic acid degradation and the Maillard reaction
(Clegg, 1964). Since non-enzymatic browning affects the sensory
characteristics of cooked foods such as flavour and colour (Gazzani et al.,
1987), it may be desirable in baked, fried or roasted foods (Ashoor and
Zent, 1984) as in the manufacture of coffee, tea, beer, bread and cake
(Martins et al., 2001).However, non-enzymatic browning reactions are
often responsible for important quality changes that occur during the
storage of foods, limiting their shelf-life (Buera et al., 1987). For instance,
browning is the most common quality problem of many concentrated fruit
juices (Toribio and Lozano, 1984) and causes loss of nutrients and the
formation of intermediate undesirable compounds, like furfural or 5-
14
hydroxymethyl 2-furfural (Buedo
et al., 2001). In citrus juices, non-
enzymatic browning is due to the reactions of sugars, amino acids and
ascorbic acid (Johnson et al., 1995). However, the decomposition of
ascorbic acid is reported to be the major deteriorative reaction occurring
during the storage of orange juice (Solomon and Svanberg, 1995).Lee and
Nagy (1988) also reported a high correlation between the percentage loss
of ascorbic acid and an increase in browning in grapefruit juices. On the
other hand, sugar-amino acid reactions of the classical Maillard type are
of minor importance in citrus juice browning because of the high acidity
(pH 2.0- 4.0) involved (Clegg, 1964). However, the presence of amino
acids in ascorbate systems is also considered a major contributor to the
development of browning (Robertson and Samaniego, 1986). This is
illustrated by the fact that the main degradation product of juices with pH
values below 4.0 is furfural (Huelin et al., 1971). Furfural is known to
undergo polymerization and, as an active aldehyde, may combine with
amino acids and contribute to the browning of the juice (Solomon et al.,
1995). Likewise, HMF concentration has a high correlation with the level
of browning in lemon juice and therefore plays an important role in the
formation of brown pigments (Robertson and Samaniego, 1986).
2.6. Orange juice
Orange juice is a fruit juice obtained by squeezing or pressing the
interior of an orange. It is enjoyed as a beverage in many parts of the
world; Orange juice is defined in the United States Code of Federal
Regulations as the "unfermented juice obtained from mature oranges of
the species Citrus sinensis or of the citrus hybrid commonly called Amber
sweet."(Nelson and Tressler, 1980).
15
The major feature of the world market for orange juice is the
geographical concentration of production. There are only two main
players: the State of Florida in the United States and the State of Sao
Paulo in Brazil. Production of orange juice between these two players
makes up roughly 85 percent of the world market. The major difference
between them is that Brazil exports 99% of its production while 90%
of Florida’s production is consumed domestically and only 10 % is
exported. International
trade in orange juice takes place in the form of
frozen concentrated orange juice (FCOJ), in order to reduce the volume
used, so that storage and transportation costs are reduced (FAO, 1998).
2.6.1. Types of orange juices
Orange juice can be presented in different forms. The major types of
orange juice are the following:
2.6.1.1. Freshly Squeezed Orange Juice
The juice is squeezed from fresh fruit and packaged in paper cartons,
glass or plastic containers, without being pasteurized. The product is
clearly labeled and located in the produce or dairy section of the grocery
store, with a shelf life of only a few days. It is also typically
made at
home (Matthews, 1994).
2.6.1.2. Frozen Concentrated Orange Juice
Frozen Concentrated Orange Juice (FCOJ) is the most widely traded as
a commodity in the International market, normally at 65º Brix. FCOJ is
obtained by removing, through evaporation, the water from the orange
juice of fresh, ripe oranges that have been graded, sorted, washed and
squeezed in extraction machines. It is then stored at 20ºF or lower until it
16
is sold or packaged for sale. FCOJ is seven-to-one strength ratio to normal
single-strength orange juice (Matthews, 1994).
Consumers reconstitute the FCOJ at home by adding water to the
concentrate. At one time this used to be the dominant type of orange juice
sold in the United States. However, due to increasing consumer preference
for more convenient ready-to-drink orange juice, FCOJ has lost its
supremacy. FCOJ can be stored for several years at the adequate
temperature (Matthews, 1994).
2.6.1.3. Not-From-Concentrate Orange Juice
Not-from-concentrate orange juice (NFC) is processed and pasteurized
by flash heating immediately after squeezing the fruit, without removing
the water content from the juice. NFC is never concentrated (Binkley,
2001).Demand for NFC has been steadily increasing in North America
and in Europe since the nineties. NFC is perceived as the closest match
to freshly squeezed juice in flavour, offering a convenient ready-to
serve package that is easier to use than frozen orange juice, but its
Transportation costs are higher. The quality of NFC is considered to be
higher than that of other types of orange juice (Binkley, 2001).
2.6.1.4. Refrigerated Orange Juice from Concentrate
Refrigerated Orange Juice from Concentrate (RECON) is a juice that
has been processed to obtain the frozen concentrate and then reconstituted
by adding back the water that had been originally removed. Reconstituted
single strength juice is normally reconditioned by the packager or the
beverage industry and sold as a ready-to-serve product either in chilled
form or in aseptic form sold in bottles or cartons without the need of
refrigeration (Binkley, 2001).
17
2.6.2. Orange Juice processing
A blend of different popular types of oranges is generally used to
provide a specific flavour and to ensure freedom from bitterness. Selection
of oranges for juice is made on the basis of a number of factors such as
variety and maturity of the fruit. The fruit contains a number of natural
materials that contribute to the overall flavour and consistency of the
juice including water, sugars (primarily sucrose, fructose, and glucose),
organic acids (primarily citric, malic, and tartaric), and flavour
compounds (including various esters, alcohols, ketones, lactones, and
hydrocarbons) (Nelson and Tressler,1980).
There are several food additives allowed in the orange juices processing
such as sulfur dioxide or sodium benzoate are allowed by federal
regulation in orange juice although the amounts are strictly controlled.
Similarly, ascorbic acid, alpha tocopherol, EDTA, BHA, or BHT are used
as antioxidants. Sweeteners may be added in the form of corn syrup,
dextrose, honey, or even artificial sweeteners. More often, though, citric
acid is added to provide tartness. Manufacturers may also fortify juices
with extra vitamins or supplemental nutrients such as vitamin C, and less
commonly, vitamins A and E, beta carotene and Calcium is also
frequently added to orange juice (Nelson and Tressler, 1980).
Mature orange fruits are harvested, shipped to orange juice plant
inspected and graded before it can be used. An inspector takes a sample to
analyze in order to make sure that the fruit meets maturity requirements
for processing. The certified fruit is then transported along a conveyor belt
where it is washed with a detergent as it passes over roller brushes. This
process removes debris and dirt and reduces the number of microbes. The
fruit is rinsed and dried. Graders remove bad fruit as it passes over the
18
rollers and the remaining quality pieces are automatically segregated by
size prior to extraction. Proper size is critical for the extraction process
(Nelson and Tressler, 1980).
Proper juice extraction is important to optimize the efficiency of the
juice production process as well as the quality of the finished drink.
Extraction has the oranges cut in half before the juice is removed. The
fruits are sliced as they pass by a stationary knife and the halves are then
picked up by rubber suction cups and moved against plastic serrated
reamers. The rotating reamers express the juice as the orange halves travel
around the conveyor line. Some of the peel oil may be removed prior to
extraction by needles which prick the skin, thereby releasing the oil which
is washed away. Modern extraction equipment of this type can slice, ream,
and eject a peel in about 3 seconds. (Nelson and Tressler, 1980).
The extracted juice is filtered through a stainless steel screen before it is
ready for the next stage. At this point, the juice can be chilled or
concentrated if it is intended for a reconstituted beverage. If a NFC type, it
may be pasteurized.
Concentrated juice extract is approximately five times more
concentrated than squeezed juice. Concentration is useful because it
extends the shelf life of the juice and makes storage and shipping more
economical. Juice is commonly concentrated with a piece of equipment
known as a Thermally Accelerated Short-Time Evaporator (TASTE).
TASTE uses steam to heat the juice under vacuum and force water to be
evaporated. Juice concentrate is then stored in refrigerated stainless steel
bulk tanks until is ready to be packaged or reconstituted.
19
When the juice processor is ready to prepare a commercial package for
retail sale, concentrate is pulled from several storage batches and blended
with water to achieve the desired sugar to acid ratio, colour and flavour.
This step must be carefully controlled. Proper blending of juice
concentrate and other flavour fractions is necessary to achieve a high
quality flavour (Nelson and Tressler, 1980).
Characteristically orange juice has low pH (about 4), as such it has some
natural protection from bacteria, yeast and mould growth. However,
pasteurization is still required to further retard spoilage. Flash
pasteurization minimizes flavour changes from heat treatment and is
recommended for premium quality products. Several pasteurization
methods are commercially used. One common method passes juice
through a tube next to a plate heat exchanger, so the juice is heated
without direct contact with the heating surface. Another method use hot,
pasteurized juice to preheat incoming unpasteurized juice. The preheated
juice is further heated with steam or hot water to the pasteurization
temperature. Typically, reaching a temperature of 85-94° C for about 30
seconds is adequate to reduce the microbe count and prepare the juice for
filling (Nelson and Tressler, 1980).
The pasteurized juice should be filled while still hot to ensure the
sterility. Where possible, metal or glass bottles and cans can be preheated.
Packaging which can not withstand high temperatures must be filled in a
sterile environment. Instead of heat, hydrogen peroxide or another
approved sterilizing agent may be used prior to filling. The empty
packages are filled from bulk storage juice's tanks. The filling head meters
the precise amount of product into the container, and depending on the
design of the package, it may immediately invert to sterilize the lid. After
filling, the containers are cooled as fast as possible. Orange juice
20
packaged in this manner has a shelf life of 6-8 months at room
temperature (Nelson and Tressler, 1980).
2.6.3. Quality Control
Quality is checked throughout the production process. The most
important measurement in orange juice production is the sugar level,
which is measured in degrees Brix (percentages by weight of sugar in a
solution). The types of oranges used and the climate in which they were
grown affect the sugar level. Manufacturers blend juices with different
sugar levels together to achieve a desired sugar balance. The final juice
product is evaluated for a number of key parameters which include
acidity, citrus oil level, pulp level, pulp cell integrity, colour, viscosity,
microbiological contamination, mouth feel, and taste. A sensory panel is
used to evaluate subjective qualities like flavour and texture. Lastly during
the filling process, units are inspected to make sure they are filled and
sealed appropriately (Nelson and Tressler, 1980).
2.6.4. Microbiology of orange juice
Citrus products are marketed as fresh or reconstituted single strength
juices and as frozen concentrates; none are sterile. The degree of
contamination varies depending upon how the fruit was handled from the
field and in the processing plant. During processing, some bacteria may
develops in juice and juice concentrates especially Lactobacillus spp. and
Leuconostoc spp and Lactobacillus spp. (Dauthy, 1995). Bockelmann
(1998) reported that the main spoilage organisms in juices are yeasts and
moulds. Yeasts are primarily responsible for spoilage of chilled juice that
is not sterile. Most industrial juice concentrators use a high temperature
evaporator (thermal accelerated short time evaporation) and microbes are
21
generally killed during the process. Many of the survivors should be killed
by the freezing process even though this process will preserve the ultimate
survivors. Coliforms are rare in fruit juices.
2.6.5. Nutritional and health benefits of orange fruit and juice
Besides its high nutritional value and sensorial properties, orange juice
has been recognized to have a potential protective action against certain
degenerative diseases. According to recent epidemiological studies, high
consumption of orange juice is associated with a reduced risk of oxidative
damage related to the presence of free radicals and also to reduced risk of
contracting different types of cancer, cardiovascular and neurological
diseases. This has been mainly attributed to the significant number of
antioxidants naturally present in orange juice (Dip lock, 1994; Hollman
et al., 1996; Kaur & Kapoor, 2001; Landbo & Meyer, 2001; Vinson et al.,
2002).
* Orange is an excellent food in all types of fevers like typhoid and
measles; it gives energy, increases urinary output and
promotes body
resistance against infections, thereby helping to recover fast.
*Orange is a good food remedy in chronic dyspepsia. It gives rest to
the digestive organ and supplies nutrition in the most easily assimilable
form. It also stimulates the flow of digestive juices thereby improving
digestion and increasing appetite.
*Taking one or two oranges at bed time and again on getting up in the
morning, is an excellent way of stimulating the bowel action, thus
removing food residue from the colon which may cause putrefaction and
intoxication.
22
*Being a good source of calcium and vitamin C, orange works well in
the diseases of the bone and teeth. Many patients of pyorrhoea and dental
caries have been cured by taking large amounts of orange juice.
* Orange juice is considered to be the best food for infants if given
daily. It prevents scurvy and rickets and helps growth. It is good for babies
whose normal development is retarded for some cause.
* The use of orange mixed with a pinch of salt and a tablespoon of
honey is effective remedy for asthma, common cold, bronchitis and
another condition of cough associated with difficult expectorations. It
eases expectorations and protects from secondary infections.
2.7. Consumption of fruits and fruit juices in Sudan
Citrus fruits are mainly consumed in developed countries, although
consumption per capita is increasing in developing countries as levels of
income increase. There seems to be certain stagnation of citrus fruits
consumption in developed countries. According to FAO, 2003 fresh
orange consumption is declining in developed countries mainly due to
two reasons: it is being replaced by orange juice consumption and
improvements in transportation and storage favor wider and longer
availability of substitute fruits. However, fresh orange consumption
expanded in many developing countries, especially in emerging
economies such as Mexico, India, Argentina, Brazil and China.
The institute for monetary and economic studies (IMES) consulting
limited (UK) studied the Sudan market and prepared a report entitled
"overview of selected dairy products and juice beverages in Sudan, 2002".
(Alrikain, 2004). According to the aforementioned report up to 1995 the
23
market for commercial, packaged juice products in Sudan has remained
small (volume =0.2 millions) due to use of squeeze fresh juice at home or
purchase from juice stalls by cup. The limited packaged juice products
locally-produced low quality concentrated drinks, sold in plastic
containers or glass bottles and another reason. From 1997 new companies
started producing well-packaged juice drinks that lead to the increase in
the consumption volume from 0.3 to 0.7 millions liter. The consumption
increase continued at steady rate to the year 2000. The growth rate
reached its peak (130%) in 1997 and then dropped to 29% in the next
year. Growth became stable after that and expected to increase at steady
rate in the following years. The consumption Per capita showed
significant increase in 1997 and then continued until reached 52.00
millions liters in the year 2000 and expected to increase through the
following years at steady rate.
24
Chapter Three
MATERIALS AND METHODS
The present study was carried out to test the physico-chemical and
sensorial stability of unpasteurized orange juice (processed at home) and
commercial orange drinks from local processing company in both market
conditions storage i.e. refrigeration and room temperature.
3.1. Materials
Samples of natural orange drinks were supplied by a local beverage
factory located in Khartoum state. A sample batch of 40 drinks bottles i.e.
plastic bottles were taken directly from the processing line. Three bottles
were analyzed immediately for proximate composition, chemical analysis
(pH, titratable acidity, total soluble solids and ascorbic acid) and sensory
evaluation. The others were stored in equal portions both at the room
temperature and refrigerated temperature for three months in market
conditions.
Samples of unpasteurized natural orange juice extracted from local
orange fruit and processed at home using a small-size juicer and stored in
plastic bottles. After extraction, the samples were stored for 72h under
different conditions; juice samples were stored under two isothermal
conditions at the room temperature and refrigerated temperature. The
samples were characterized for ascorbic acid contents, complementary
chemical analyses and sensorial analyses were applied.
Samples were evaluated at zero time and at regular time intervals
depending on the experimental design, for a period of at least 3 months for
25
natural orange drink and 3 days for the fresh orange juice, depending on
storage temperature.
3.2. Methods
3.2.1. Proximate composition
Moisture content (MC) of each sample was determined according to the
standard official method of analysis (AOAC, 1995).The moisture content
was calculated as shown blew.
Calculation:
MC (%) =
W1 -
W2
× 100
W1
Where:
W1 = weight of sample before drying.
W2 = weight of sample after drying.
Crude fiber of each sample was estimated according to the method
described by AOAC, (1995). Two grams of defatted sample were
digested in 200ml boiling 0.255N H2SO4 under reflux condenser, for
30minutes. Then filtered under suction using a linen piece as filter
medium. The residue was washed with hot water to remove any trace of
acid. A second alkali digestion was done using 200ml boiling 0.344N
NaoH for 30minutes, and then similarly filtered as above. The residue
was washed with hot water, dried at 105◦c overnight and then re weight.
The crude fiber (CF) was calculated using the formula.
26
CF% =
W¹ - W² × 100
Wº
Where:
W¹ = The weight of the crucible plus sample before ignition.
W² = The weight of the crucible plus sample after ignition.
Wº = The weight of dried sample.
Total nitrogen of the sample, was estimated using the kjeldhal digestion,
distillation and titration method, as described by the official methods of
analysis (AOAC, 1995). About 0.2g of sample were weighed into 100 ml
Kjeldhal flask, then
0.4g of the mixture catalyst (cupric sulphate +
sodium or potassium sulphate) and about 3.5 ml of concentrated sulphuric
acid were added. The sample and contents were heated on an electric
heater for 2 hrs with gradual increase of heating temperature. After
complete digestion the sample was left to cool, diluted and placed in the
distillation apparatus. About 20 ml. of 40% NaOH were added and
distilled for 7 min. The ammonia evolved was received in 10 ml of 2%
boric acid solution containing 3 drops of mixed indicator (bromocresol
green and methyl red). The trapped ammonia was titrated against 0.02N
HCl.
The crude protein content (CP) was calculated by multiplying the percent
of nitrogen by protein conversion factor (N % x.6.25).
Calculation:
27
N (%) =
(A – B) × N × 14 × 100
1000 × S
CP (%) = N% × 6.25
Where:
A
= ml of Hcl for sample titration.
B
= ml Hcl of blank sample.
N
= normality of HCL.
14
= equivalent weight of nitrogen.
S
= original weight of sample.
1000 = number of milligrams in one gram.
6.25 = protein conversion factor
Crude oil (CO) of sample was determined using the official methods of
analysis (AOAC, 1995) the crude oil was estimated using Soxhlet
apparatus. Crude oil was calculated by the following equation
CO% =
W2 - W 1
×100
Wº
Where:
W1= weight of empty receiver
W2= weight of receiver +oil
W0 = weight of dried sample
28
Total ash of sample was estimated according to the official methods of
analysis (AOAC, 1995). The ash content was calculated using the
formula:
Ash% =
W¹ - W²
× 100
Wº
Where:
W1= original weight of sample
W2= weight of sample after ignition
W0 = weight of dried sample
Total carbohydrates (TC) were calculated subtracting the value of
protein, oil, fiber, Ash and moisture content from 100
TC (%) = 100 – [MC (%) + CF (%) + CP (%) + CO (%) + Ash (%)]
3.2.2. PH value
The pH value of the samples were determined with a glass electrode pH
– meter (Karl kolb, D-6072 Dreieich) at room temperature.
29
3.2.3. Titratable acidity (T.A.)
Ten ml of samples were titrated against 0.1N Sodium hydroxide, using
phenolphthalein as an indicator (Egan et al., 1981). T.A. expressed as
citric acid.
Calculation:
T.A. (Mg/100g) = (ml of NaOH)(N. NaOH) (Equiv. wt. of acid) 100
1000 (wt.of sample)
3.2.4. Total soluble solids (TSS)
Total soluble solids was determined using a hand refractometer;
expressed as Brix degree.
3.2.5. Ascorbic Acid
The method of Lees, (1975) was employed, which involves the following
steps:
a. A 10 ml aliquot of sample is placed into a 100 ml volumetric flask and
brought to volume with 0.4% oxalic acid solution.
b. The solution is filtered through a Whatman No. 4 filter paper.
c. A 10 ml aliquot of the filtered solution is pipetted into a conical flask
along with 15 ml of 0.4% oxalic acid solution.
d. Solution in (c) is titrated, using a microburette, with 0.04% aqueous
2-6- dichlorophenolindophenol solution to the first pink shade.
30
3.2.6. Minerals
Potassium and Sodium contents of each extracted sample were
determined according to the Standard Official Methods of Analysis
(AOAC 1995) using corning 400, flame photometer.
One ml of the extract was taken and diluted in a 50 ml conical flask with
distilled water. The standard solutions of the KCL and NaCL were
prepared by dissolving 2.54, 3.33g of KCL and NaCL respectively, each
in 1000 ml distilled water. Ten mls of this solution were taken and diluted
with 1000 ml distilled water to give a 10 ppm concentration. The flame
photometer was adjusted to zero degree using distilled water as a blank
and to 100 degree using standard solution.
Calculations of the alkaline metals were as follows;
K or Na (%) = [F.R x D.F x 100]
103 x S x 10
Where:
F.R
= flame photometer reading.
D.F
= dilution factor.
S
= sample weight.
Calcium and magnesium determinations were carried out for each
samples extract according to Chapman and Pratt (1968). Calcium was
determined by taking 2 ml of the extracted sample and placed in a 50 ml
conical flask. Ten mls of distilled water were then added to the contents in
the flask. Three to four drops of 4N NaOH were mixed with small amount
of meroxide indicator (0.5g of ammonium purpurat was mixed with 100g
31
of powdered K2SO4) giving a pink colour. The contents of the flask were
titrated with 0.01N EDTA (ethylene diamine tetra-acetic acid) until a
violet color, indicating the end point was obtained.
Calcium and magnesium were determined together by taking 2 ml of the
extract in 50 ml conical flask. Twenty ml of distilled water, 10 drops of
buffer (6.75g ammonium chloride in 57 ml conc. ammonia diluted to 100
ml with distilled water) and 3-4 drops of eriochrome black T (E.B.T)
indicator (0.1g eriochrome + 0.9g hydroxylamine hydrochloride were
dissolved in 20 ml of about 95% ethanol) were added to the extract giving
purple colour. The mixture was titrated with 0.01N E.D.T.A until a blue
colour indicating the end point was reached. The magnesium content was
estimated by subtracting the Ca content from (Ca + Mg) content as
follows:
Calculation:
Ca or Mg (%) = [T.R x N (EDTA) x D.F x M.wt x 100]
106 x S x 2 x valency
Where:
T.R
= titration reading.
N (EDTA)
= normality of EDTA.
D.F
= dilution factor.
M. wt
= molecular weight of the elements estimated.
S
= sample weight.
Valency
= Mg or Ca
32
3.2.7. Sensory analysis
An informal panel of Ten untrained assessors evaluated the samples on
the basis of degree of acceptability for colour, taste, aroma and overall
acceptability using a scale ranging from 1 to 5, as follows: (1) taste (5,
very good taste; 4, good; 3, acceptable; 2, poor; 1, very poor taste); (2)
colour: (5, very good; 4, good; 3, acceptable; 2, bad colour; 1, very bad
colour); (3), overall acceptability (5, very good; 4, good; 3, acceptable; 2,
bad; 1, very bad); and (3), aroma (5, very good; 4, good; 3, acceptable; 2,
off-flavoured; 1, strongly off-flavoured). In all classifications we fixed the
limit of acceptability at 3 points.
3.2.8. Statistical analysis
The data obtained were subjected to the analysis of variance and
whenever appropriate the mean separation procedures of LSD were
employed (Steel and Torrie, 1980).
The statistical analysis system program (SAS institute, 1988) was used
to perform the general linear model, GLM, analysis.
33
Chapter four
RESULTS AND DISCUSSION
4.1. Orange drink
4.1.1. Proximate composition
The moisture content of refrigerated natural orange drink did not change
(p ≥0.05) in the first two weeks of storage. From there after it decreased
progressively with the increase in the storage period (Table 1). As shown
in Table 2 it is clear that moisture content of orange drink did not show
significant decrease except at 4 weeks. The effect is more pronounced at 8
and 12 weeks under refrigerated and room temperature storage conditions.
With lower moisture contents at room temperature storage. This decrease
in moisture content may be due to hydrolysis of sucrose to reducing sugar
(Khurdiya and Anand, 1981).
In the first two weeks of storage period of refrigerated natural orange
drink the crude fiber decreased by about 23% (Table1), but from 4 weeks
storage period until the end of storage period the results indicated no
significant change in the crude fiber values of natural orange drink was
stored at refrigerator temperature. In the first 2 weeks of storage period the
crude fiber content of natural orange drink stored at room temperature did
not show a significant change. It had a crude fiber similar to that of wk 0.
But from 4 weeks of storage period until the end of the experiment the
results indicated a significant decline in the crude fiber values for natural
orange drink stored at room temperature (Table 2).
34
Table (1): The effect of refrigerated storage on the proximate
composition of orange drink.
Parameters
(%)
Storage Period(weeks)
0
2
4
8
12
Moisture
87.83a
87.85a
87.51b
86.85c
86.54d
Fiber
0.09a
0.07b
0.071b
0.07b
0.068b
CHO
11.62d
11.63d
11.98c
12.66b
12.98a
Protein
0.16a
0.16a
0.14b
0.13c
0.12d
Fat
0.23a
0.23a
0.23a
0.23a
0.22a
Ash
0.07a
0.07a
0.07a
0.07a
0.07a
CHO= carbohydrates.
Means in the same row bearing different superscript letters are significantly
different (p < 0.05).
n=3
35
Results indicate non significant changes in carbohydrate values of the
natural orange drinks stored under refrigerator (Table1) and room
temperature (Table2). At 4 weeks storage under refrigerated temperature
there was a significant increase in the original carbohydrate value from
11.63% to 11.98%. Also at room temperature the carbohydrate was
significantly increased at the same period. A significant increased in
carbohydrate values of natural orange drinks were also observed for the
4wks, 8wks and 12wks storage periods in both refrigerated temperature
and room temperature storage conditions.
The 2 weeks storage period for natural orange drink at refrigerated
temperature (Table1) the crude protein value did not change, but in natural
orange drink stored at room temperature condition (Table2) the crude
protein recorded slight decrease. Four weeks storage period had a
significant decrease in the crude protein value at both room and
refrigerated condition; however this decrease in crude protein values were
continual at both conditions until the end of storage period (12 weeks).
The crude oil of refrigerated natural orange drink (Table1) did not
change with the storage period; however it experienced a slight decrease
at the end of storage period (12 weeks). A similar effect was pronounced
at 12 weeks when storing under room temperature (Table 2). Both
samples of orange drink stored under refrigeration and room temperature
did not show changes in ash content (Table 1 and 2).
36
Table (2): The effect of room temperature storage on the proximate
composition of orange drink.
Parameters
(%)
Storage Period (weeks)
0
2
4
8
12
Moisture
87.83a
87.80a
87.55b
86.80c
86.32d
Fiber
0.09a
0.085a
0.082b
0.073c
0.062d
CHO
11.62d
11.67d
11.93c
12.69b
13.19a
Protein
0.16a
0.15b
0.14c
0.14c
0.13d
Fat
0.23a
0.22a
0.23a
0.23a
0.21a
Ash
0.07a
0.07a
0.07a
0.07a
0.065a
CHO= carbohydrates.
Means in the same row bearing different superscript letters are significantly
different (p < 0.05).
n=3
37
4.1.2. pH value
The effects of storage period and temperature on the pH value of orange
drink is shown in Fig. 1 the pH value of orange drink at the beginning of
the storage period was 3.85. This value is with in the range of 3.2-4.3,
reported by Ashurst et al., (1998).
The results of pH values indicated significant changes (p ≤0.05) during
storage at room and refrigerated temperature.
In the early stages of storage i.e. at 2 weeks, the pH value of natural
orange drink stored at both temperatures under investigation, i.e.
refrigeration and room temperature increased significantly (p ≤0.05) over
that at the beginning of storage period (Fig.1). The value of increase was
about 0.1- 0.12 pH units. It was noticed that the highest increase in pH
was that for the natural orange drink stored at room temperature.
From 2 week storage period onward, the pH of natural orange drink for
both samples stored at refrigerator and room temperatures decreased
gradually to reach the lowest pH values (Fig.1) at the end of the storage
period (12weeks). Also it should be noted that at this storage period the
natural orange drink stored at refrigerator temperature had higher pH
values than that stored at room temperature.
4.1.3. Titratable Acidity
The titratable acidity value for orange drink was 1.29% at zero weeks.
Egan et al. (1981) reported that the titratable acidity for orange juice
ranged between 0.4 – 3.5% which agrees with the present result. The
results of titratable acidity values indicated significant changes during
storage for orange drinks at room and refrigerated temperatures.
38
It is clear from the results in Fig. 2 that a significant decrease in titratable
acidity was observed at (p ≤0.05) for both natural orange drink samples
stored at refrigeration and room temperature conditions. At 4 weeks
storage period a significant increase at the same propability level was
shown for both samples. The effect is more pronounced at longer storage
periods as clear in the figure. This trend of increase in titratable acidity is
similar to the results of Ziena, (2000).
39
4
3.95
pH value
3.9
3.85
3.8
3.75
3.7
3.65
3.6
3.55
0
2
4
8
12
Storage (weeks)
Refrigerated sample
Room temp. sample
Figure 1: The effect of storage period and temperature on the
pH value of orange drink.
40
1.4
T.A. value
1.35
1.3
1.25
1.2
1.15
1.1
0
2
4
8
12
Storage (weeks)
Refrigerated sample
Room temp. sample
Figure 2: The effect of storage period and temperature on the
titratable acidity (T.A.) of orange drink.
41
4.1.4. Total soluble solids
The effect of storage temperature and period on total soluble solids of
orange drink is shown in Figure (3). At the beginning of storage period
total soluble solids for orange drink was found to be 11.7 °Brix.
FAO/WHO, (1992) recommended that the total soluble solids for orange
juice (exclusive of added sugars) shall be not less than 10%. Up to 4weeks
of storage at refrigeration temperature, total soluble solids of orange drink
were similar to the value at the beginning of storage. From the 8th wk of
storage period till the end (12wks), TSS of refrigerated orange drink
showed substantial increase compared to those at the start of storage
period. The total soluble solids of natural orange drink stored at room
temperature showed gradual increase from the 2nd wk of storage till the
end.
4.1.5. Ascorbic Acid
The effects of both storage period and storage temperature on the
ascorbic acid of natural orange drink are depicted in Figure (4).
The content of ascorbic acid for natural orange drink was found to be
30.51mg/100ml at the beginning of storage period. Such ascorbic acid
content for natural orange drink reported here was within the range of 2080mg/100ml reported by Egan et al., (1981).
Ascorbic acid results have shown significant changes (p ≤0.05) during
storage period at refrigerated and room temperature for natural orange
drinks. The ascorbic acid content for natural orange drink stored for 2wks
at
refrigerated
temperature
(Fig.4)
decreased
significantly
from
30.51mg/100ml to about 25mg/100ml. Also the natural orange drink
stored at room temperature condition (Fig.4) showed a similar significant
42
decrease (p ≤0.05) in ascorbic acid content. The ascorbic acid content of
refrigerated natural orange drink and that stored at room temperature
decrease significantly with the increase in the storage period. This
decrease continued in till the end of storage period.
The overall decrease in ascorbic acid content of natural orange drink
stored at refrigeration or room temperature had mounted to about 52% and
59% respectively. Obviously ascorbic acid is quite sensitive to external
conditions particularly storage temperature.
Ascorbic acid loss trend in this study are in agreement with the findings
of several investigators working on citrus juices (Kabasakalis et al., 2000;
Laing et al., 1978; Lee and Nagy, 1988; Nagy and Smoot, 1977) or tomato
juice (Lee et al., 1977). However its magnitude is quite different from that
reported by Kabasakalis et al. (2000). The latter investigator reported
losses in ascorbic acid at room temperature ranging from 29 to41% in 4
month time (i.e. 16wks) while in the current study we reported loss of
59% for the same storage conditions (i.e. at room temperature) for(12
wks). On the other hand, commercial orange juice when stored in open
containers in the refrigerator for 31 days lost 60 to 67% of its ascorbic
acid (Kabasakalis et al., 2000).
43
12
11.95
11.9
TSS value
11.85
11.8
11.75
11.7
11.65
11.6
11.55
0
2
4
8
12
Storage (weeks)
Refrigerated sample
Room temp. sample
Figure 3: The effect of storage period and temperature on the
total soluble solids (TSS) of orange drink.
44
35
30
Ascorbic acid value
25
20
15
10
5
0
0
2
4
8
12
Storage (weeks)
Refrigerated sample
Room temp. sample
Figure 4: The effect of storage period and temperature on the
ascorbic acid of orange drink.
45
4.1.6. Minerals
At the beginning of storage the minerals content for natural orange drink
were, potassium (K) 2.3 mg/L, sodium (Na) 1.6 mg/L, calcium (Ca) 36
mg/L and magnesium (Mg) 14 mg/L. (Table 3). In the first two weeks of
refrigerated storage, none of the minerals tested i.e. Na, K, Ca and Mg
showed any change (Table 3). With the increase in storage period the
change in mineral content differed from one mineral to the other. On the
4th wk of refrigerated storage, the K content of refrigerated orange drink
differed significantly (p ≤0.05) from that at the beginning of the
experiment, showing a reduction of about 6.5% from week 4 to 8. At 12
week K content of refrigerated orange drink did not show any change
(p ≥0.05).
The sodium content of refrigerated orange drink (Table 3) did not change
with the storage time (p ≥0.05).
The Calcium content of refrigerated natural orange drink (Table3)
decreased significantly (p ≤0.05) with storage period. On the 4th wk, the
Ca content of natural orange drink was significantly (p ≤0.05) lower than
that at the start of the experiment. No change was observed in the Ca
content of refrigerated orange drink between week 4 and 8 of storage,
however at the end of the storage period (12 wks) the Ca content was
significantly lower (p ≤0.05) than that of wk 4 or wk 8 of storage. The
overall reduction in the Ca content throughout the storage period had
mounted to about 10%.
The magnesium content of refrigerated natural orange drink (Table3)
decreased significantly (p ≤0.05) with storage period.
46
The natural orange drink stored at room temperature (Table4) showed
significant decrease in potassium content during storage period mounted
to about 30% at the end.
Sodium content of natural orange drink stored at room temperature did
not change (p ≥0.05) with the storage period (Table 4).except after 12 wks
storage.
Calcium content of natural orange drink stored at room temperature
(table4) decreased significantly (p ≤0.05) with storage period.
Similarly the magnesium content of natural orange drink stored at room
temperature (Table4) decreased significantly (p ≤0.05) with storage
period. Within each storage period, the natural orange drink stored at
room temperature had continually lower potassium, Calcium, magnesium
contents than the refrigerated natural orange drink.
Regardless of the storage temperature or period. The mineral contents
reported in this study were far less than those reported by Whitney and
Rolfes (1999) and USDA. (2001). Whitney and Rolfes, (1999) reported a
value of 101-150 mg/100ml for potassium where as in this study it is
0.23mg/100ml. for calcium and Mg USDA, (2001) reported 11mg/100ml.
in the current study they were 3.6 mg/100ml and 1.4mg/100ml,
respectively.
47
4.1.7. Sensory evaluation
Table 5 shows the effects of storage temperature and period on the
sensory properties of natural orange drink. The samples were evaluated at
the beginning and at the end of storage period (12weeks). The visual
colour scores of natural orange drink stored at refrigerated temperature
were significantly higher than that stored at room temperature for the
same storage period (12wks). Indicating that panelists prefer the color of
refrigerated natural orange drink. Within each temperature the visual color
of natural orange drink is affected by the storage period. The aroma and
overall acceptability scores of natural orange drink stored at refrigerated
temperature were significantly higher than the aroma and overall
acceptability scores of natural orange drink stored at room temperature for
the same storage period (12wks). That means the panelists prefer the
aroma and overall acceptability of refrigerated natural orange drink.
Sensory evaluation of stored natural orange drink revealed that
refrigerated natural orange drink had significantly higher taste scores than
that stored at room temperature for the same storage period (12wks).
Hulme, 1971 indicated that orange juices are not nearly so stable and
suffer quite rapid flavour and nutrient changes under common storage
condition. Also Charalambous, (1993) and Correa neto and Faria (1999)
indicated that storage conditions are one of the factors that could cause
chemical and physical alterations that may degrade the nutritional and
sensorial characteristics of orange juice.
48
Table (3): The effect of refrigerated storage on the Minerals
(K - Na – Ca– Mg) of orange drink.
Storage Period(weeks)
Parameters
0
2
4
8
12
Potassium
mg/ L
2.3a
2.3a
2.15b
2.15b
2.10b
Sodium
mg/ L
1.6a
1.6a
1.6a
1.6a
1.6a
Calcium
mg/ L
36.0a
35.8a
33.25b
33.3c
32.6d
Magnesium
mg/ L
14a
13.9a
13b
13b
13b
Means in the same row bearing different superscript letters are significantly
different (p < 0.05).
n=3
49
Table (4): The effect of room temperature storage on the Minerals
(K - Na - Ca - Mg) of orange drink.
Parameters
Storage Period(weeks)
0
2
4
8
12
Potassium
mg/ L
2.3a
1.8b
1.8b
1.6c
1.6d
Sodium
mg/ L
1.6a
1.6a
1.6a
1.6a
1.5b
Calcium
mg/ L
36.0a
35.75b
34.70b
34.44c
34.1d
14a
13.35b
13c
12.7d
Magnesium
12.7d
mg/ L
Means in the same row bearing different superscript letters are significantly
different (p < 0.05).
n=3
50
Table (5): The effect of storage period and temperature on the sensory
properties of orange drink stored for twelve weeks.
*SP
Temp.
0
Colour
Aroma
Taste
Overall
acceptability
4.40a
4.20a
4.50a
4.30a
12
*1
3.30b
3.00b
3.10b
3.10b
12
*2
2.90c
2.20c
2.00c
1.80c
*SP= Storage period in weeks, *1= Refrigerated temp., *2= Room temp.
Means in the same row bearing different superscript letters are significantly different
(p < 0.05).
n=3
51
4.2. Fresh orange juice
4.2.1. Proximate composition
The proximate composition of natural orange juice stored at refrigerated
or at room temperature are shown on Table 6 and 7 respectively. With the
exception of carbohydrate content, none of the parameters measured i.e.
moisture, fiber, protein, oil and ash contents, was affected (p ≥0.05) by the
storage conditions investigated. Carbohydrate values of the orange juice
stored under refrigerated temperature (Table6) or room temperature
(table7) decreased with the increase in storage period. Carbohydrates
dropped (p ≤0.05) from 10.04% to 9.51% (Table6) and from 10.04% to
9.68% (Table7) for natural orange juice stored at refrigeration or room
temperatures.
4.2.2. pH value
The pH value for the orange juice was 4 at the beginning. The pH values
of the juice were within the normal range (3.2–4.3) reported by Ashurst et
al., (1998) and the differences according to storage period are highly
significant (p ≤0.05), with the exception of the differences between juices
stored at refrigerated temperature (Table8) and room temperature (Table9)
conditions in the end of storage period (3days). The results of pH values
indicated significant decrease during storage at room and refrigerated
temperature. The decrease in pH may be due to the increase in the
titratable acidity.
52
Table (6): The effect of storage period at refrigeration temp. on
the proximate composition of natural orange juice.
*SP
Moisture
(%)
Fiber
(%)
CHO
(%)
Protein
(%)
Oil
(%)
Ash
(%)
0
89.63a
0.06a
10.04a
0.11a
0.12a
0.05a
3
90.17a
0.06a
9.51b
0.11a
0.11a
0.05a
* SP = Storage period in days
Means in the same column bearing different superscript letters are significantly
different (p < 0.05).
n=3
Table (7): The effect of storage period at room temp. on the
proximate composition of natural orange juice.
*SP
Moisture
(%)
Fiber
(%)
CHO
(%)
Protein
(%)
Oil
(%)
Ash
(%)
0
89.63a
0.06a
10.04a
0.11a
0.12a
0.05a
3
90.00a
0.06a
9.68b
0.10a
0.11a
0.06a
* SP = Storage period in days
Means in the same column bearing different superscript letters are significantly
different (p < 0.05).
n=3
53
4.2.3. Titratable Acidity
The Titratable acidity for the orange juice was 1.33 mg/100 g at the
beginning of storage. The Titratable acidity was significantly different
(p ≤ 0.05) but in all cases it was within the recommended values (0.6 to
1.6 mg/100 g) reported by Redd et al., (1986). With storage, a significant
increase in acidity (p ≤ 0.05) was observed in orange juice at refrigerated
temperature (Table8) and at room temperature (Table9), after 3 days. This
increase may be due to the start of spoilage or fermentation of the sample.
4.2.4. Total soluble solids
The Total soluble solids content of fresh orange juice (Table8) did not
show significant changes (p ≥0.05) during storage at refrigerator for 3
days. But orange juice stored at room temperature (Table9) showed a
slight decrease in total soluble solids content at the end of storage period
(3days), which could be due to microbial growth.
4.2.5. Ascorbic acid
Ascorbic acid results have shown significant changes during storage
period at refrigerated and room temperature for orange juice. Initially
ascorbic acid content of the orange juice was 49.95 mg/100 ml. Ascorbic
acid
for
refrigerated
orange
juice
decreased
(p ≤ 0.05)
from
49.95mg/100ml to 36.5mg/100ml (Table 8) after 3 days of storage.
Similarly ascorbic acid for orange juice stored at room temperature
(Table9) for the same period decreased (p ≤ 0.05) by 28.5% from its initial
value. Apparently the loss in ascorbic acid for orange juice stored at room
temperature was slightly higher than that stored at refrigerated
temperature.
54
Table (8): The effect of storage period at refrigeration temp. on the pH,
Acidity, TSS, Ascorbic acid of natural orange juice.
pH
T.A.
(%)
T.S.S.
(%)
A.A.
(mg/100ml)
0
4.00a
1.33b
10.55a
49.95a
3
3.87b
1.56a
10.60a
36.50b
*SP
*SP= Storage period in days. TA= titratable acidity; TSS =total soluble solids;
A.A. =Ascorbic acid.
Means in the same column bearing different superscript letters are significantly
different (p < 0.05).
n=3
Table (9): The effect of storage period at room temp. on the pH,
Acidity, TSS, Ascorbic acid of natural orange juice.
pH
T.A.
(%)
T.S.S.
(%)
A.A.
(mg/100ml)
0
4.00a
1.33b
10.55a
49.95a
3
3.20b
1.6a
10.40b
35.70b
*SP
*SP= Storage period in days. TA= titratable acidity; TSS =total soluble solids;
A.A. = Ascorbic acid
Means in the same column bearing different superscript letters are significantly
different (p < 0.05).
n=3
55
4.2.6. Minerals
At the beginning of storage the minerals content for fresh orange juice
were, potassium (K) 1.45mg/L, sodium (Na) 1.35mg/L, calcium (Ca) 27.5
mg/L and magnesium (Mg) 10.35 mg/L (table 3). At the end of
refrigerated storage (3 day), none of the minerals tested i.e. Na, K, Ca and
Mg have shown any change (Table 10).
However the orange juice stored at room temperature (Table11)
experienced slight significant decrease (p ≤0.05) in potassium and
magnesium contents at the end of storage (3days). Calcium and sodium
contents practically did not alter throughout storage, regardless of the
temperature conditions used.
4.2.7. Sensory evaluation
Table 12 shows the effects of storage period and temperature condition
on the sensory properties of orange juice.
The storage of orange Juice indicated greatest degradation of colour at
each of the two temperatures. The visual colour scores of orange juice
stored at refrigerated temperature had significantly higher scores than that
stored at room temperature for the same storage period (3days). This
indicates that panelists prefer the color of refrigerated orange juice. Within
each temperature conditions the visual colour of orange juice is affected
by the storage period. The aroma and overall acceptability scores of
orange juice stored at refrigerated temperature had significantly higher
scores than the aroma and overall acceptability scores of orange juice
stored at room
56
Table (10): The effect of storage period at refrigeration temp. on the
minerals K, Na, Ca, Mg of natural orange juice.
*SP
K (mg/L)
Na (mg/L)
Ca (mg/L)
Mg (mg/L)
0
1.45a
1.35a
27.50a
10.35a
3
1.45a
1.30a
27.50a
10.35a
SP = Storage period in days
Means in the same column bearing different superscript letters are significantly
different (p < 0.05).
n=3
Table (11): The effect of storage period at room temp. on the minerals
K, Na, Ca, Mg of freshly orange juice.
*SP
K (mg/L)
Na (mg/L)
Ca (mg/L)
Mg (mg/L)
0
1.45a
1.35a
27.50a
10.35a
3
1.35b
1.30a
27.45a
10.25b
SP = Storage period in days
Means in the same column bearing different superscript letters are significantly
different (p < 0.05).
n=3
57
temperature for the same storage period (3days). That means the panelists
prefer the aroma and overall acceptability of refrigerated orange juice.
Sensory evaluation of stored orange juice revealed that refrigerated
orange juice had significantly higher taste scores than that stored at room
temperature for the same storage period (3days).
58
Table (12): The effect of storage period and temperature on sensory
evaluation of fresh orange juice stored for 3 days
*SP
Temp.
0
Colour
Aroma
Taste
Overall
acceptability
4.40a
4.70a
4.60a
4.70a
3
1
3.50b
2.80b
2.30b
1.80b
3
2
3.40b
1.80c
1.90c
1.60c
*SP= Storage period in days. 1= refrigerated temp. 2= room temp.
Means in the same column bearing different superscript letters are significantly different
(p < 0.05).
n=3
59
CONCLUSION
Natural orange drink had a good amount of vitamin C; and consequently
it is considered as very good source of vitamin C.
Storage at room temperature or under refrigeration had a minimal effect
on the proximate composition of natural orange juice and drink .however
both resulted in substantial reduction in ascorbic acid of natural orange
juice and drink.
Titratabl acidity increased gradually throughout the period of storage.
Sensory evaluation revealed that colour of both natural orange juice and
drink darkened upon storage at room temperature.
Variations in the characteristics with storage time were always more
marked at room temperature conditions.
RECOMMENDATIONS
Orange juice should be stored at low temperature after packaging to
minimize the deterioration of quality.
Orange juice should be distributed in refrigerated trucks throughout
distribution channels.
Regular consumption of natural fruit drinks and juices especially orange
juice because it is considered as very good source for vitamin C.
60
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