Physico-chemical Properties of Tree Locust Flour as
Influence by pH and/or NaCl Concentration
By
Khalid Ayoub Hassan Magzoub
B.Sc (Agric.) honours
Faculty of Agriculture - University of Khartoum
September 2001
A Dissertation
Submitted to the University of Khartoum in partial fulfillment of the
requirements of the degree of M.Sc. in Food Science and Technology
Supervisor
Professor. Elfadil Elfadl Babiker
Department of Food Science and Technology
Faculty of agriculture – University of Khartoum
June 2006
Dedication
To my Family,
Friends
and colleagues
with love
Acknowledgements
I would like to express my deepest thanks to my supervisor Dr. Elfadil E.
Babiker for his close supervision, Personal gaudiness and fruitful criticism
throughout the course study. My deep gratitude and sincere thanks are due to Dr.
Gammaa A. Osman and Ustaz, Amro B. Hassan, National Center for Research for
their continuous interest valuable discussion and useful suggestions. My thanks
are extended to Mr. Hago E. Elhassan, National Center for Research for his
unlimited help and valuable assistant.
My deep gratitude to all staff, of the Department of food Science and
Technology, Faculty of Agriculture, University of Khartoum, For their continuous
help and encouragement.
Lastly, but no mean the last, my thanks are due to my family, friends and
colleagues, who were ready to render any assistance I ask for to complete this
work.
Abstract
The aim of this study was to investigate the chemical composition of
boiled and fried tree locust flour and its functional properties as affected
by pH and sodium chloride concentration. Emulsifying activity,
emulsification capacity, emulsion stability, foaming capacity, foam
stability, protein solubility, least gelation were determined under different
sodium chloride concentrations and pH values for both boiled and fried
tree locust flour. The water and fat absorption capacity as well as
wettabillity, dispersibility and bulk density of both boiled and fried tree
locust flour were also determined.
Proximate composition results showed that both boiled and fried tree
locust contained high levels of protein (66.24%, 67.75%), ash (5.53%,
6.017%), moisture (7.47%, 5.467%) and fiber and (8.377%,7.317%).
The results indicated that the emulsion capacity and protein solubility
were increased, while the emulsification activity and emulsification
stability were decreased, for boiled sample, as NaCl concentration was
increased. However, no consistent change was observed in foaming
capacity, while no change for foaming stability.
For fried samples,
emulsification activity, emulsification capacity, emulsification stability,
foaming capacity and protein solubility were improved with addition of
NaCl salt. The results also showed that no gel was formed for fried
samples, while weak gel was observed at 6, 8, and 10%, for boiled
samples.
For the effect of pH, the results indicated that, emulsifying activity,
emulsification capacity and foaming capacity were affected by pH, for
both boiled and fried samples, with higher values at alkaline region, and
lower values at acidic range except for foaming capacity. However, the
emulsification stability for both samples was of no regular pattern of
change at both acidic and alkaline region. Moreover, pH had no effect in
least gelation concentration except at 10%. Results showed that frying
increased bulk density and fat absorption capacity and decreased water
absorption capacity, dispersibility of boiled samples was lower at neutral
pH with remarkable increase on either sides of pH, while no change was
observed for fried sample.
‫ﻣﻠﺨﺺ ﺍﻷﻃﺮﻭﺣﺔ‬
‫ه ﺪف ه ﺬا اﻟﺒﺤ ﺚ اﻟ ﻰ دراﺳ ﺔ اﻟﺨ ﺼﺎﺋﺺ اﻟﻮﻇﻴﻔﻴ ﺔ ﻟﻤ ﺴﺤﻮق اﻟﺠ ﺮاد اﻟﻤ ﺴﻠﻮق واﻟﻤﺤﻤ ﺮ ﺣ ﺴﺐ‬
‫ﺗﺄﺛﺮهﺎ ﺑﺎﻟﺮﻗﻢ اﻟﻬﻴﺪروﺟﻴﻨﻲ وﺗﺮآﻴﺰ ﻣﻠﺢ آﻠﻮرﻳﺪ اﻟ ﺼﻮدﻳﻮم‪ .‬ﺗ ﻢ ﺗﻘ ﺪﻳﺮ آ ﻞ ﻣ ﻦ اﻟﻨ ﺸﺎط اﻹﺳ ﺘﺤﻼﺑﻲ‬
‫اﻟ ﺴﻌﺔ اﻹﺳ ﺘﺤﻼﺑﻴﺔ‪ ،‬اﻟﺜﺒ ﺎت اﻹﺳ ﺘﺤﻼﺑﻲ‪ ،‬اﻟ ﺴﻌﺔ اﻟﺮﻏﻮﻳ ﺔ‪ ،‬اﻟﺜﺒ ﺎت اﻟﺮﻏ ﻮي وذوﺑﺎﻧﻴ ﺔ اﻟﺒ ﺮوﺗﻴﻦ‬
‫ﻟﻤﺴﺤﻮق اﻟﺠﺮاد ﺑﻨﻮﻋﻴﻪ ﻟﻌﺪة ﻗﻴﻢ ﻣﻦ اﻟﺮﻗﻢ اﻟﻬﻴﺪروﺟﻴﻨﻲ وﻋﺪة ﺗﺮاآﻴﺰ ﻟﻤﺤﻠﻮل آﻠﻮرﻳ ﺪ اﻟ ﺼﻮدﻳﻮم‪.‬‬
‫آﺬﻟﻚ ﺗﻢ ﺗﻘ ﺪﻳﺮ آ ﻞ ﻣ ﻦ ﺳ ﻌﺔ أﻣﺘ ﺼﺎص اﻟﻤ ﺎء واﻟﺰﻳ ﺖ و اﻟﺘﺮﻃﻴ ﺐ واﻹﻧﺘ ﺸﺎرﻳﺔ ﻟﻜ ﻼ اﻟﻨ ﻮﻋﻴﻦ ﻣ ﻦ‬
‫ﻣﺴﺤﻮق اﻟﺠﺮاد‪.‬‬
‫أوﺿ ﺤﺖ ﻧﺘ ﺎﺋﺞ اﻟﺘﺤﻠﻴ ﻞ اﻟﺘﻘﺮﻳﺒ ﻲ أن آ ﻼ اﻟﻌﻴﻨﺘ ﻴﻦ ﻣ ﻦ ﻣ ﺴﺤﻮق ﺟ ﺮاد ﺳ ﺎري اﻟﻠﻴ ﻞ اﻟﻤ ﺴﻠﻮق‬
‫واﻟﻤﺤﻤ ﺮ ﺗﺤﺘﻮﻳ ﺎن ﻋﻠ ﻲ ﻣ ﺴﺘﻮﻳﺎت ﻋﺎﻟﻴ ﺔ ﻣ ﻦ اﻟﺒ ﺮوﺗﻴﻦ )‪ .( 66.24%, 67.75%‬ﺑﺎﻹﺿ ﺎﻓﺔ أﻟ ﻰ‬
‫اﻟﺮﻣﺎد )‪ ،(5.53%, 6.017%‬اﻟﺮﻃﻮﺑﺔ )‪ ،(7.47%, 5.467%‬واﻷﻟﻴﺎف )‪.(8.377 7.317%‬‬
‫آﺬﻟﻚ ﻓﻘﺪ اﺷﺎرت اﻟﻨﺘﺎﺋﺞ ان اﻟﺴﻌﺔ اﻹﺳﺘﺤﻼﺑﻴﺔ وذوﺑﺎﻧﻴﺔ اﻟﺒ ﺮوﺗﻴﻦ ﺗﺰﻳ ﺪ ﺑﺰﻳ ﺎدة ﺗﺮآﻴ ﺰ ﻣﻠ ﺢ آﻠﻮرﻳ ﺪ‬
‫اﻟﺼﻮدﻳﻮم‪ ،‬ﺑﻴﻨﻤﺎ ﻳﻘﻞ اﻟﻨﺸﺎط اﻹﺳﺘﺤﻼﺑﻲ واﻟﺜﺒﺎﺗﻴﺔ اﻹﺳﺘﺤﻼﺑﻴﺔ ﻟﻠﻌﻴﻨ ﺎت اﻟﻤ ﺴﻠﻮﻗﺔ‪ .‬أﻣ ﺎ ﻓﻴﻤ ﺎ ﻳﺨ ﺺ‬
‫اﻟﺨﺎﺻﻴﺔ اﻟﺮﻏﻮﻳﺔ ﻓﺈﻧﻪ ﻻﻳﻮﺟﺪ ﺗﻐﻴﻴﺮ ﻓ ﻲ اﻟﺜﺒﺎﺗﻴ ﺔ اﻟﺮﻏﻮﻳ ﺔ ‪ ،‬ﺑﻴﻨﻤ ﺎ آ ﺎن اﻟﺘﻐﻴﻴ ﺮ ﻗ ﻲ اﻟ ﺴﻌﺔ اﻟﺮﻏﻮﻳ ﺔ‬
‫ﻏﻴ ﺮ ﺛﺎﺑ ﺖ‪ .‬ﺑﺎﻟﻨ ﺴﺒﺔ ﻟﻠﻌﻴﻨ ﺎت اﻟﻤﺤﻤ ﺮة ‪ ،‬ﻓ ﺈن اﻟﻨ ﺸﺎط اﻹﺳ ﺘﺤﻼﺑﻲ ‪،‬اﻟ ﺴﻌﺔ اﻹﺳ ﺘﺤﻼﺑﻴﺔ‪ ،‬اﻟﺜﺒﺎﺗﻴ ﺔ‬
‫اﻹﺳﺘﺤﻼﺑﻴﺔ‪ ،‬اﻟﺴﻌﺔ اﻟﺮﻏﻮﻳﺔ وذوﺑﺎﻧﻴﺔ اﻟﺒ ﺮوﺗﻴﻦ ﺗﺘﺤ ﺴﻦ ﻣ ﻊ إﺿ ﺎﻓﺔ ﻣﻠ ﺢ آﻠﻮرﻳ ﺪ اﻟ ﺼﻮدﻳﻮم‪ .‬آ ﺬﻟﻚ‬
‫أوﺿ ﺤﺖ اﻟﻨﺘ ﺎﺋﺞ ﻋ ﺪم ﺗﻜ ﻮن ه ﻼم ﻓ ﻲ اﻟﻌﻴﻨ ﺎت اﻟﻤﺤﻤ ﺮة ‪ ،‬ﺑﻴﻨﻤ ﺎ آ ﺎن ﺗﻜﻮﻧ ﻪ ﺿ ﻌﻴﻔًﺎ ﻓ ﻲ اﻟﻌﻴﻨ ﺎت‬
‫اﻟﻤﺴﻠﻮﻗﺔ‪.‬‬
‫أﻇﻬ ﺮت اﻟﻨﺘ ﺎﺋﺞ أن اﻟﻨ ﺸﺎط اﻹﺳ ﺘﺤﻼﺑﻲ ‪ ،‬اﻟ ﺴﻌﺔ اﻹﺳ ﺘﺤﻼﺑﻴﺔ واﻟ ﺴﻌﺔ اﻟﺮﻏﻮﻳ ﺔ ﺗﺘ ﺄﺛﺮ ﺑ ﺎﻷس‬
‫اﻟﻬﻴﺪروﺟﻴﻨﻲ ﺑﻘﻴﻢ ﻋﻠﻴﺎ ﻓﻲ اﻟﻤﺪي اﻟﻘﻠﻮي ودﻧﻴﺎ ﻓﻲ اﻟﻤﺪي اﻟﺤﻤﻀﻲ ﻓﻴﻤﺎ ﻋ ﺪا اﻟ ﺴﻌﺔ اﻟﺮﻏﻮﻳ ﺔ‪ .‬ﺑﻴﻨﻤ ﺎ‬
‫ﻧﺠﺪ أن اﻟﺜﺒﺎﺗﻴﺔ اﻹﺳ ﺘﺤﻼﺑﻴﺔ ﻟﻜﻠﺘ ﺎ اﻟﻌﻴﻨﺘ ﻴﻦ ﺗﺘﻐﻴ ﺮ ﺑ ﻨﻤﻂ ﻏﻴ ﺮ ﻣﻨ ﺘﻈﻢ ﻓ ﻲ اﻟﻤ ﺪي اﻟﻘﻠ ﻮي واﻟﺤﻤ ﻀﻲ‪.‬‬
‫ﺑﺎﻹﺿﺎﻓﺔ اﻟﻰ ذﻟ ﻚ ﻓﻘ ﺪ أﻇﻬ ﺮت اﻟﻨﺘ ﺎﺋﺞ أن درﺟ ﺔ اﻷس اﻟﻬﺎﻳ ﺪروﺟﻴﻨﻲ ﻻﺗ ﺆﺛﺮ ﻓ ﻲ ﺗﻜ ﻮﻳﻦ اﻟﻬ ﻼم ‪،‬‬
‫ﺑﺈﺳﺘﺜﻨﺎء اﻟﺘﺮآﻴﺰ ‪.10%‬‬
‫آﺬﻟﻚ أﻇﻬﺮت اﻟﻨﺘﺎﺋﺞ أن ﻋﻤﻠﻴ ﺔ اﻟﺘﺤﻤﻴ ﺮ ﺗﺰﻳ ﺪ ﻣ ﻦ اﻟﻜﺜﺎﻓ ﺔ اﻟﻜﻠﻴ ﺔ وﺳ ﻌﺔ إﻣﺘ ﺼﺎص اﻟ ﺪهﻮن‪ ،‬وﺗﻘﻠ ﻞ‬
‫ﻣﻦ ﺳﻌﺔ إﻣﺘﺼﺎص اﻟﻤﺎء‪ .‬آﺬﻟﻚ إن ﺧﺎﺻﻴﺔ اﻹﻧﺘﺸﺎرﻳﺔ ﺑﺎﻟﻨﺴﺒﺔ ﻟﻠﻌﻴﻨﺎت اﻟﻤ ﺴﻠﻮﻗﺔ آﺎﻧ ﺖ ﻣﺘﺪﻧﻴ ﺔ ﻋﻨ ﺪ‬
‫درﺟﺔ اﻷس اﻟﻬﻴﺪروﺟﻴﻨﻲ اﻟﻤﺤﺎﻳﺪ ‪ ،‬ﻣﻊ زﻳﺎدة واﺿﺤﺔ ﻓ ﻲ آ ﻼ ﻃﺮﻓ ﻲ اﻷس اﻟﻬﺎﻳ ﺪروﺟﻴﻨﻲ‪ ،‬ﺑﻴﻨﻤ ﺎ‬
‫ﻟﻢ ﻳﻼﺣﻆ أي ﺗﻐﻴﻴﺮ ﺑﺎﻟﻨﺴﺒﺔ ﻟﻠﻌﻴﻨﺎت اﻟﻤﺤﻤﺮة‪.‬‬
Table of Contents
Dedication ………………………………………………………….
Acknowledgements ………………………………………………
Abstract …………………………………………………………….
Arabic abstract ……………………………………………………..
Table of Contents ………………………………………………….
List of Tables ………………………………………………………
Chapter one Introduction ………………………………………..
Chapter two Literature Review………………………………….
2.1. Nutritive value of Insects …………………………………….
2.2. Chemical composition of insects:…………………………….
page
ii
iii
iv
vi
vii
x
1
3
3
3
2.3. Functional properties of protein ……………………………… 5
2.4. Protein solubility……………………………………………… 6
2.5.Fat absorption capacity ………………………………………. 7
2.6.Bulk Density ………………………………………………….. 8
2.7. Gelation ………………………………………………………. 8
2.8. Foaming properties …………………………………………… 9
2.9. Emulsification properties ……………………………………..
10
2.10. Wettability……………………………………………………
11
2.11. Dispersibility ………………………………………………..
11
2.12.Water Retention Capacity
Chapter Three :Materials And Methods…………………….
3.1 Materials ………………………………...............................
3.2 Methods ………………………………………....................
3.2.1 Samples preparations ……………………………………..
3.2.2 Protein Content …………………………………………….
11
13
13
13
13
13
3.2.3 Determination of nitrogen solubility at various pH
13
values……...
3.2.4 Determination of nitrogen solubility at different NaCl
14
solutions
3.2.5 Functional properties:……………………………………..
15
3.2.5.1 Water retention capacity (WRC) ………………………..
3.2.5.2 Fat absorption capacity (FAC)……………………………
3.2.5.3 Bulk density (BD)………………………………………..
3.2.6 Emulsification properties ………………………………….
3.2.6.1 Emulsification capacity (EC): …………………………..
3.2.6.2Emulsificationa activity (EA) and emulsion stability (ES).
page
15
15
15
16
16
3.2.7 Foaming properties…………………………………………
3.2.7.1 Foaming capacity (FC):………………………………….
16
17
17
3.2.7.2 Foam stability (FS): ……………………………………..
17
3.2.8 Gelation:……………………………..……………………..
18
3.2.9 Dispersibility: ……………………………………...........
18
18
20
3.2.10 Wettability …………………………………….................
Chapter (4): Results and Discussion
4.1. Proximate composition of boiled and fried tree locust
20
4.2. Effect of NaCl Concentration on emulsification activity (EA)
of boiled and fried tree locust flour:
22
43. Effect of NaCl Concentration on emulsification capacity (EC)
of boiled and fried tree locust flour:
22
4.4. Effect of NaCl Concentration on emulsification stability (ES)
of boiled and fried tree locust flour:
25
4.5. Effect of NaCl Concentration on foaming capacity (FC) of
boiled and fried tree locust flour:
27
4.6. Effect of NaCl Concentration on foaming stability (FS) of
boiled and fried tree locust flour:
27
4.7. Effect of NaCl Concentration on protein solubility (PS) of
boiled and fried tree locust flour:
31
4.8. Effect of pH on emulsification activity (EA) of boiled and
fried tree locust flour:
33
page
4.9. Effect of pH on emulsification capacity (EC) of boiled and
fried tree locust flour:
33
4.10. Effect of pH on emulsification stability (ES) of boiled and
fried tree locust flour:
36
…………...
4.11. Effect of pH on foaming capacity (FC) of boiled and fried
tree locust flour:
36
4.12. Effect of pH on foaming stability (FS) of boiled and fried
tree locust flour:
39
4.13. Effect of pH on protein solubility of boiled and fried tree
locust flour:
39
4.14. Effect of NaCl concentration on the least gelation
concentration of boiled and fried tree locust flour:
43
4.15. Effect of the pH on the least gelation concentration of boiled
and fried tree locust flour:
4.16. Effect of pH on dispersibiltyy (%) of boiled and fried tree
locust flour:
43
43
4.17. Water and Fat absorption capacity (WAC/FAC) of boiled
and fried tree locust:
48
4.18. Bulk density (BD) of boiled and fried tree locust:
48
4.19 wettability of boiled and fried tree locust:
Chapter (5): Conclusions and recommendations
5.1. Conclusions
5.2. Recommendations
49
50
50
50
References
52
List of Tables
page
Table (1): Chemical composition of boiled and fried locust
Table (2): Emulsification activity (EA) of boiled and fried tree Locust
flour at different NaCl concentrations
21
23
Table (3): Emulsification capacity (EC) of boiled and fried tree
Locust flour at different pH values
24
Table (4): Emulsification stability (ES) of boiled and fried tree
locust at different NaCl concentrations
26
Table (5): Foaming capacity (FC) of boiled and fried tree locust at
different NaCl concentrations
Table (6a): Effect of NaCl concentration on foam stability (%) of
boiled tree locust flour
28
29
Table (6b): Effect of NaCl concentration on foam stability (%) of fried
tree locust flour
30
Table (7): Protein solubility (PS) of boiled and fried tree locust at
different NaCl concentration
32
Table (8): Emulsification activity (EA) of boiled and fried tree
locust at different pH values
34
Table (9): Emulsification capacity (EC) of boiled and fried tree
Locust flour at different pH values
Table (10): Emulsification stability (ES) of boiled and fried tree
35
37
page
locust at different pH values
Table (11): Foaming capacity (FC) of boiled and fried tree locust at
different pH values
Table (12a): Effect of pH on foam stability (%) of boiled tree locust
flour
Table (12b): Effect of pH on foam stability (%) of fried tree locust
flour
38
40
41
Table (13): Protein solubility (PS) of boiled and fried tree locust at
different pH values
42
Table (14a): Effect of NaCl concentration on the least gelation
concentration of boiled tree locust flour
44
Table (14b): Effect of NaCl concentration on the least gelation
concentration of fried tree locust flour
45
Table (15a): Effect of pH concentration on the least gelation
concentration of boiled tree locust flour
46
Table (15b): Effect of pH concentration on the least gelation
concentration of fried tree locust flour
Table (16): Effect of pH on dispersibiltyy (%) of boiled and fried tree
46
47
Table (17): Fat and water absorption capacity and bulkdensity
properties of boiled and fried tree locust flour
47
CHAPTER ONE
INTRODUCTION
Insects constitute more than half of the known species of animal (Stork,
1991). About one million species have been named and classified and
several thousand more are discovered each year (Vines and Rees, 1972) and
that about 70% of all known species of animal are insects. Although there is
many land animals and are widely spread, they adapt to all types of
environment. Their ubiquity, small size, amazing range of adaptation and
their fecundity, all make them man’s most serious rivals for the possession
of the earth. Among the invertebrates, insects are the only group that can fly
and feed on plant material, while some feed on animals’ tissue and wastes
(Florence, 1996). It is hardly possible to over -emphasize the importance of
insects. Some insect like butterflies, bees and some sap sucking once bring
direct benefit to man pollinator of flower; some are predators on pest and as
objects of beauty. Others are destructive to cloths, furniture, book and
buildings for example ant and termites.
The notable destructive group species to forestry are the larvae of
lepidoptera (caterpillars), grasshoppers, locusts and termites. They defoliate
the leaves of wilding poles, seedling, herb and shrubs that are suppose to
regenerate the logged over forest. Although, man suffers and benefits from
the insects legions (Vines and Rees, 1972) noted that on the whole the
suffering outweighs the benefits. It was further observed that pollination is
by far the most useful activity that insects carryout from his contribution.
The most important crop pollinators are although visitors to flowers also
include small beetles and a variety of flies. Indirectly, insects also help man
in other ways, predator insects, such as a wasps and ladybugs, attack harmful
pest although those pest are often insects themselves.
Insects have played
an important role in the history of human nutrition. In Africa, Asia and Latin
America (Duffey, 1980). Aletor (1995) noted that Anaphae venata is a good
source of protein in human diet since it averagely contains about
22.1/
100g of protein and Ashiru (1988) reported a calorific value of 61 1k cal
(2266 kj) 100g for the caterpillar of Anaphae venata. Other beneficial insects
live on organic remains, helping to recycle nutrients that plants can then use.
These recycles include minute insects, such as springtails and a variety of
heavily built beetles. Some of these beetles bury the carcasses of small bird
and mammals, slowly away the ground until the corpse sinks – below the
surface. It is, however, not strange the people travel 200 – 300 km to pick
caterpillar and trader come from Lusaka and the copper belt (990km). He
further noted that in several area of Zimbabwe. Some families make a fairly
good living from selling caterpillars. Insect are not only widely in the village
market of developing world but many make their way to urban markets and
restaurants.
Some of the selected dominant insect species are pests of some of economic
timber tree species such as Anaphe venata which browses on the leaf of
Triplochiton scleroxylon. Termites consume most of all available tree
species as well as tree hopper Meal bug is the pest of Cola gigantia fruit, Ant
chew through most tree species for their shelter. Grasshopper and cricket eat
most of tree species mostly when they are in seedling state. In this study, we
would like to investigate the effect of boiling and frying on protein solubility
and functional properties of tree locust flour as a function of NaCl
concentrations (M) and pH to predict the possibility to utilize locust flours in
the food industry.
CHAPTER TWO
LITERATURE REVIEW
2.1 Nutritive value of Insects:
Insects are the most successful group of animals constituting about 76%
of known species of animals (Yoloye, 1988). Insects affect man either as
destroyers of man’s valuable materials and crops or as sources of his
nutrients. Goodman (1989) reported that chitin, an important insect
component, can significantly reduce serum cholesterol, and serve as a
haemostatic agent for tissue repairs and for accelerating healing of burns
and wound. The cultural practice of entomophagy is an old and wellestablished custom in non-industrialized regions of the world (Sutton,
1988). The high cost of animal protein, which is beyond the reach of the
poor has greatly encouraged entomophagy. Insects are valuable sources
of animal protein for Zambia’s rural population since meat from
domesticated and wild animals are scarce (Mwizenge, 1993). A 10%
increase in the world supply of animal proteins through mass production
of insects can largely eliminate the malnutrition problem and also
decrease the pressure on other protein sources (Robert, 1989). Studies in
Nigeria have shown that entomophagy has contributed significantly to the
reduction in protein deficiencies in the country (Ashiru, 1988, Fasoranti
and Ajiboye, 1993).
2.2. Chemical composition of insects:
McHargue (1917) conducted proximate and amino acid analyses on two
species of insects, one of which was the June bug, Lachnosterna sp.
(Family Scarabaeidae) (Phyllophaga
Lachnosterna). Analysis showed
"such a large percentage of protein present in the dry state," that further
studies were conducted, but McHargue doesn't give the percentage found.
Data are presented on the amino acid content in comparison to beef roast
and turkey white meat. Lachnosterna was equivalent to the meats in lysine
(8.02% of analyzed nitrogen), slightly lower in arginine (11.53%) and
cystine (0.35%) and had only about 50% as much histidine content
(6.57%). He also stated that grasshoppers, they might afford a new highprotein source He conducted a proximate analysis on dried Melanoplus spp.
(Acrididae) showing 75.3% protein, 7.21% fat, and 5.61% ash. Amino acid
analysis showed the grasshoppers to be high in lysine compared to other
sources. Minerals were also analyzed.
Landry et al (1986) provided proximate and amino acid analyses on larvae
of six species in three families: Family Noctuidae included the armyworm,
Pseudaletia unipuncta (Haworth), the southern armyworm, Spodoptera
eridania (Cramer), and the fall armyworm, Spodoptera frugiperda (J.E.
Smith); Family Saturniidae included Callosamia promethea (Drury) and
Hyalophora cecropia (L.); and the Family Sphingidae included Manduca
sexta (L.). The noctuid larvae ranged between 54% and 58% crude protein
on a dry weight basis. The fat, and thus energy content was higher in the
larvae than in conventional protein supplements. The extremely high fat
content in S. frugiperda, however, which were fed on an artifical diet,
probably reflects the diet and the fact that not all larvae were able to clear
the gut before they were harvested. In the saturniids, crude protein was
49.4% in C. promethea and 54.7% in H. cecropia. Fat content was similar
to that found in fish and meat supplements.
The sphingid, M. sexta,
contained 58% crude protein and a very high fat content whether reared on
artificial diet or on fresh plant material.
DeFoliart (1991) reviewed the available data on insect fatty acids and
reports that the proportions of saturated/unsaturated fatty acids are less than
40% saturated in most edible insects, grouping them with poultry and fish.
Another notable feature of insect fatty acids is the very high ratio of the
polyunsaturates, linoleic and linolenic acids, higher in general than found in
poultry and fish.Studier and Sevick (1992) reported the live and dry mass,
water content, nitrogen, sodium, potassium, magnesium, calcium and total
iron concentrations for representatives (mostly adults) of 16 orders of
insects (360 species) occurring in south-central Michigan.The authors
report that, compared to published nutritional requirements (when meeting
caloric requirements) for growth and reproduction in birds and mammals,
insects are excellent sources of nitrogen, potassium and magnesium, highly
variable sources of sodium and iron, and, rarely, adequate calcium sources.
2.3. Functional properties:
Functionality of food proteins is defined as those physical and chemical
properties, which affect the behavior of proteins in food systems during
processing, storage, preparation and consumption (Fennema, 1996). A
functional property is any nonnutritional property of a food or food
additive that affects its utilization (Rhee, 1985). Many factors influence
the functional properties of proteins, including moisture, temperature, pH,
concentration, reaction time, enzymes, chemical additives, mechanical
processing, ionic strength, and amount, sequence, rate, and time of the
additives (Johnson, 1970).
The range of desirable and attractive
functional properties that should be looked for is almost as board as the
range of foods themselves. For example, if one is considering producing
a beverage, two desirable functional properties should be considered
solubility and suitable viscosity. For bread, the need is for a protein that
is compatible with gluten. For various meat systems, desirable qualities
would include water-binding, emulsifying properties and the ability to be
formed into fibers. For other purposes, the properties of gel formation,
whippability, adhesiveness and thickenening might be considered
beneficial (Mattil, 1971).
2.4. Protein solubility:
For proteins and high protein foods used as functional ingredients,
nitrogen solubility is one of the useful parameters for predicting waterlipid-protein interactions (Mattil, 1971 & Kinsella, 1976). Thus, the
amount of soluble protein can often be correlated with the amount of fat
that can be emulsified or the amount of foam produced (Okaka & Potter,
1979). The solubility of the protein is the thermodynamic manifestation
of the equilibrium between protein-protein and protein solvent
interactions. The major interactions that influence the solubility
characteristics of proteins are hydrophobic and ionic in nature.
Hydrophobic interactions promote protein-protein interactions and result
in decreased. Whereas ionic interactions promote protein-water
interactions and result in increased solubility (Fennema, 1996). Nitrogen
solubility is influenced by several solution conditions, such as pH, ionic
strength, temperature, and the presence of organic solvents (Fennema,
1996).
Also nitrogen solubility profiles are affected by varietals
differences (Conkerton and Ory, 1976), degree of heat treatment, growing
location and storage conditions (Cherry, 1975).
Nitrogen solubility profiles over a range pH values are being used
increasingly as a guide for protein functionality, since this property often
correlates with important properties such as emulsification and foaming
capacity (Sosulski et al, 1987). Omotoso (2006) reported that the protein
solubility of Cirina forda is lower in acid media. Higher solubility values
were obtained in alkaline media and the isoelectric points (IEP) values
are 4, 6 and 9. The high pH solubility of C. forda protein in alkaline
media indicated that it might be useful in the formulation of food like
meat products. The solubility of protein depends on hydration and the
degree of hydrophobicity of the protein molecules (Sathe and Salunkhe,
1981).
2.5. Fat absorption capacity:
The ability of protein to bind fat is an important functional property for
food applications such as meat replacers and extenders, principally
because it enhances flavour retention and reputedly improves mouth feel
(Kinsella, 1976).
The key role of fat in food flavouring had been
demonstrated by kinsella (1975) and its capacity to improve flavour
carry-over in simulated foods during processing is apparent (Wolf and
Gowan, 1975).
Oil absorption is mainly attributed to the physical
entrapment of oil and is related to the number of nonpolar side chains on
proteins that bind hydrocarbon chains of fats (Kinsella, 1979 & Lin et al,
1974).
Fat absorption is usually measured by adding excess liquid fat
(oil) to a protein powder, thoroughly mixed and centrifuged. Thereafter,
the amount of bound or absorbed oil will be determined (Lin et al, 1974
& Wang & Kinsella, 1976)a. The amount of oil, protein sample, kind of
oil, holding and centrifuging conditions and units of expression have
varied slightly from one investigato another (Hutton and Campbell,
1981). The mechanism of fat absorption is not clear. However Wang
and Kinsella (1976)a have attributed fat absorption mostly to physical
entrapment of oil.
Factors affecting protein-lipid interaction include
protein conformation, protein-protein interactions, and the spatial
arrangement of the lipid phase resulting from the lipid-lipid interaction
(Hutton and Campbell, 1981). Noncovalent bonds, such as hydrophobic,
electrostatic, and hydrogen, are the forces involved in the protein-lipid
intractions.
Hydrogen bonding is of secondary importance in lipid
protein complexes, although it is indirectly important in hydrophobic
bonding (Karel, 1973), since in aqueous media the water-water by
hydrogen bonding is much stronger than interaction between water and
nonpolar groups, thus giving rise to hydrophophilic bonding between
water and nonpolar groups, electrostatic attraction can occur between the
negatively charged phosphate groups of phospholipids and positively
charged protein groups (such as lysyl or guanidyl) or between a positively
charged group in the phospholipids (e.g.choline) and a negatively charged
amino acid side chain (e.g.aspartyl). A related mode of binding is the
formation of salt bridges between a negatively charged amino acid side
chain and a negatively charged phosphate group of a phospholipids via
divalent bond of calcium or other metal ions (Karel, 1973; Pomeranz,
1973 & Ryan, 1977). Hydrophobic bonding is likely to play a major role
in stabilizing the interactions of both polar and nonpolar lipids with
proteins (Ryan, 1977). However, according to Wall (1979) lipids bind to
proteins mainly through association with hydrophobic groups.
2.6. Bulk Density:
The bulk density depends on interrelated factors including intensity of
attractive interparticle forces, particle size, number of contact points
(Peleg and Bagley, 1983).
It also depends on type of solvent used to
extract the protein products (Wang and Kinsella, 1976)a and on method of
drying (Bryant, 1988). . Higher bulk density is desirable since it helps to
reduce the paste thickness, which is an important factor in convalescent
and child feeding (Padmashree et al, 1987).
2.7. Gelation:
Gelation may be defined as a protein aggregation in which polymerpolymer and polymer solvent interactions as well as attractive and
repulsive forces are so balanced that a tertiary network or matrix is
formed. Such a matrix is capable of immobilizing or trapping large
amounts of water (Schmidt, 1981). Factors that affect gelation properties
include protein concentration, protein components in a complex
foodsystem, nonprotein components, pH, ionic and reducing agents and
heat treatment conditions (Schmidt, 1981). Gelation involves the
formation of a continuous network that exhibits order. Higher protein
concentration may enhance the rate at which such a network is formed
(Deshpande et al, 1982).
2.8. Foaming properties:
Foaming action is a property desirable for whipped toppings, whipped
desserts and frozen desserts (Circle and Smith, 1972).
The foaming
property of a protein refers to its ability to form a thin tenacious film at
gas-liquid interfaces so that large quantities of gas bubbles can be
incorporated and stabilized (Fennema, 1996). In food systems, foams are
often very complex, including several phases such as a mixture of gases,
liquids and multicomponent solutions of water, polymers and surfactants
(Richert, 1979).
The factors that affecting foaming formation and
stability are environmental factors (pH, sugars, lipids and protein
concentration) and molecular properties (Fennema, 1996).
McWatters
and Cherry (1977) observed that protein solubility was more closely
related to the type of foam produced than the increase in volume. The
foaming capacity of a protein refers to the amount of interfacial area that
can be created by the protein (Fennema, 1996). Foam stability refers to
the ability of protein to stabilize against gravitational and mechanical
stresses (Fennema, 1996). Foam stability is important since the usefulness
of whipping agents depends on their ability to maintain the whip as long
as possible (Lin et al, 1974).
Foam stability was determined by
measuring the decrease in volume of foam as a function of time
(Narayana and Narasinga Rao, 1982). Foam stability also decreased as
the time of autoclaving increased. This decrease is mainly due to
denaturation of the proteins, which become less soluble (Rhahma and
Mostafa, 1988). Foam formation and stability are functions of the type of
protein, pH, processing methods, viscosity and surface tention (
Yatsumatsu at al. 1972). The foaming capacity and foaming stability of
Cirina forda were 7.1% and 3.0% respectively as reported by (Omotoso,
2006). Akubor and Chukwu, (1999) reported that foams are used to
improve the texture, consistency and appearance of food.
Heat
processing considerably decreased the foam capacity and stability of
jackfruit flour (Odoemelam, 2005).
2.9. Emulsification properties:
An emulsion is a dispersed system consisting of two immiscible or
sparingly soluble liquids, termed the oil phase and the water phase,
separated by a third component termed an emulsifier which may be solid,
the interphase between the two phases is very large and its integrity is
critical to the stability of the whole system (Friberg and Venable, 1983 &
Tadros ; Vincent, 1983 & Becher, 1983). Emulsification properties play
a significant role in many food systems including meat products, batters
and dough and salad dressings (Betschart et al , 1979). Factors that affect
emulsifying properties are adsorption kinetics, interfacial load, decrease
of interfacial tension, rheology of the interfacial film, and surface
hydrophobicity of the interfacial film (Das and kinsella, 1990). Many
physical and chemical factors are involved in formation, rheology of the
protein emulsions. Efficiency of emulsification varies with the type of
protein, its concentration, pH, ionic strength, and viscosity of the system,
temperature and the method of preparation of emulsion (Saffle, 1968).
Emulsion capacity (EC) is the volume (ml) of oil that can be emulsified
per gram of protein before phase inversion occurs (Fennema, 1996).
Many factors influence the emulsification capacity including equipment
design, rate of oil addition, temperature, pH, protein type, solubility and
concentration, kind of oil used, salt (type and concentration), sugars and
water content (Saffle, 1968 & Kinsella, 1976). Omotoso, (2006) found
that the emulsion capacity of larva Cirina forda averged 36.67%, while
emulsion stability was 45.36%. These relatively high levels of emulsion
capacity and emulsion stability suggested that C. forda would be highly
desirable for preparing comminuted meats. Emulsifying (EA) activity is
one of the most important functional properties of food proteins. Separate
hydrophobic and hydropilic regions are distributed in protein molecules
(amphiphilic structure). This structure is required for the formation of
emulsions (Kinsella, 1979). The emulsion stability (ES) measures the
tendency for the emulsion to remain unchanged. The ability of protein to
stabilize an oil in water emulsion is one of the most important functional
properties with respect to application in food products such as finely
comminuted meats, soups, cakes and salad dressings (Jackman et al,
1989).
2.10. Wettability:
Wettability properties depend on the affinity of the protein to water and
other polar solvent (Abdelkareem and Brennan, 1974).
Ease of
wettability is important in food formulations. Wettability of proteins is
affected by surface polarity, topography, texture, area and by the size and
microstructure of the protein particles but not necessarily by the amount
of native structure (Hagerdal and Lofqvist, 1978).
2.11 Dispersibility:
Ease of dispersibility is important in food formulations. The dispersibility
of a mixture in water indicates its reconstitutability. The higher
dispersibility the better (Kulkarni et al, 1991). Temperature, ionic
composition, pH and degree of agitation of the solvent are major factors
affecting dispersibility (Kinsella, 1976).
2.12.Water Retention Capacity (WRC)
Water retention is a basic functional property of
food
components
carbohydrates
such
(Zayas
and
as
Lin,
proteins
1989).
and
Water
retention is defined as the ability of the food
material to hold water against gravity (Hansen,
1978 and Chou and Morr, 1979). Water holding
capacity by protein is a function of several
parameters including size, shape conformational
characteristic,
stairs
factors,
hydrophilic-
hydrophilic balance of amino acids in the protein
molecules, lipids and carbohydrates associated
with the protein, thermodynamic properties of the
system (energy of bonding, interfacial tension,
etc). physico-chemical emvirnopenmnt (pH, ionic
strength, vapor , pressure, temperature presence
or absence of surfactant, etc) and solubility of
protein molecules (Chou and Morr, 1979). The
degree of water retention is considered to be
useful as an indication of performance for several
food formulations, especially those involving
dough handling (circle and Smith, 1972) a. Water
retention has been used as criteria for selection
of protein additives for food systems especially
meat products (Lin and Zayas, 1987).
CHAPTER THREE
MATERIALS AND METHODS
3.1 Materials:
Two samples of boiled and fried tree locusts ((Anacridium melanorhodon
melanorhodon)) were obtained from Mayo local market – Khartoum.
Refined Ground nut oil was brought from Bittar Co.ltd., Khartoum.
Sudan. Unless otherwise stated all chemicals used in this study were of
reagent grade.
3.2 Methods:
3.2.1 Samples preparations:
Locust was first cleaned, freed from foreign matter, separated inedible
part and milled in a laboratory miller to pass through 0.4 mm screen. To
extract oil from milled flour, cold extraction method was used. The flour
was placed in a conical flask and mixed with hexane (10:1). The mixture
was stirred using a mechanical shaker for 16 hours and then filtered. The
filtrate was washed again with hexane to remove traces of oil. The
mixture was filtered again and the oil free flour was dried in an open air
at room temperature. The dried flour was then ground to pass through
0.4mm screen and stored at 0 ºC for further analysis.
3.2.2 Protein Content:
Protein content determinations were made on the defatted sample by
micro -kjeldahl technique following the method of AOAC (1984).
3.2.3 Determination of nitrogen solubility at various pH values:
Nitrogen solubility of both boiled and fried flour was determined at
different pH values (2, 4, 6, 8, 10) by the procedure of Hagenmaier
(1972), modified by Quinn and Beuchat (1975) with a slight
modification. 0.2 grams material were suspended in 10 ml distilled water
and mechanically shaken for 15 minutes before the desired pH was
maintained by addition of 1N HCL or 1N NaOH. The suspension was
shaken for another 45 minutes at room temperature, centrifuged at 3000
rpm for 20 minutes at room temperature, and soluble nitrogen in the
supernatant was estimated by the micro-kjeldahl method. Percent protein
extracted was calculated with reference to the total amount of protein in
the sample.
Soluble protein = T x N x Tv x 14 x 6.25 x 100
A x b x 1000
Where T = Titre reading.
N
= Normality of acid. (0.02N).
Tv
= Total volume of aliquot extracted.
14 = each ml of hydrochloric acid is equivalent
to 14 mg nitrogen.
a = Number of ml of aliquot taken for
digestion.
b
= Number of (gm) sample flour extracted.
1000
6.25
= No. of mg in one gm.
= protein factor.
Percent solubility =
soluble protein x 100
crude protein of the sample
3.2.4 Determination of nitrogen solubility at different NaCl solutions:
Nitrogen solubility of both boiled and fried flour was determined at
different NaCl solutions by the procedure of Hagenmaier (1972), as
described by Quinn and Beuchat (1975) with a slight modification. 0.2
grams material were dispersed in 10 ml distilled water or NaCl solutions
ranged from (0.2-1M) and mechanically shaken for 1 hour at room
temperature, centrifuged at 3000 rpm for 20 minutes at room temperature,
and soluble nitrogen in the supernatant was estimated by the microkjeldahl method. Nitrogen solubility was expressed as percent of the
nitrogen content of the sample.
Soluble protein = T x N x Tv x 14 x 6.25 x 100
A x b x 1000
Percent solubility =
soluble protein x 100
crude protein of the sample
3.2.5 Functional properties:
3.2.5.1 Water retention capacity (WRC):
The Water Retention Capacity (WRC) was estimated by the method of
Lin et al (1974) with modification described by Quinn and Beuchat
(1975). A 10% suspension (1g/10ml) was stirred in a centrifuge tube
using a glass rod for 2 minutes at room temperature (26ºC). After 20
minutes equilibration the suspension was centrifuged for 20 minutes at
4400 rpm at room temperature (26ºC). The freed water was decanted into
a 10 ml graduated cylinder and the volume was recorded. (WRC) was
recorded as ml water retained by 100 grams materials.
3.2.5.2 Fat absorption capacity (FAC):
The Fat Absorption Capacity (FAC) of the sample was measured by a
modified method of Lin et al (1974). Four gram of the sample was
treated with 20 ml of refined groundnut oil a 50 ml centrifuge tube. The
suspension was stirred with a glass rod for 5 minutes and the contents
were allowed to equilibrate for a further 25 minutes at room temperature
(26ºC). The suspension was centrifuged for 20 minutes at 5000 rpm at
room temperature (26ºC).
The freed fat was decanted into a 10 ml
graduated cylinder and the volume was recorded. (FAC) was expressed as
ml oil pound by 100 grams dry matter.
3.2.5.3 Bulk density (BD):
The bulk density was determined by the method of Wang and Kinsella
(1976)a. About 3 grams of material were placed in a 25ml graduated
cylinder and gently packed by tapping the cylinder on the bench (10)
times to a reasonable height (approximately 5-8cm). The volume of the
sample was recorded . Bulk density was calculated as gram per milliliters
of material.
3.2.6 Emulsification properties:
3.2.6.1 Emulsification capacity (EC):
The Emulsification Capacity (EC) of the sample was estimated by the
method of Beuchat et al (1975). One gm material was blended with 50
ml of distilled water or NaCl solutions ranged from (0.2-1 M) for 30 sec.
in a Braun electric blender; after complete dispersion, refined groundnut
oil was added cautiously (0.4 ml/sec) from a burette and blending
continued until there was a phase separation (visual observation/change
in shaft sound). EC was expressed as milliliters of oil emulsified by one
gram material. EC was also determined as a function of different pHs
(2,4,6.8.10). The pH was adjusted to the desired value with either 1N
HCl or 1N NaOH prior to emulsion preparation.
3.2.6.2 Emulsification activity (EA) and emulsion stability (ES):
The emulsification activity (EA) was measured by the procedure of
Yatsumatsu et al (1972). About 0.7 gm of material was added to 10 ml
of distilled water or 10 ml of NaCl solutions ranged from 0.2 to 1M and
mixed well before adding to it 10 ml of refined Groundnut oil. The
mixture was blended in Broun electric blender for 5 minutes, poured into
centrifuge tubes and centrifuged at 2000 r.p.m for 5minutes then poured
into 50 ml measuring cylinders and stay a few minutes until the
emulsified layer was stable. EA was expressed as:
EA =
Height of emulsified layer
x 100
Height of total content of in the tube
EA was also determined as a function of selected pH values (2, 4, 6, 8,
10).
Emulsion stability (ES) was measured by recentrifugation followed by
heating at 80ºC for 30 minutes. And subsequently cooled to 15ºC. After
centrifugation the emulsion poured into 50 ml measuring cylinders and
stays a few minutes until the emulsified layer was stable. ES was
expressed as the percent of the total volume remaining emulsified after
heating.
ES =
Height of emulsified layer after heating x 100
Height of total content of in the tube
ES was also determined as a function of selected pH values (2, 4, 6, 8,
10).
3.2.7 Foaming properties:
3.2.7.1 Foaming capacity (FC):
Foaming capacity of the sample was determined by following the
procedure described by Lawhon et al (1972).
2 grams of the sample
were blended with 100 ml distilled water or 100 ml NaCl solutions
ranged from (0.2-1M) in a moulinex blender at "hi" speed for 2 minutes.
The mixture was poured into a 250 ml measuring cylinder and the foam
volume was recoded after 30 sec.
FC = Volume after whipping - Volume before whipping x 100
Volume before whipping
FC was also determined as a function of different pH values (2, 4, 6, 8,
10).
3.2.7.2 Foam stability (FS):
The foam stability (FS) was conducted according to Ahmed and Schmidt
(1979). The FS was recorded at 15 minutes interval for 2.30 hours after
pouring the material in a cylinder.
FS = Foam volume after time (t) x 100
Initial foam volume
FS was also determined as a function of selected pHs (2, 4, 6, 8, 10).
3.2.8 Gelation:
Least gelation concentration of the sample was measured by the method
of Coffman and Garcia (1977) with a slight modification. Appropriate
sample suspensions of (2, 4, 6, 8 and 10%) were prepared in 10 ml of
distilled water or 10 ml NaCl solutions ranged from (0.2-1 M). The test
tubes containing these suspensions were then heated for one hour in a
boiling water bath followed by rapid cooling under running cold tap
water. The test tubes were further cooled for 3 hours at (4ºC). The least
gelling concentration was determined as that concentration did not fall
down or slip when the test tube was inverted.
Least gelation
concentration of the same concentration in distilled water was also
determined as function of selected pH values (3, 7, and 10).
3.2.9 Dispersibility:
The despersibility of flour at selected pH levels (3, 7, 10) was measured
according to the method of Kulcarni, Kulcarni and Ingle (1991). 3 grams
of the flour was dispersed in distilled water in a 50 ml stoppered
measuring cylinder and the desired pH was adjusted by addition of drops
of dilute HCl and NaOH solutions. Then distilled water was added to
reach a volume of 30 ml, The mixture was stirred vigorously and allowed
to settle for three hours ,the volume of settled particles was subtracted
from 30 and multiplied by 100 and reported as percentage dispersibility.
3.2.10 Wettability:
The Wettalability was estimated to both untreated
and treated samples according to the method of
Regenstein and Regenstein, (1984).
Two grams
of the sample were weight in a sieve and
transferred to a beaker containing 80 ml distilled
water and a magnetic without stirring the water.
The behavior of the powder was observed on the
water
surface
immediately
after
adding
the
sample. After 30-min. observation the material
was stirred on the magnetic stirrer sufficiently
fast to form a vortex which reached the bottom of
the beaker. The stirring continued for one min.
after which the grade describing Wettability was
recorded
as
excellent,
good,
fair
or
poor
according to the time and behavior of the
dispersion (see Chart 1).
Chart 1 Wettability grade according to respective characteristics
Characteristic of wet sample
* Powder wet as soon as it contacts water, even Excellent
with stirring. After one half hour, the sample is
completely dispersed.
* Powder only wets slightly when it comes into Good
contact with water. After one half hour the
sample is wet and powder had sunk to the
bottom. Stirring disperse the sample.
* Powder wets very slightly on initial contact Fair
and tend to clump and remain at the surface.
After one half hour the sample still after the
surface although some of the sample has
disperse. After stirring there are still a few
clumps left.
* Powder hardly wets when it initially comes in Poor
contact with the water. It also clump. After one
half hour the solutions is lightly cloudily and
most of the sample is still in clump0s at the
surface. After stopping the stirring most of the
sample still floats and clumps.
CHAPTER FOUR
4. RESULTS AND DISCUSSION
4.1. Proximate composition of boiled and fried tree locust:
The results of the proximate composition of
boiled and fried tree locust flour are shown in
table 1.
The moisture content of boiled and fried tree
locust flour were of no significant difference,
compared to the fried one, which were quite low
(5.467±0.06,
7.470±0.21)
.This
may
be
advantageous in view of the samples shelf life.
As shown in table 1, the protein content of the boiled tree locust flour was
significantly higher than that of fried one. However results indicated that
both boiled and fried tree locust are quite rich in protein (66.24±0.02,
67.75±0.03). The values obtained in this study are higher than those of
the larval (50.39% ±2.01), and adult (53.10%±0.56 stages of Zonocerus
variegates) as reported by Adedire and Aiyesanmi (1999). Thus boiled
and fried tree locust flour could contribute significantly to the
recommended human daily protein requirement of 23-56% stipulated by
NRC (1980).
The ash content of the boiled tree locust flour showed no significant
difference compared to that of a fried one. The result obtained here are
lower than those of termites (13.90%) obtained by Ajakaiye and Bawo
(1990). The results showed that the crude fiber content of boiled locust
was higher significantly than that of a fried one.
Table 1 Proximate (%) composition of boiled and fried locust
Treatment
Parameters
Crude protein
Crude fiber
Ash
Moisture
Fried
67.7 ±(0.03) a
7.317±(0.12)
6.017±(0.18) a
5.467±(0.06) a
Boiled
66.24 ± (0.02) b
8.377±(0.02)b 5.533± (0.38) a
7.470±(0.21) a
F-ratio
5570.967***
248.462***
258.74***
C.V%
a
0.04%
1.05%
4.024*
5.11%
2.36%
Values are means (±SD) having different superscript letters in columns
differ significant (P0.05)
(2) n.s not significant, * significant, ** moderate significant ** highly
significant
4.2. Effect of NaCl Concentration on emulsification activity (EA) of
boiled and fried tree locust flour:
Table 2 shows the EA of the boiled and fried tree
locust samples at different NaCl concentrations.
The results indicated that for the boiled samples,
the EA decreased significantly (P≤0.05) with the
increase of NaCl concentration up to 0.4M and
then increased significantly (P≤0.05) at6M. The
lowest value of EA was obtained at 0.4M, and the
maximum value was obtained in the absence of
NaCl. The results agreed with that reported by
Mahmoud (2004) who stated that the EA of
chickpea was higher in distilled water, and then
decreased at 0.2M NaCl, but no obvious reduction
was observed after 0.6M salt concentrations. For
fried samples the results revealed that the EA was
improved with the addition of salt regardless of
its concentration. The results also showed that in
the lack of NaCl, the EA of fried samples was
significantly higher than that of boiled samples.
This finding was agreed with that reported by
Mahmoud (2004) who concluded that application
of high heat decreased the emulsification activity.
4.3. Effect of NaCl Concentration on
emulsification capacity (EC) of boiled and fried
tree locust flour:
Table (3) shows the result of emulsification
capacity of the boiled and fried tree locust
samples at different NaCl concentrations. The
results showed that for the boiled samples, the
emulsification
capacity
increased
significantly
(P≤0.05) with increase in NaCl concentration up to
0.6M and then decreased. The lowest value was
that obtained at 0.4M concentrations, while the
maximum value of the emulsification capacity
was at the absence of the salt
Emulsification activity (%) of boiled and Table 2:
fried tree
locust flour at different NaCl
concentrations
Fried
42.0f
56.3a
Boiled
NaCl cocn.
55.5a
50.0cde
0.0
0.2
51.6bcd
46.6e
0.4
52.0abc
51.3d
0.6
53.9abc
50.0cde
50.0cde
47.7d
SE±1.56
Any two mean values having different superscript letters differ
significantly (P≤0.05).
0.8
1.0
Emulsification capacity(%) of boiled and Table 3:
fried tree
locust flour at different NaCl
concentrations
Fried
boiled
NaCl cocn.
1.86 de
1.80e
0.0
2.36 b
0.2
2.03cd
2.13c
2.56ab
0.4
2.73a
2.73a
0.6
1.83d
1.93cde
1.0
0.8
1.30f
1.20f
SE±0.068
Any two mean values having different superscript
letters differ significantly (P≤0.05).
The present findings disagreed with that reported
by Narayana and Narasiga (1982) who found that
incorporation of NaCl up to 0.4M increased
emulsification capacity of wing bean flour. This
variation may be due to the difference between
the samples. Nakai (1983) stated that emulsion
property cannot be solely due to proteins, but it
depends
on
other
constituents
such
as
carbohydrates and lipids. Moreover, the same
trend was observed for fried samples, On the
other
hand
no
significant
differences
were
observed for emulsification capacity between
boiled and fried samples at all concentration of
NaCl.
4.4. Effect of NaCl Concentration on emulsion stability (ES) of boiled
and fried tree locust flour:
As shown in table 4, the emulsion stability of
boiled
tree
locust
flour
at
different
NaCl
concentrations, decreased significantly (P≤0.05)
with the addition of NaCl, and beyond 0.2 M
concentration it increased significantly, and then
decreased. The lowest value of emulsion stability
was obtained at 1.0 M, and the maximum value
was obtained in the absence of NaCl. The results
were
in
agreement
with
that
reported
by
Mahmoud (2004) who stated that addition of NaCl
significantly decreased the emulsion stability of
untreated flour, and also found that higher
emulsion stability values were observed when
distilled water was used without addition of NaCl
(92.67%) and then decreased considerably to
42.05 and 3.48% at 0.2M and 0.8M NaCl,
respectively. On the other hand, the fried samples
results indicated that the emulsion stability was
improved with the addition of salt, till 0.6 M, and
then decreased beyond it. Similar observation was
reported by Odoemelam (2005) who concluded
that, addition of NaCl improved the emulsion
stability.
Emulsion stability (%) of boiled and
Table (4):
fried tree
locust at different NaCl concentrations
Boiled
cocn.
NaCl
Fried
42.9f
60.0a
0.0
53.8bcd
53.0cd
0.2
56.8abc
58.3ab
0.4
60.4a
60.0a
0.6
58.7ab
51.0de
0.8
52.4cd
46.2ef
1.0
SE±1.70
Any two mean values having different superscript
letters differ significantly (P≤0.05).
The results also showed in the absence of NaCl
the
emulsion
stability
of
fried
sample
was
significantly higher than that of boiled one. This
may be due to the effect of high heat treatment of
frying
process.
application
of
It
was
high
reported
heat
that
the
decreased
the
emulsification stability (Pawar and Ingle, 1988).
4.5. Effect of NaCl Concentration on foaming
capacity (FC) of boiled and fried tree locust flour:
Table 5 illustrates the change of foaming capacity
of the boiled and fried tree locust flour at
different NaCl concentrations. It was observed
that
no
consistent
pattern
of
change,
as
concentration of NaCl increased for the boiled
samples. The lowest value of foaming capacity
was observed at 0.2M NaCl concentration, while
the maximum value observed at 0.6M NaCl. For
the fried samples the results indicated that the
foaming capacity was improved with addition of
salt till 0.4M NaCl and then decreased. The
results obtained disagree with that reported by
Mahmoud (2004) who found that the maximum
improvement of foaming capacity for chickpea
was observed at 0.2M NaCl, while higher foaming
capacity was observed at low salt concentration.
Variation
in
these
results
may
be
due
to
difference in the tested protein sources. Kinsella
(1976) stated that foaming capacity at different
concentrations of salt is usually affected by the
protein solubility at the interface of the colloidal
suspensions during foam formation
4.6. Effect of NaCl Concentration on foam
stability (FS) of boiled and fried tree locust flour:
The effect of Nacl concentration on foam stability
(FS) of boiled and fried tree locust flour is shown
in tables 6 a and 6 b, respectively.
Foaming capacity (%) of boiled and fried Table 5:
tree locust at
different NaCl concentrations
Fried
Boiled
NaCl cocn.
0.001c
16.13a
0.0
4.86b
5.60b
0.2
4.86b
17.33a
0.4
3.00bc
18.33a
0.6
1.00c
16.00a
0.8
1.00c
17.33a
1.0
SE±1.21
Any two mean values having different superscript
letters differ significantly (P≤0.05).
Table 6 a: Effect of NaCl concentration on foam stability (%) of
boiled tree locust flour
Time
NaCl concentration (M)
(min)
0.0
0.2
0.4
0.6
0.8
1.0
0
100.0
100.0
100.0
100.0
100.0
100.0
15
90.33 a
97.20 a
93.20 a
90.26 a
95.46 a
95.46 a
30
87.86 a
96.60 a
91.63 a
88.83 a
92.53 a
92.53 a
45
87.86 a
95.60 a
87.53 a
88.33 a
88.53 a
91.46 a
60
86.93 a
95.30 a
87.53 a
88.33 a
86.76 a
88.63 a
75
86.60 a
95.70 a
87.53 a
88.20 a
36.76 a
88.00 a
90
86.60 a
94.70 a
87.0 a
88.20 a
86.76 a
88.06 a
105
86.60 a
86.56 a
86.76 a
88.06 a
86.36 a
88.06 a
120
86.40 a
86.50 a
86.76 a
88.06 a
86.36 a
86.36 a
135
84.40 a
85.86 a
85.93 a
86.76 a
86.36 a
86.36 a
150
84.11 a
85.86 a
84.56 a
86.76 a
85.83 a
85.80 a
SE±31.24
Any two mean values having different superscript letters differ
significantly (P≤0.05).
Table 6 b: Effect of NaCl concentration on foam stability (%) of fried tree
locust flour
Time
NaCl concentration (M)
(min)
0.0
0.2
0.4
0.6
0.8
1.0
0
100.0
100.0
100.0
100.0
100.0
100.0
15
0.001
95.66a
95.56 a
100.0 a
99.0 a
99.0 a
30
0.001
95.66 a
95.56 a
99.0 a
98.10 a
99.0 a
45
0.001
95.66 a
95.56 a
98.10 a
98.10 a
99.0 a
60
0.001
95.66 a
95.56 a
98.10 a
98.10 a
99.0 a
75
0.001
95.66 a
95.56 a
98.10 a
98.10 a
99.0 a
90
0.001
94.70 a
90.0 a
86.46 a
86.76 a
88.06 a
105
0.001
94.40 a
86.40 a
84.56 a
86.76 a
88.06 a
120
0.001
94.40 a
86.40 a
84.56 a
86.76 a
86.06 a
135
0.001
94.40 a
85.86 a
84.56 a
86.76 a
86.06 a
150
0.001
94.11 a
85.86 a
84.56 a
86.76 a
85.83 a
SE±31.24
Any two mean values having different superscript letters differ
significantly (P≤0.05).
Foam stability of boiled locust flour (table 6a)
was found to be depend on NaCl concentration.
At a given time significant changes were observed
in foam stability (FS) as NaCl concentration was
increased. As shown in table 6a when the foam
stands for 45 min, the foam stability increased
from 87.86 to 95.6% and thereafter fluctuated.
For fried locust (Table 6b) similar trend was
observed except in the absence of the salt, where
no foam was formed.
The results obtained disagreed with that reported by Mahmoud, (2004)
who found that as the salt concentration increase the FS of chickpea flour
increased significantly, and also disagree with that reported by
(Mahajan,1999) who stated that the FS was better at 0.2-0.6 M NaCl.
However this results is supported by the findings of Bera and Mukherjee
(1989) who reported that the foam stability of rice bran concentrates,
slightly improved when salt concentration was increase from 0.1M to
1.0M NaCl. This variation may be due to the fact that the foam stability
(FS) is governed by the cross linking of protein molecules and creation of
films. (Mahmoud, 2004).
4.7. Effect of NaCl Concentration on protein
solubility of boiled and fried tree locust flour:
Table 7 showed the results of flour solubility of
the boiled and fried tree locust flour at different
NaCl concentrations. These results indicated that
for the boiled samples, the flour solubility remain
constant as NaCl concentration increased till 0.8M
NaCl and then slightly increased. The maximum
value obtained at 1.0M NaCl.
These present
finding agree with that reported by Mahajan
(1999) who stated that protein solubility was
improved in the presence of NaCl. Moreover, for
the fried samples, the results indicated that the
protein solubility was improved with addition of
salt, till 0.4M and thereafter started to decrease.
`
flour solubility (%) of boiled and fried
tree locust at
different NaCl concentrations
Fried
Boiled
Table (7):
NaCl Cocn.
23.43b
23.06b
0.0
23.73b
23.90b
0.2
27.13a
23.90b
0.4
23.33b
23.63b
0.6
0.8
23.66b
24.56b
23.30b
24.30 b
1.0
SE±0.44
Any two mean values having different superscript
letters differ significantly (P≤0.05).
4.8. Effect of pH on emulsification activity (EA) of
boiled and fried tree locust flour:
Table 8 shows the results of emulsifying activity
of boiled and fried tree locust at different pH
values. The results indicated that, for the boiled
samples, the lower value was observed at pH 6
(46.30), and on the other side of this pH it was
significantly increased. This result agreed with
that reported by Massoura et al. (1996) who
found that the lower emulsifying activity occurred
at pH 6 due to low protein solubility at this pH.
While for the fried samples the lowest emulsifying
activity occurred at pH 2 (25.33)
and the
maximum occurred at pH 8 (40.1). The results
obtained agreed with that found by Yim and Lee
(2000); Khalid et al. (2002) and Monteiro and
Prakash (1994) who observed higher emulsifying
activity of soybean, sesame and peanut proteins,
respectively at alkaline pH than at acidic one.
Variation in results between boiled and fried
samples might be due to processing effect which
may cause protein interaction that affected the
surface hydrophobicity and the net charged of the
protein (Mahmoud, 2004).
4.9. Effect of pH on emulsification capacity unit
(EC) of boiled and fried tree locust flour:
Results of Table 9 illustrated the emulsification
capacity of both boiled and fried samples at
different levels of pH. It was observed that the
emulsification capacity was affected by pH, where
it was high at acidic region ( pH 2), and the lowest
value was observed at alkaline (pH 8). These
results were disagreed with that obtained by Idris
(2003) who found that the lower value of
emulsification capacity was observed at acidic pH
5. This variation possibly might be due to
variation in chemical nature of tested samples.
Emulsification activity (%) of boiled and Table 8:
fried tree
locust at different pH values
Fried
25.33f
31.46e
39.96d
40.10d
33.93e
Boild
pH
67.50a
56.50b
2
4
46.30c
53.20b
72.23a
6
8
10
SE±1.70
Any two mean values having different superscript
letters differ significantly (P≤0.05).
Emulsification capacity (%) of boiled
and fried tree
Locust flour at different pH values
Fried
11.83a
Table (9):
Boild
8.83b
pH
2
6.00e
7.33cd
4
8.00c
7.00d
6
4.23f
5.50e
8
4.66f
7.00d
10
SE±0.23
Any two mean values having different superscript
letters differ significantly (P≤0.05).
4.10. Effect of pH on emulsification stability (ES)
of boiled and fried tree locust flour:
Table 10 presents the results of emulsion stability
of boiled and fried tree locust at different pH
values. The results revealed that the change of
emulsion stability as affected by pH values was of
no consistent pattern for the boiled samples. The
lowest
value
of
emulsification
stability
was
observed at pH 8 (55.53), and the maximum was
observed at pH 6 (89.43).
These results obtained agreed with that reported
by
Mahmoud
(2004),
who
found
that
the
emulsion stability was higher at pH 6 (93.09%)
and it decreased at alkaline pH.
For the fried
samples the emulsion stability recorded low value
at pH 6 (25.66), but showed a remarkable
increase on either of this pH. Similar trend was
obtained by Khalid (1994) who found that the
emulsion stability of sesame protein isolate was
higher at acidic region of pH 7 (75%) than the
emulsification stability at alkaline region of pH 9
(62%) with a minimum emulsification stability at
pH 4.9 (37.8%).
4.11. Effect of pH on foaming capacity (FC) of
boiled and fried tree locust flour:
Table 11 shows the results of foaming capacity of
boiled and fried tree locust at different pH values.
The results showed that, for the boiled samples,
the lower value was observed at pH 8 (5.80) and
the maximum value was observed at pH 2 (40.0).
The fried samples, the lowest foaming capacity
was observed at pH 6 (7.80) and the maximum
value was observed at pH 2 (39.20). This result
disagreed with that reported by Odoemelam
(2005) who stated that the capacity to produce
foam was pH dependent with a maximum value at
pH 4.0.
Emulsification stability (%) of boiled
and fried tree
locust at different pH values
Fried
29.90d
Table 10:
Boiled
68.80b
pH
2
28.63d
58.33c
4
25.66d
89.43a
6
26.70d
55.53c
8
28.33d
76.86b
10
SE±2.72
Any two mean values having different superscript
letters differ significantly (P≤0.05).
Foaming capacity (%) of boiled and
fried tree locust at
different pH values
Table 11:
Fried
Boiled
39.2b
40.0a
2
23.1f
22.3e
4
7.8h
11.5g
6
11.5g
31.4c
pH
5.8i
23.6d
8
10
SE±0.01
Any two mean values having different superscript
letters differ significantly (P≤0.05).
4.12. Effect of pH on foam stability (FS) of boiled
and fried tree locust flour:
The effect of pH values on foam stability of boiled
and fried tree locust flour is shown in Table 12a
and 12b, respectively. The results showed that
the boiled samples at both acidic and alkaline pH
significantly differed at a given time (Table 12a).
When the foam stands for 45 min, the foam
stability increased with increase in pH8 value till
pH and then started to decreased. For the fried
locust (Table12b) at pH 2 no significant difference
was observed with time up to 90 min. while for
pH 4, 6 and 8 no significant difference beyond 45
min, Moreover for both boiled and fried samples
at a given time significant changes were observed
but not consistent at both acidic and alkaline
range of pH. On the other hand, the results
indicated that the FS of the boiled samples at
different pH values and for different times was
significantly different. This results was supported
by what was reported by (Idris, 2003 ) who stated
that the FS was greatly affected by pH.
4.13. Effect of pH on protein solubility of boiled
and fried tree locust flour:
Table
13
illustrates
the
results
of
protein
solubility of boiled and fried tree locust at
different pH values. For the boiled samples,
minimum protein solubility was observed at pH 8,
and the highest value was observed at pH 10.
While for that of fried samples it decreased at pH
2
and
pH
4
and
then
started
increased
considerably. The results of fried samples agreed
with that reported by Fagbemi et al. (2006) who
stated
that
minimum
protein
solubility
was
observed at pH 4 and the maximum protein
solubility was observed at pH 9. Generally, the
dependency of protein solubility on pH has been
attributed to the change in the net charges
carried by protein as the pH changes (Fagbemi et
al., 2006). It was observed that when the locust
flour was boiled the isoelectric pH shifted from 4
to 8 due to change in protein nature as a result of
heating
Table I2a. Effect of pH on foam stability (%) of boiled tree locust
flour
pH
Time
(min)
2
4
6
8
10
0
100.0
100.0
100.0
100.0
100.0
15
66.70a
88.70 a
98.30 a
98.20 a
88.10 a
30
65.70 b
85.70 b
96.60 b
97.30 b
86.80 b
45
65.70 b
84.10 c
94.80 c
96.40 c
85.30 c
60
63.80 c
84.10 c
94.0 d
96.40 c
85.30 c
75
62.90 d
84.10 c
94.0 d
96.40 c
83.30 d
90
62.90 d
84.10 c
93.1 e
96.40 c
82.40 e
105
62.90 d
82.50 d
93.1 e
96.40 c
82.40 e
120
62.90 d
82.50 d
91.4 f
96.40 c
82.40 e
135
62.90 d
82.50 d
91.4 f
96.40 c
82.40 e
150
62.90 d
82.50 d
91.4 f
96.40 c
82.40 e
SE±0.014
Any two mean values having different superscript letters differ
significantly (P≤0.05).
Table 12b Effect of pH on foam stability (%) of fried tree locust flour
Time
pH
(min)
2
4
6
8
10
0
100.0
100.0
100.0
100.0
100.0
15
77.70a
95.30a
95.50a
98.30a
97.0a
30
77.70a
93.80 b
95.50 a
96.60 b
89.60 b
45
77.70 a
92.20 c
94.50 b
96.60 b
88.10 c
60
77.70 a
90.60 d
94.50 b
94.80 c
86.60 d
75
77.70 a
90.60 d
94.50 b
94.80 c
86.60 d
90
76.70 b
90.60 d
94.50 b
94.80 c
85.10 e
105
76.70 b
90.60 d
94.50 b
94.80 c
85.10 e
120
76.70 b
90.60 d
94.50 b
94.80 c
79.10 f
135
76.70 b
90.60 d
94.50 b
94.80 c
79.10 f
150
62.90 b
90.60 d
94.50 b
94.80 c
79.10 f
SE±0.014
Any two mean values having different superscript letters differ
significantly (P≤0.05).
Flour solubility (%) of boiled and
fried tree locust at
different pH values
Fried
Boiled
20.03d
21.46cd
Table (13):
pH level
2
18.06e
22.70c
4
20.80d
22.66c
6
22.03cd
4.76f
8
25.56b
26.36a
10
SE±0.48
Any two mean values having different superscript
letters differ significantly (P≤0.05).
4.14. Effect of NaCl concentration on the least gelation concentration of
boiled and fried tree locust flour:
The effect of NaCl concentration on the least gelation concentration of
boiled and fried tree locust flour is shown in table 14a and 14b. for the
boiled samples (table 14a), NaCl concentration had no effect on least
gelation of the flour except at 1.0M a weak gel was obtained when 6 –
10% flour concentrates was used. For fried locust (Table 14b) simslar
trend was observed. The results obtained disagree that was reported by
Ogungbenle (2002) who found that the lower least gelation was 18%
(w/ml) in the absence of salts and was improved in the presence of
different salt concentration and was found to be was found between 12
and 16% (W/ml).
4.15. Effect of the pH on the least gelation concentration of boiled and
fried tree locust flour:
Table 15 shows the effect of pH on the least gelation concentration of
boiled and fried tree locust flour. The results indicated that the pH had no
effect on the least gelation concentration except at 10% for both boiled
(Table 15a) and fried (Table 15b) tree locust flour. This may be attributed
to the fact that gelling ability is governed by protein and it is nature, it
was reported that higher globular protein contribute to higher least
gelation value Sathe et al, (1982). This results disagreed with that
reported by Mahmoud (2004).
4.16. Effect of pH on dispersibility (%) of boiled and fried tree locust
flour:
As shown in Table 16, the dispersibility of boiled samples was lowered at
neutral pH but showed remarkable increase in either side of pH for fried
Samples, the pH changes had no effect on dispersibility of the flour.
Table 14a : Effect of NaCl concentration on the least gelation
concentration of boiled tree locust flour:
NaCl Solution
Concentration
(M)
2%
4%
6%
8%
10%
0.0
-
-
-
-
-
0.2
-
-
-
-
-
0.4
-
-
-
-
-
0.6
-
-
-
-
-
0.8
-
-
-
-
-
1.0
-
+: weak gel
-
+
+
+
- : no gel
Table 14b : Effect of NaCl concentration on the least gelation
concentration of fried tree locust flour:
NaCl Solution
Concentration
(M)
2%
4%
6%
8%
10%
0.0
-
-
-
-
-
0.2
-
-
-
-
-
0.4
-
-
-
-
-
0.6
-
-
-
-
-
0.8
-
-
-
-
-
1.0
-
-
+
+
+
+: weak gel
- : no gel
Table 15a : Effect of pH concentration on the least gelation concentration
of boiled tree locust flour:
pH values
+: weak gel
2%
4%
3
-
-
7
-
10
-
Concentration
6%
8%
10%
-
-
+
-
-
-
+
-
-
-
+
- : no gel
Table 15b : Effect of pH concentration on the least gelation concentration
of fried tree locust flour:
pH values
2%
4%
3
-
-
7
-
10
-
+: weak gel
Concentration
6%
8%
10%
-
-
+
-
-
-
+
-
-
-
+
- : no gel
Table 16 .Effect of pH on dispersibility (%) of boiled and fried tree locust
flour:
pH
boiled
fried
3
70.0% (±2.0)
66.7 %(±2.8)
7
66.7 % (±1.7)
66.7 %(±2.6)
10
73.3%(±3.3)
66.7 %(±2.7)
Table 17. Fat and water absorption capacity and bulk density of boiled and
fried tree locust flour
Property
Boiled
Fried
Fat absorption capacity
165(±2.5)
675(±2.70)
2.93(±0.03)
2.47(±0.06)
0.14(±0.05)
0.15(±0.42)
(ml/100 g)
Water absorption capacity
(ml/100 g)
Bulk density (g/ml)
These results disagreed with that reported by Mahmoud (2004) who
stated that dispersibility of chick pea was higher at pH 7.
4.17. Water and fat absorption capacity
(WAC/FAC) of boiled and fried tree locust:
Water and fat absorption capacity of boiled and fried tree locust flour
samples are shown in Table 17. The WAC of boiled tree locust flour was
2.93 mg/l00g, which was higher than that of check pea flour 2.3 ml/gram
as reported by Odoemelam, (2005), while for fried samples it was (2.47
ml/100g). The result is supported by that reported by Odoemelam,
(2005), who found that water absorption capacity of heat processed flour
was lower than that before processing. Fat absorption capacity, of boiled
tree locust flour was 165 ml boil/100 gram which was higher than that of
pumpkin seed flour as found by Fagbemi et al., (2005). And that of chick
pea flour as reported by (Mahmoud, 2004). For fried samples the FAC
value was 675 ml oil/100 gram, which was higher than that of boiled
samples. The result obtained is similar to that reported by Enujiugha et al,
(2003) who found that the application of high heat increased FAC.
4.18. Bulk density (BD) of boiled and fried tree
locust:
As shown in Table 17 the BD of boiled tree locust
was 0.14g/ml which is lower than that of check
pea flour observed by Mahmoud, (2004) and that
of cowpea as reported by Padmashree et al
(1987).Variation in BD may be due to the
variations in chemical nature of the samples as
well as the particle size. However the BD of fried
sample was slightly higher than that of boiled
one. The present finding is in line with that
reported by Ventesh and Parakash (1993) who
stated that the application of high heat increase
BD, and suggested that this may be due to dense
packing
of
particles
for
the
same
volume
resulting from removal of water.
4.19 wettability of boiled and fried tree locust:
The wettabilioty grade for both boiled and fried flour, were good since it
wet slightly after one min., when it comes into contact with water. It was
found that after 30 min wettability grade of boiled flour was good while
for fried it was excellent. Similar results were obtained by Mahmoud
(2004).
CHAPTER FIVE
CONCLUSIONS AND RECOMMENDATIONS
5.1. Conclusions:
The most significant conclusions, which can be derived from the work,
are the following:
1.
Both boiled and fried tree locust contained high levels of
protein 66.24 & 67.7%, respectively.
2.
Emulsification capacity and protein solubility of tree locust
flour were improved with the addition of NaCl.
3.
No or weak gel was formed for tree locust flour at different
NaCl concentration and pH levels.
4.
Emulsification activity, emulsification capacity and foaming
capacity were affected by pH for both boiled and fried samples,
with higher values at alkaline region, and lower values at acidic
range. .
5.2. Recommendations
Taking into account the conclusions described above, the following
recommendations should be considered:
1.
More consideration of tree locust flour as food protein source is
called for.
2.
It would be more appropriate to conduct trials of using tree
locust flour as raw materials as an animal food in processing.
3.
Study should be conducted to investigate the effect of different
method of processing on residual pesticides used to control the
insect.
4.
Further research is needed, in this field, for gaining a better
understanding
functionality
of
of
the
boiled
interrelationships
between
and
locust
fried
tree
the
flours
characteristics and their performance in specific food systems.
5.
Studies on the natural and external toxicants in different locust
flours need to be identified before using as raw materials for
feed and food processing.
6.
We have to establish a technique to detect pesticides in locust
before processing to avoid the risk of such chemicals.
7.
Further study regarding the protein structure (molecular weight
& amino acids composition) should be consider.
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