I.
1*
Jeličić ,
K.
2
Tonković ,
N.
3
Major ,
R.
1
Božanić ,
Lj.
2
Gregurek
1- Faculty of Food technology and Biotechnology, Department for Food Engineering, University of Zagreb, Pierottijeva 6, 10000 Zagreb, Croatia;
*[email protected]
2- Probiotik d.o.o., Zagreb, Croatia
3- Faculty of Food technology and Biotechnology, Department for Food Quality Control, University of Zagreb, Pierottijeva 6, 10000 Zagreb, Croatia
Sensory evaluation
Introduction
Panel sensory evaluation
Milk usually contains 4.8% of lactose in a dry matter which makes it the main
sugar in milk. However, many people suffer from lactose intolerance or lactose
insufficience which makes them partially or fully unable to digest lactose. In
case of consumption of milk and lactose containig dairy products this
population suffers unpleasant coseqeuences like cramps, abdominal pain,
abdominal bloating, gas or diarrhea. Besides that, there is also a risk of
suffering some of the above mentioned symptoms even after consumption of
yoghurt and other fermented dairy beverages due to the fact that they still
may contain lactose and that their dairy cultures may no longer be active or
may not survive the conditions in the digestive tract. Nowerdays there are
already products like lactose free milk on the market, but yet there are no
fermented beverages and/or yoghurt made from hydrolized milk.
A difference panel consisting of 10 members has been developed according to ISO 3972:1991
(E) Sensory analysis - Methodology - Method of investigating sensitivity of taste. Test persons
who had more than 65% of correct answers were chosen to enter the panel.
Panelists evaluated sweetness of yoghurts by using the Multiple paired comparison test where
sweetness of all possible pairs from the existing 12 samples had to be evaluated. Obtained
results were evaluated by a Friedman-type statistical analysis.
Additionally, panelists conducted an Multisample comparison test where the sweetness of
joghurts produced from the same milk type had to be ranked ona a scale from 0 (not sweet at
all) to 9 (extremely sweet). Obtained results were evaluated by comparing standard deviations
of each sample following ANOVA principle with p=5%.
Electronic tongue analysis
Alpha MOS ASTREE Electronic tongue (Picture 1) was used for sensory anlysis of all 12
samples. The detection system consists of 7 liquid sensors and a reference electrode. 90 mL
of every sample was poured into glasses which were placed into the automatic sampler. The
obtained results were evaluated by the method of Principal Components Analysis (PCA).
Objectives
Objectives of this work were to examine :
•Whether there is a significant difference in sweetness of yoghurts
produced from hydrolized and from non-hydrolized milk
Picture 1 Alpha MOS Astree electronic tongue
Results
•Whether there is a significant difference in sweetness of these two
yoghurts when adding fruit base containing artificial sweeteninig agent
respectively containing sugar
•Comparing mean values obtained by results from Multisample comparison tests among non
•Whether panel sensory evaluation of fruit yoghurts conducted by a
panel can be compared with results obtained by using electronic tongue
analysis
•Comparison of mean values among all 12 yoghurt samples showed that hydrolized milk
hydrolized milk yoghurt samples it is clearly that in all cases yoghurt with fruit base
containig artificial sweetening agent is sweeter. The same results are obtained by
comparing mean values among hydrolized milk yoghurt samples.
yoghurt samples are always sweeter regrdless the fruit base they contained.
•From results obtained by Multiple paired comparison tests critical values T and χ2
(α=0,05) have been calculated following principles of Friedman analysis. Among yoghurt
samples containing fruit base with sugar, comparison of critical values showed that milk
hydrolized yoghurts are sweeter. The sweetness is distributed according to the amount
of fruit base in yoghurt. Same results were obtained by comparing critical values among
Methods
yoghurt samples containing fruit base with artificial sweetening agent.
Yoghurt production
Milk Hydrolysis
1. Adding
MAXILACT® L
2000 (GistBrocades GmbH,
Germany)
2. Stirring for 20 h
at 6°C
•B- yoghurt from nonhydrolized milk
Milk
•BD – yoghurts from hydrolized milk
•Indexses 1, 5, 10 – amount of fruit base in %
Pasteurization
Cooling down to
43°C
Innoculation with
BT-10X and 100F
(DSM Food specialties,
Netherlands)
Picture 2. PCA analysis of yoghurts with fruit base containing artificial sweetening agent
Incubation
Cooling down to 20°C
at pH=4,6
Hydrolized milk
fruit yoghurt
Adding 1%, 5% or
10% of fruit base
with sugar/artificial
sweetening agent
Non-Hydrolized
milk fruit yoghurt
Fruit yoghurts made of hydrolized milk are significatly sweeter
than yoghurts made of non-hydrolized milk regardless to the
type of the added fruit base
Picture 2 showes results of Electronic tongue analysis of yoghurt samples containing fruit
base with artificial sweetening agent. PCA grouped all analyzed sample into two gropus.
First one was formed according to whether milk was hydrolized or not prior to yoghurt
production. The other group was formed according to the amount of fruit base among
each yoghurt type where swetness rises with the amount of fruit base.
Sweetnes intensity rises in following order = BD1 – B1 – BD5 – BD10 – B5 – B10, where
samples BD10 i B5 are most similar, while samples B1 i BD5 show most differences.
Aroma intensity of yoghurts rises with the mass content of
the added fruit base
Electronic tongue analysis grouped yoghurt samples according
Fruit yoghurts with addition of fruit base containing artificial
sweetening agent are significatly sweeter than those with
addition of fruit base containing sugar
to the type of raw material used for their production and
according to the content of the fruit base. These results could
not be exactly compared to the results obtained by the panel
sensory evaluation but point to similar conclusions.