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.

I. JeličićI. Jeličić11**, K. Tonković, K. Tonković22, N. Major, N. Major33, R. Božanić, R. Božanić11, Lj. Gregurek, Lj. Gregurek22

1- Faculty of Food technology and Biotechnology, Department for Food Engineering, University of Zagreb, Pierottijeva 6, 10000 Zagreb, Croatia; **irjelicic@pbf.hr

2- Probiotik d.o.o., Zagreb, Croatia3- Faculty of Food technology and Biotechnology, Department for Food Quality Control, University of Zagreb, Pierottijeva 6, 10000 Zagreb, Croatia

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

•Whether there is a significant difference in sweetness of these two yoghurts when adding fruit base containing artificial sweeteninig agent respectively containing sugar

•Whether panel sensory evaluation of fruit yoghurts conducted by a panel can be compared with results obtained by using electronic tongue analysis

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

Fruit yoghurts with addition of fruit base containing artificial sweetening agent are significatly sweeter than those with addition of fruit base containing sugar

Aroma intensity of yoghurts rises with the mass content of the added fruit base Electronic tongue analysis grouped yoghurt samples

according 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.

Sensory evaluationSensory evaluationPanel sensory evaluation

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 analysisAlpha 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).

Milk Hydrolysis

1. Adding MAXI LACT® L 2000 (Gist-Brocades GmbH, Germany)

2. Stirring f or 20 h at 6°C

Milk

Pasteurization

Cooling down to 43°C

I nnoculation with BT-10X and 100F

(DSM Food specialties, Netherlands)

I ncubation

Cooling down to 20°C at pH=4,6

Adding 1%, 5% or 10% of f ruit base

with sugar/ artifi cial sweetening agentHydrolized milk

f ruit yoghurtNon-Hydrolized

milk f ruit yoghurt

Yoghurt productionYoghurt production

•Comparing mean values obtained by results from Multisample comparison

tests among non 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.

•Comparison of mean values among all 12 yoghurt samples showed that

hydrolized milk 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

yoghurt samples containing fruit base with artificial sweetening agent.

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.

•B- yoghurt from nonhydrolized milk

•BD – yoghurts from hydrolized milk

•Indexses 1, 5, 10 – amount of fruit base in %

Picture 2. PCA analysis of yoghurts with fruit base containing artificial sweetening agent

Picture 1 Alpha MOS Astree electronic tongue

IntroductionIntroduction

ObjectivesObjectives

MethodsMethods

ResultsResults