Use of stevia in yoghurt technology
Authors: Musiy L. Y. , Tsisaryk O. Y. , Slyvka I. M. , Jeremica N. 
Published: December 2020

The purpose of the work was to develop technology, investigate the properties and quality indicators of yogurt using stevia extract. Experimental studies of organoleptic, physicochemical and microbiological parameters of yogurt were conducted in the laboratory of the milk and milk products technology department. At the first stage, yogurt formulations were developed using different amounts of stevia extract, namely 0.1 %, 0.2 %, 0.5 %, 1.0 % by weight of the normalized mixture. The yogurt with the sugar addition 5.0 % of weight of the normalized mixture was the control sample. The aqueous extract of stevia was prepared as follows: 30 g of crushed dry raw material was poured into 250 ml of hot water and extracted in a flask under reflux in a boiling water bath for 30 minutes. The aqueous extract was filtered through a paper filter and evaporated to 100 ml. The obtained extract was used for further studies. Yogurt was made by thermostatic method. Bacterial preparation of direct application of FD DVS ABY-3 was added to the milk mixture cooled to a temperature of (37 ± 1) ºС. After stirring, sugar and stevia extract were added to the normalized mixture in the calculated amount. The mixture was stirred and packed in a glass container. After adding all the components, the mixture was fermented at a temperature of (37 ± 1) ºC. After fermentation the product was immediately cooled to a temperature of (4 ± 2) ºC in a refrigerator, and then sent for storage for 21 days. In fermented samples of yogurt during fermentation, the activity of acid formation was determined by changing the active and titrated acidity. The titratable acidity was determined according to GOST 3624-92 “Milk and dairy products. Titrometric methods for determining acidity”. Measurements of active acidity were performed using an electronic pH meter “Muttler Toledo MP220”. Organoleptic and physicochemical parameters were investigated in the finished product according to DSTU 4343:2004 “Yogurts. General technical conditions”. Microbiological parameters of yogurt with stevia extract during storage were examined on the 1, 7, 14 and 21st day according to DSTU IDF 117B:2003 “Yogurt. Determination of the number of characteristic microorganisms. The method of counting colonies at a temperature of 37 °C”. Experimentally it was found that the highest titrated (84 °T) and lowest active acidity (4.39 pH units) characterized for the sample with the addition of 1.0 % stevia extract. Yogurt obtained by adding stevia extract in the amount of 0.5 % was optimal for organoleptic characteristics. During storage of yogurt samples, the highest value of titratable acidity was observed in the control, which is explained by the maximum content of lactobacilli cells, but its organoleptic characteristics deteriorated. Determination of the number of viable lactobacilli cells in yogurt samples confirmed the assumption that their more active development was in the control and samples using 0.1 % stevia extract, which correlates with titrated acidity. For the production of yogurt with good organoleptic characteristics and probiotic properties, we propose to use in its technology 0.5 % stevia extract, as well as fermentation culture of direct application ABY-3 (Chr. Hansen). The use of stevia in the production of yogurt not only has a positive effect on the energy composition of the product, but improves organoleptic characteristics. Thus, there is possible to manufacture of the product in order to expand the range of dairy products available to people with diabetes, obesity and other diseases which involves reducing or completely eliminating sugar from your daily diet.