Determination of effect of ice cream mixes with different pH values and production methods on physicochemical,microbiological and sensorial properties of kefir icecream

In this study, kefir ice creams were produced at 3 different pH values (pH 5.5, 5.8 and 6.1) and by 2 different methods (fermenting ice cream mixes with kefir starter culture and mixing ice cream with kefir at certain ratios). The control group of the study was ice cream obtained by processing of ice cream mix, which is not inoculated with kefir starter culture or without addition of kefir . The ice cream mixes were used in the production fat free milk solids contained 10% milk solids-not-fat, 18% sugar , 3% fat and 0.5% stabilizer. In the production of kefir ice creams by the first method, the ice cream mix was heated at to 75°C for 5 minutes, cooled to 4°C and aged at 4°C for 24 hours. After ageing process, the ice cream mixes were heated to 25°C, inoculated with kefir starter culture and fermented at 25°C until the pH values were 5.5, 5.8 and 6.1. When the fermentation process was complete, the ice cream mix was processed to obtain ice cream. According to the second method, the ice cream mixes heated at 75°C for 5 minutes was cooled to 4°C and aged at 4°C for 24 hours. After ageing process, the ice cream mixes were heated to 25°C. Kefir produced for use in the production of ice cream was stored at 4°C for 24 hours and then heated to 25°C. Ice cream mix and kefir were mixed with pH values of 5.5, 5.8 and 6.1. All samples were stored in 200 g plastic packages at -20°C for 90 days. The physicochemical, microbiological and sensory properties of ice cream samples were dinvestigated on days 1, 45 and 90 of storage. When evaluated with respect to physicochemical properties of of ice cream mixes, the effect of pH value of ice cream mix and production methods on pH, titratable acidity and viscosity values on ice cream mixes were found to be significant at the P<0.001 level. Total solids, ash and fat contents of ice cream samples were determined to be ranging from 30.81% to 31.81%, from 0.76% to 0.80%, and from 2.85% to 3.00%, respectively. The protein and total sugar contents of the ice cream samples varied from 4.55 to 4.75% and from 22.50 to 23.47%, respectively. It was determined that the effect of pH value of the ice cream mix, production method and storage time on the overrun, hardness and melting values of ice cream samples was significant at the level of P<0.001. It was determined that the average total mesophilic aerobic bacteria, lactobacilli, lactococci, acetic acid bacteria, leukonostoc and yeast counts were 9.34, 9.33, 9.35, 9.26, 6.97 and 2.51 log cfu / g respectively in kefir samples and as a result of the microbiological analysis, yeast and bacterial counts of kefir samples were consistent with iv the literature. According to the statistical evaluation of result of microbiological analysis, the effect of pH value of the ice cream mix, production method and storage time on the microbiological properties of kefir ice cream samples was significant at the P<0.001 level. The sensory characteristics of the kefir ice creams and the control ice cream samples were evaluated in terms of aroma, color and appearance as well as structure and textural properties of the ice creams. As a result of the evaluation, the effect of the pH value of the ice cream mix, production method and storage time on the aroma of ice creams was not significant (P>0.05) and only the effect of storage time on the color and appearance characteristics and structure and texture properties of ice creams was significant respectively at the P<0.001 and P<0.05 level.