FERMENTATION OF YOGHURT WITH DIFFERENT CONCENTRATIONS OF MILK POWDER, SWEETENED WITH Stevia rebaudiana AND FLAVORED WITH VANILLA ESSENCE.

The consumption of yoghurts always been very great all over the world, since its development, however in the last years has increased in the Brazilian and worldwide markets, due to its high nutritional quality with ideal amounts of protein, calcium, vitamins, especially those of the B complex and minerals. Because of this fact, the food industry has increasingly brought innovative milk and dairy products to the supermarkets shelves. This research aims to compare the fermentation of five formulations of yoghurt with different concentrations of milk powder. All formulations contained the same ingredients, except for the different concentrations of powdered milk. It was used the starter culture Yoflex, 0.15% of Stevia rebaudiana and 0.05% of vanilla flavor essence. In formulation 1 (F1) was used 15% of reconstituted skim milk powder, F2 was reconstituted with 20% milk powder, F3 with 25% milk powder, F4 30% and F5 with 35% milk powder. All formulations were pasteurized at 65 ° C/30 minutes, cooled to 42 °C, then the starter culture was added. The formulations were conducted at this temperature. Different degrees of acidity were observed for the five formulations. F1 reached final acidity of 80 ºD, F2 90 ºD, F3 100 ºD, F4 90 ºD and F5 90 ºD. It is possible to conclude that the different concentrations of milk powder influenced the fermentation time of the formulations, whereas F1, F2, F3 and F4 took longer than expected to reach the desired pH, F5 did not reach this value even after 6h fermentation. However, using higher amounts of milk powder, we observed an influence in the final acidity and pH of the yoghurts. The pH evolution was evaluated every 30 min until reaching the final pH of 4.6. In F1 a linear decrease in pH was observed, reaching 4.40, as well as in F2 pH 4.42, F3 reached a pH of 4.47, and F4 pH 4.65 after 5 h of fermentation. To F5, even after 6 h of fermentation, the final pH was 4.8, above the target pH. This is a preliminary step, it is necessary to develop new tests as well as sensory analysis with more panelists.