Study On The Regulation And Control Teochnology For The Taste Characteristics Of Fermented Milk

The flavor of fermented milk is the key factor for consumer choice. Acid-sugar ratio is an inportant index of effecting the quality of the taste of fermented milk. In order to improve the quality of fermented milk, the acid production performance of different lactic acid bacteria and the optimization of fermentation process was studied. Additionally, the effect of different sweeteners on the taste quality of fermented milk and the control technology for the characteristic taste of critical control points was also studied. The main conclusions are as follows:Titratable acidity, viable counts of lactic acid bacteria, organic acids were analyzed to as standard to study the performance of acid production of 4 strains of lactic acid bacteria. The results showed that Lactobacillus acidophilus and Lactobacillus casei could grow rapidly in fermented milk, which promoted the fermentation process of fermented milk. Lactobacillus plantarum and Lactobacillus casei almost had no growth in fermented milk with little effect on the fermentation of fermented milk. The post-acidification of fermented milk with Lactobacillus acidophilus is weak, while the phenomenon of samples with Lactobacillus casei was opposite. The types and contents of organic acids in fermented milk was analyzed by high performance liquid chromatography (HPLC). Formic acid, malic acid, lactic acid,acetic acid and citric acid were quantitatively analyzed. Lactic acid was found to be the most abundant organic acid in all samples.The fermentation conditions of Lactobacillus acidophilus and starter were optimized,The quality of Lactobacillus acidophilus fermented milk was studied by sensory evaluation.The overall quality of Lactobacillus acidophilus was studied by sensory evaluation.Optimization of fermentation conditions by response surface are as follows: the traditional fermentation agent : Lactobacillus acidophilus - 2:1, fermentation temperature was 41.8℃,inoculum concentration was 3%, the fermentation time was 4.50h under this condition. The sensory quality of fermented milk produced under this conditions was with typical fermented milk aroma and its quality was stable in the cold storage period. The score of sweet taste for fermented milk was the lowest among all sensory indexes, which indicated that it is necessary to control the taste characteristics of fermented milk.Sensory evaluation was used to evaluate the effects of different sweeteners on fermented milk. The results showed that honey could reconcile the flavor of fermented milk and increase the special honey aroma. The changes of lactose, sucrose, glucose, fructose and organic acid in fermented milk with different sweeteners were analyzed by HPLC. The results showed that the glucose and fructose in samples with honey can be used by start cultures, and can increase the citric acid content in fermented milk. The influence of different honeys on the flavor of fermented milk was analyzed by gas chromatographic mass spectrometry (GC-MS) and sensory evaluation. The results showed that honey could improve the taste quality of fermented milk and increase the type and content of aroma compounds in fermented milk.The critical control points in the production process of fermented milk was confirmed,including raw materials, sterilization, fermentation and ripening. The sensory evaluation,titratable acidity, sugar and acidity ratio of key control points were analyzed. The quality control system of different critical control points was verified by double-blind samples. The results showed that the control system was accurate and reliable.