Research On The Quality Of Reconstituded Yogurt With Milk Powder Which Is Made In Different Processing Conditions

Because of geographical constraints, and other factors, the growth cycle of raw milk production and processing, production and application of milk powder has been paid attention. Yogurt is a popular dairy products with a wide range of markets. Whether milk powder is sold directly or after reconstitution replace fresh milk as a raw material applied in yogurt, there are some flaws. Among them, the deterioration occurred during milk processing of oxidation flavor is the main reason to limit its consumption and applications. The purpose of this project is to study the processing of milk heat-related processes, including preheating, concentration, spray drying which affect flavor oxidation compounds(OFC) and texture of milk and yogurt, and study the influence of milk procession on the formation of oxidation flavor compounds and potential mechanism.Milk processing different heat-related processes to obtain the components of milk in a significant increase in the concentration of oxidized flavor compounds compared to raw milk, heat-treated 2, concentrate temperature 55℃, drying under 160℃sample obtained in 2-heptanone, 2,4-nonadienal, octanal contents were 711.63μg/kg, 34.11μg/kg, 274.51 μg/kg, compared to the other two drying temperature was the lowest concentration sample prepared. Higher concentration slipped out the enrichment process was oxidized flavor, indicating that flavor loss occurs while the enrichment process, and also severe lipid oxidation. DPPH· scavenging activity of milk powder reduces compared to raw milk,but the value of their POV increases. The significant changes in the heat treatment and flavor compounds exposure of raw milk which is caused by spray drying and evapraton concentration is incentives of oxidation flavor’s significantly increasing.Thermal processing of milk will reduce the concentration of Ca 2+ milk, particle size increases, the heat treatment process have a similar impact on typical texture parameters of reconstituted yogurt: the firmness and consisiter increase with the raising of heat treatment; index of viscosity and cohesive strength increases with the reduction heat treatment. The heat sterilization-2 process raw milk(pasteurized 75℃~85℃, 5s), and concentrated temperature 50℃, spray drying inlet temperature of 160 ℃ to obtain fermentation of yogurt highest water holding capacity(72.94%) recovery after milk, raw milk heat sterilization process 2(pasteurized75℃~85℃, 5s), and concentrated at a temperature of 55℃, Recoonstituded yogurt gel contraction coefficient which is made from milk of spray drying inlet temperature of 160℃ is lowest(33.13%).Incresing the heating intensity can change the content of the typical yogurt flavor. PCA forecasts on the flavor combination of variables showed that the increase of heat treatment intensity,and yogurt flavor associated with oxidation of aldehydes, methyl ketones, aldehydes have rising trend. Concentrated sectors have a greater impact on the recovery of yogurt flavor production. The yogurt sensory evaluation showed that the yogurt which is made from the reconstitute milk(pasteurized at 75℃~85℃ for 5s, concentrated at 55℃, spray drying inlet temperature at 160℃) has better texture and yogurt flavor.