Study On Analysis, Evaluation And Protection Technique System Of Volatile Flavor In Raw Milk

Focused on milk volatile flavor analysis, evaluation and protection technique, preparatory method and condition for using liquide-liquide extraction(LLE),static headspace(SH),solid-phase microextraction(SPME),purge and trap(PT) were screened and PT-GC/MS was used to analysis volatile compounds in raw milk for qualitative and quantitative evaluation. Sensory or flavor intensity evaluation in raw milk samples taking from different feeding conditions was carried out. According to the influencing factors and collected relevant information, HACCP(Hazard Analysis and Critical Control Point) system for protecting the flavor in raw milk was established. The main results are as follows:1 It was found that PT preparatory method was simple and able to extract most volatile compounds in raw milk with higher sensitive compared with LLE,SH,SPME.2 Based on single-factor analysis and orthogonal experiment design, the optimum conditions were at 40℃for 30min after saturating the samples with 0.32g/mL sodium chloride salt. The order of the factors influencing flavor extraction was time>temperature>Nacl.3 Under the optimized conditions for using PT-GC/MS to detect volatile compounds in the raw milk, it was found that alcohols, phenols, aldehydes, ketones and alkanes were the main compounds, which gave the unique flavor of raw milk.4 In the samples taken from the feeding conditions, there were no significant differences in the milk composition (P>0.05), but milk volatile flavor compounds was different both in level and components species in the raw milk. Dimethyl sulfide, aldehydes and ketones were significant differences on contents(P<0.05); Same acids was detected from the milk samples collected from mid size farms compared with family run farms and large size farms.5 For the milk samples taken from the feeding conditions, sensory scores were more than 9 points, but salty bitterness, flavor caused by feeds, cow body and cowshed were much lower for large size farms, them results for flavor intensity and sensory evaluation had positive correlation and dimethyl sulfide,3-methyl butanal,2-methyl butanal,benzeneacetaldehyde had larger contribution to the milk flavor.6 If storage and transport temperature was too high or keeping time too long,hand milking,milk exposure to poor rearing environment for long time had an impact on milk quality and flavor.7 According to the factors influencing in raw milk and other information, a HACCP system was established to protect the flavor of raw milk.8 After the implementation of the system, there were no significantly differences in milk composition (P>0.05), but total number of bacteria in the milk were significantly lower than control (P<0.05), milk yields were significantly higher than control (P<0.05), and all of the indicators were more stable than control. According to sensory evaluation scores and flavor intensity index, raw milk flavor were different at different sampling points. In conclusion, The HACCP system can maintain not only good flavor, but also improve good milk production.