| Kouwan Lao(KWL), a kind of Chinese traditional fermented dairy products, which is fermented by the mixture of rice wine and milk, has higher nutritional value. However, the production of KWL is always small handicrafts workshops, and the raw milk mostly used with HTLT(High Temperature Long Time sterilization) milk, low security, and the curd is poor. In order to solve these, we used different raw milk(added 3% skim milk powder in HTLT milk,pasteurized milk and UHT milk) for KWL making. We made a research on the effect of different raw milk on the microbial composition, physical and chemical properties, textural properties and microstructure of KWL, which provided a theoretical basis for the industrial production of KWL.Four kinds of JiuQu from marketed for KWL production were collected, and the optimal JiuQu was selected by analyzing the sensory characteristics of KWL and rennet activities of rice wine. KWL, made by four different raw milk, were labeled H,S,P and U. And based on JiuQu, rice wine, raw milk, curds and ripened KWL for studies, research applied 16 S r DNA V3 region and 26 S r DNA D1 region for PCR-DGGE analysis. While we used AOAC(Association of Official Analytical Chemists) standard methods to determine the physical and chemical properties, the Textural Profile Analysis(TPA) to determine the textural properties and scanning electronic microscopy(SEM) to observe the microstructure of ripened KWL and the sensory evaluation of Kouwan Lao.The results showed that:(1) Four kinds of KWL had rich bacteria as for fungi during the fermentation process. The dominant strain of JiuQu was Rhizopus oryzae, and Pediococcus pentosaceus, Wickerhamomyces anomalus were detected in the preparation of fermented glutinous rice fermentation. In the process of H KWL making, flora species changed a lot and there were many kinds of bacteria in HTLT milk, Enterococcus faecium, Lactobacillus brevis, Clavispora lusitaniae and Saccharomyces cerevisiae were detected in ripened KWL, which did not appear in the curd; In the process of S KWL making, we also detected Lactobacillus(Janthinobacterium sp.) and it was the dominant strain; In the process of P KWL making, the dominant strain was Lactobacillus casei, the strain was also presented in U KWL ripened period. There is almost no changes in microbial flora of curd and ripened period at S and P KWL, respectively. Rhizopus oryzae was detected in curd and ripened period of H KWL, as well as ripened period of S and U KWL. The dominant strains in HKWL was Pediococcus pentosaceus, which came from the starter; Similarly, U KWL dominant strains Wickerhamomyces anomalus also came from the starter; In the process of P KWL making,fungi was not detected.(2) KWL was made from four different raw milk, it’s composition analysis showed that,protein differences in four KWL groups were significant(p < 0.05), and P KWL had the highest protein and fat content. The difference about moisture content of H group was significant, and the content was the highest.(3) KWL texture(TPA) analysis, hardness, adhesiveness, springiness, cohesiveness,gumminess, chewiness and resilience of H group were lower than the other three groups, and the difference was significant(p < 0.05). Hardness and adhesiveness in S group were lower than P and U, and the difference was significant(p < 0.05). The hardness, adhesiveness, springiness in P and U group were the highest and the difference was significant(p < 0.05).(4) Microstructures of four groups KWL were observed using scanning electronic microscope,H Group, curd surface was rough. In S group, microstructure is uniform, smooth of surface with curd. In P group, the curd surface of P KWL was smooth and uniform. In U group, the curd surface was a little rough.Research results show that based on processing of KWL production by different milk, and combined the analysis of microbial community diversity and quality of products, the KWL made by pasteurized milk was considered to have the better texture, denser microstructure and the better sensory evaluation. |
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