Study On The Isolation, Screening And Application Of Enterococcus From Cantonese Sausage

Cantonese sausage is popular with Chinese people as one of excellent Chinese traditional meat products. The studies about Cantonese sausage gradually increase because more and more attention is paid to the quality, safety and modern machining technology of traditional meat products. But there is still a lack of information about the microbial characteristics of Cantonese sausage. In this thesis, excellent enterococcus starter cultures were separated from Cantonese sausage and the change and function of enterococcus in Cantonese sausage during heating process and storage were studied, aim to improve the safety and qulity of Cantonese sausage and offer foundation to the industrialization of Cantonese sausage.Firstly, the microbial characterization of 5 Cantonese sausage samples from 5 different producers was analyzed. The result showed that lactic acid bacteria was one of the predominant microorganism with a range of 1.24-5.03 log CFU/g. Enterococcus as one kind of lactic acid bacteria was found in all the sausage samples.Sixty strains were selected from Cantonese sausage using selective culture medium. Five strains which were G+, H2O2 enzyme negative, resistanted to the 6% NaCl and 150mg/kg NaNO2, did not produce gas, H2S, slime, H2O2, amino acid decarboxylase were selected.Two strains AD4 and AD8 which had strong ability of producing acid were finally selected and were identified as Enterococcus faceium for the first time from Cantonese sausage. The two strains can endure NaCl and NaNO2 well, have strong acidifying ability in high temperature, grow fast and proper concentrations of NaCl and NaNO2 can promote the growth of strains. The two enterococcus strains were suitable to apply to the fermentation of Cantonese sausage. E. faceium AD4 and E. faceium AD8 were inoculated into Cantonese sausage to investigate the microbial and physical-chemical characterization. The results showed that: by the end of the heating process, the number of staphylococci/micrococci in the three kind of sausages were 3.91 log CFU/g, 5.43 log CFU/g, 4.42 log CFU/g; the pH were 6.11, 6.00, 5.89 and the contents of titratable acidity were 5.56%, 5.97%, 5.99% showing that E. faceium AD4 and E. faceium AD8 can increase the number of staphylococci/micrococci, decrease the pH and increase the contents of titratable acidity.The two strains can improve the hydrolyzation of peptide as the proportion of the peptide with molecular weight above 10000 Da in the three kind of sausages were 33.56%, 27.15%, 28.14%.In this thesis, further investigation was conducted to study the function of E. faceium AD4 and E. faceium AD8 on the microbial and physical-chemical characterization of Cantonese sausage during storage. The results showed that:during the storage the counts of microorganism were further decreased while the pH was stable, the content of titratable acidity increased and the contents of NaNO2 reduced. After 150d's storage, the content of titratable acidity were 7.46%, 8.11%, 8.73% and NaNO2 were 11.52 mg/kg, 10.19 mg/kg, 10.24 mg/kg. The acid value in sausages inoculated enterococcus were higher than no- inoculated sausage.