Isolation And Identification Of The Proteinase And Lipase Producing Mould From Sichuan Sausage And Its Preliminary Study In Fermented Sausage

Fermented sausage is one of the fermented meat product with the largest yield in the world. Because of its nutrition, long shelf-life and special flavor, the fermented sausage is popular all over the world. In modern industrial processing, more attention are paid on starter cultures to achieve effective control and ensure safety and stable quality. Currently, the aim of our study is to obtain the predominant strains in the source of traditional fermented meat products and apply to the processing of fermented meat products.In this study, The predominant mould was sieved out from the traditional Sichuan sausage.These mould was mixed with the lactobacillus and staphylococcus which used during the processing of Sichuan sausage. The affection of mixed strains to the flavor of sausage was evaluated. The results provide a theory for the research of multiple starter cultures and the application of mixed starter cultures. The major researches content and experimental results are as follows:1. A total of121strains of moulds were isolated from the surface of Sichuan natural fermented sausage,which belonged to Aspergillus, Penicillium, Mucor. One strain of mold named P2with the highest protease and lipases activity has been isolated by primary and secondary screening. Based on the morphologic observation and molecular biology identification, P2was identified as Penicillium chrysogenum. The optimal temperature for its growth was24℃2. The toxicological properties of P.chrysogenum P2were carried out, including acute toxicity, bone marrow cell micronucleus, sperm shape aberration test, and30days feeding test. The LD50of the fermented product of Penicillium chrysogenum was more than10.0g/kg bw, which fell into the limit of non-toxidity. No difference was observed in the genetic toxicity test of bone marrow cell micronucleus, sperm shape abnormality test. Abnormal phenomena had not been found in30days feeding test under the experimental dosage with2.,5.0,10.0g/kg bw. Results indicated that Penicillium chrysogenum was a safe and non-toxic mould.3. A total of38volatile compounds were identified from P.chrysogenum in liquid glucose media, containing terpenes (84.741%) and alcohols (11.619%).38compounds were identified in liquid peptone media, including terpenes (30.052%) and akanes(58.420%).33volatile compounds were identified in liquid maize oil media, and the major components were consisted of terpenes(70.963%) and acids(20.208%).4. In order to better understand the function(s) of Penicillium chrysogenum P2in sausage fermentation, we have studied the physical, chemical and microbiological indicators of the sausages which prepared by nature fermentation and mixed fermentation with Penicillium chrysogenum P2, Lactobacillus pentosus L76and Saprophytic staphylococcus S25. The results showed that the pH of mixed fermentation sausages were remarkablely lower than nature one’s (P<0.05) during the whole process, and the water content and Aw of the sausages were decreased, however, after8days of air-dry the water content in mixed fermentation sausages was clearly lower than nature fermentation one’s. Beside that, the acidity value, peroxide value and amino acidic nitrogen of the sausages under both fermentation conditions were increasing day by day, but the amino acidic nitrogen was much higher in mixed fermentation sausages at first day of inoculation (P<0.01). During the30days of sausages mature process, the proteins had been hydrolyzed all the time, and4days after air-dry the protein hydrolyse value of mixed fermentation sausages was significantly higher than nature fermentation sausages (P<0.05). Furthermore, the number of bacterias, Lactobacillus, Staphylococcus, yeasts and moulds counts on mixed fermentation sausages were higher than nature fermentation sausages’ in the first13days of air-dry, nevertheless the results were totally opposite after that. Moreover, the color of the sausages were getting better with the extension of air-drying time but the shape of mixed fermentation sausages were better than nature one’s at first15days (P<0.05). At last, It was founded that the taste of mixed fermentation sausages were much better than nature fermentation sausages during30-day-mature process (P<0.05). Besides the relative content of alcohol esters, aldehydes and ketones in30-day-old sausages were obviously higher than fresh one, and they were also much higher in mixed fermentation sausages compared with nature fermentation sausages after30days air-dry(P<0.05).