| Cured fish is a very important traditional fermented food in China .It has some characteristics,such as a unique and strong cured flavor,a close texture,a bright colour and so on,it also has a large consumer market in China and southeast Asia. But cured fish supplied to the market is still manufactured by the traditional home-based production model, so this makes product quality unstable and there are many edible safe hidden troubles in the product. Traditional cured fish mainly depends on natural fermentation, which is under high salt concentration and depends on the growth and multiplication of beneficial microorganisms from raw material or environment to ferment and promote the typical flavor to form. It is very hard to control product quality, which is especially influced by the weather and season during natural fermentation , so products have large randomness and otherness. Traditional cured fish is usually used more than 10% salt to process , because high salt concentration could restrain harmful microorganisms and extended shelf-life.But traditional products taste so tough and salty,and also high salt food is not good for health . In order to satisfy the request of high-quality cured fish from consumers, it is necessary to discuss the process and mechanism of cured fish quality's formation theoretically and isolate and identify the microorganism of productive process to make sure their species and growth characteristic . Then proliferous dominant microorganism is vaccinated to production of cured fish to reduce dosage of salt,promote formatation of flavor,improve product safety and achieve the aim of improving traditional production technology and completing quality evaluation system.25 bacterial strains are isolated from traditional cured fish by differential medium , according to results of physiological and biochemical experiments,properties of strains are examined.4 dominant strains(L2,L6,L8,L11) are identified, L2 is Lb.casei subsp.casei, L6 is Lb.delbrueckii subsp. bulgaricus , L8 is Lb.farciminis and L11 is Lb. delbrueckii subsp.lactis.Fermentation characteristics of 4 dominant strains are tested . 4 dominant strains all have good ability of growing and producing acid at 30℃and they could also tolerate 8% salt and grow well . 4 dominant strains grow most actively at 35℃. Except L6 has the ablity of protease,the other 3 strains don't have the ablity of protease.4 dominant strains don't have the ablity of lipase, but they all could restrain the growth of E.coli and Staphylococcus aureus.Based on the result of single-factor experiment, it is found that low salt concentration and high cured temperature could increase total number of bacteria,which lead to the rise of free amino acid,TVB-N and peroxide value. According to the result of single-factor experiment, the optimum DVS(Direct Vat Set)cured technology with orthogonal experiment design is confirmed as follows: the inoculation amount of composite strains (Lb.casei subsp.casei:Lb.farciminis:Lb.delbrueckii subsp.lactis=1:1:1) is 106cfu/g, salt concentration is 5%, cured temperature is 10℃and cured time is 4 days. Cured fish produced under this technology has a better safe and organoleptic quality than traditionnnal cured fish. Direct vat set cured fish has a better safe and organoleptic quality than traditionnnal cured fish not only during the salted process but also during the drying process.Moisture of cured fish could be lower than 40% at 50℃dried 24h by hot air, cured fish dried at this temperature has better not only flavor and texture but also safe quality than natural air dried cured fish . |
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