Degradation Of Nitrosamines In Harbin Dry Sausages By Microbial Fermentation

Sodium nitrite is the key ingredient during meat curing because it can contribute to not only the colour formation of cured-meat, but also the specific flave, and delay the development of oxidative rancidity, inhibit the growth and toxin production of unwanted bacteria, particularly Clostridium botulinum, thus shelf life of meat will be prolonged. However, N-nitrosamines are classically produced by the reaction between sodium nitrite and secondary amine, and some of them have carcinogenic, teratogenic and mutagenic activity. In addition, N-nitrosamines can also be produced in the stomach by residual nitrite of cured-meat. In terms of the harm of N-nitrosamines, the most effective and reliable way is to reduce the residual nitrite in meat, and then make the formation of N-nitrosamines less likely.It is a brand new area of research that restraining N-nitrosamines formation by microbial fermentation. In this study, the microorganisms were applied into dry fermented sausages to measure the dynamic changes of nitrosamines in dry fermented sausage during the fermented process and changes of p Hysico-chemical properties were also studied. Detailed research content and conclusion are as follows:1. The bacterial strains that can degrade nitrosamines were selected in model systems. The study indicated that most of nitrosamines were decreased by Lactobacillus curvatus、Lactobacillus pentosus、Lactobacillus acidop Hilus and Lactobacillus sake,significantly(P < 0.05).2. The study mainly investigated the influence of Lactobacillus curvatus、Lactobacillus pentosus、and Lactobacillus sake on nitrosamine degradation and p Hysico-chemical properties of dry fermented sausages during fermentation. The three kinds of lactobacillus were respectively inoculated to Harbin dry sausages with the inoculum concentration at 107 CFU/g. The content of N-nitrosodiethylamine(NDEA), N-Nitrosodipropylamine(NDPA), N-nitrosodip Henylamine(NDp HA) and N-Nitrosopiperidine(NPIP), as well as the count of lactobacillus, p H value, water activity(Aw), nitrite residual amounts, thiobarbituric acid-reacitive substances(TBARS) and total volatile basic nitrogen(TVB-N) of dry fermented sausages during of fermentation at 0, 3, 6, and 9 d were determined. The results showed that Lactobacillus curvatus could significantly decrease the content of NDEA, NDPA, NDp HA and NPIP(P < 0.05) during the whole fermentation.,and had more effective on inhibiting the NDPA than other kinds of nitrosoamines(P < 0.05). At the 9th d, Lactobacillus pentosus had less effective on inhibiting the NDEA and NPIP(P >0.05),and yet Lactobacillus sake to NDPA and NDp HA.In addition, with the increased fermentation time, the lactobacillus count significantly increased(P < 0.05), and p H value, Aw, residual nitrite, TVB-N decreased(P < 0.05), and TBARS had no markedly changes(P > 0.05). The results revealed that Lactobacillus curvatus could significantly reduce the generation of nitrosoamines during fermentation process of Harbin dry sausages, and improve its overall quality.3. The effect of different inoculum levels of Lactobacillus curvatus on nitrosoamines in dry fermented sausages. Lactobacillus curvatus was applied for dry fermented sausages with 106 CFU/g and 107 CFU/g, respectively, and NDEA, NDPA, NDp HA and NPIP during of fermentation at 0, 3, 6, and 9 d were determined.It turned out that when the inoculum amount of Lactobacillus curvatus was 107 CFU/g, the content of NDp HA and NPIP significantly decrease(P < 0.05), while the inhibition to NDEA and NDPA was not significant; moreover, p H value, water content and Aw decreased.However, residual nitrite and TVB-N had little difference from dry fermented sausages with 106 CFU/g Lactobacillus curvatus.4. Lactobacillus curvatus and Stap Hylococcus xylosus were mixed as composite starters at different ratios for the fermentation of dry sausages. The results showed that dry fermented sausages with 106 CFU/g and 107 CFU/g Stap Hylococcus xylosus had rarely significant controlling effect on NDEA, NDPA, NDp HA and NPIP(P > 0.05),so dose p Hysico-chemical properties. The overall acceptability showed the sausage samples treated with composite starter culture had higher mark, because Stap Hylococcus xylosus could be conducive to the flavor.