Mechanism Of Reducing N-dimethylnitrosamine By Lactobacillus Pentosus R3 And Its Application In Fermented Sausages

N-dimethylnitrosamine(NDMA)is a widespread carcinogen in fermented meat products,and its reduction is beneficial to enhance product safety.In recent years,lactic acid bacteria(LAB)have been found to have the ability to decrease NDMA.However,the mechanism of NDMA reduction is not clear because of the complexity of meat products system and the diversity of factors affecting NDMA production.In addition,the reduction effects of LAB on NDMA in fermented sausage production,cooking and digestion are also obscure.In this study,the mechanism of NDMA reduction by Lactobacillus pentosus R3,which was chosen from the group's previous selection,was investigated by constructing a model system.Simultaneously,the effects of the strain on NDMA reduction during fermented sausage production,cooking and simulated digestion were studied.The results showed that:(1)L.pentosus R3 reduced NDMA content in the model system mainly via three pathways:direct degradation,reduction of its precursors(dimethylamine and putrescine)and inhibition of the formation.The strain was found to have good antioxidant capacities,which may contribute to the inhibition of NDMA formation.The results of cell proliferation and cytotoxicity assays showed that the genotoxicity of NDMA was reduced after treatment with L.pentosus R3.(2)L.pentosus R3 was found to grow well during sausage fermentation and ripening process,and significantly reduced NDMA and its precursors(P<0.05).Meanwhile,this strain inhibited the oxidation of protein and fat and reduced the a_w and p H of the sausages(P<0.05).L.pentosus R3 was also found to have a reducing effect on NDMA during the cooking stage of the sausage(P<0.05).This may be due to the fact that the strain reduced the content of NDMA precursors during the sausage production and inhibited its formation during the cooking process.(3)After digestion of the fermented sausages in the simulated gastrointestinal juice,the LAB counts,nitrite and dimethylamine content were significantly decreased(P<0.05),while putrescine and NDMA content were significantly increased(P<0.05).These results indicated that the reduction of NDMA precursors during digestion process promoted the formation of NDMA.Compared with the control,L.pentosus R3 can significantly reduce the content of NDMA(P<0.05).Meanwhile,the strain had a reduction effect on the precursors of NDMA.After the digestion in simulated gastric juice,the strain partially survived and retained a certain amount of antioxidant activity,and the simulated intestinal juice treatment had no significant effect(P>0.05).In simulated gastric juice,L.pentosus R3 reduced the content of putrescine and DMA(P<0.05),while in simulated intestinal juice it reduced the content of NDMA.The results showed that the main ways of reducing NDMA in fermented sausages by L.pentosus R3 in simulated digestion included reducing the precursors(gastric juice digestion),direct degradation(intestinal juice digestion)and antioxidant function.