| Biogenic amines(BAs)are easily produced and accumulated during sausage fermentation,which is very likely to produce food safety hazards.Previous studies found that nisin and Lactobacillus plantarum(LP)can effectively control the content of BAs in fermented sausages.In this study,Tremella fuciformis polysaccharide(TFP)was used as a wall material to encapsulate nisin to form nisin/TFP nanoparticles(NTNs).Then,NTNs and LP were grafted by 1-(3-dimethylaminopropyl)-3-ethylcarbodiimide hydrochloride(EDC)and hydroxysuccinimide(NHS)catalysts according to a certain mass ratio(3:1,2:1,1:1,1:2,1:3)to form NTN@LP.Finally,NTN@LP was added to the fermented sausage to study its effect on the content of BAs in fermented sausage,and the effect of NTN@LP on microbial diversity in fermented sausage was also discussed,in order to lay the foundation for the study of the control mechanism of BAs content.The main research results are as follows:(1)By optimizing the preparation conditions of NTNs,it was found that the optimal preparation condition was p H 4.Under this condition,the average particle size of NTNs was 227 ± 20 nm,the zeta potential of NTNs was 16.74 ± 1.14 m V,and the entrapment rate of NTNs was 86 ± 1.16%.(2)The optimized NTNs and LP were grafted into NTN@LP by EDC/ NHS.It was found that when the ratio of NTNs to LP was 2: 1,the grafting rate of NTN@LP was the highest(68.8 ±2.1%),and the living rate was 85.6 ±2.11%.When the p H value is 4.0,5.0,6.0,nisin in NTN@LP can be released continuously for 16 d.Hemolysis test and in vitro cytotoxicity test showed that NTN@LP had no hemolysis and no toxicity to human embryonic kidney cells,so it could be safely used in food.(3)NTN@LP could improve the quality of sausages during fermentation.On the 7th day,the TBARS values of sausages inoculated with LP and five different NTN@LP decreased by 20.65%,26.08%,30.43%,40.21%,35.87% and 38.04%,respectively,compared with the CK group.NTN@LP has a strong inhibitory effect on tyramine and histamine,and can also control the content of other BAs to some extent.On the 7th day,tyramine in pure LP group was 38.25% lower than that in CK group(p < 0.05).Tyramine in NTN@LP group(2:1),which had the best inhibitory effect,was 78.16% lower than that in CK group(p<0.05).Microbial diversity analysis showed that Firmicutes accounted for about 83% and Proteobacteria accounted for about 16% in the NTNLP group,which were between the Blank group and the NTN group,indicating that the addition of NTN@LP changed the bacterial composition of the sausages to some extent.In fermented sausages,a total of 5 phyla and 15 genera of microorganisms were identified.Among them,based on the phylum level,the dominant bacteria were Firmicutes;Based on the genus level,the dominant bacteria were Lactobacillus.The results of the relationship between samples and species showed that the species abundance of each group was in the following order: Blank group > NTNLP group > NTN group. |
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