大连海关技术中心

In this study,the inhibitory effect of phenyllactic acid(PLA)on Vibrio vulnificus biofilm formation at sub-inhibitory concentration was studied.Firstly,the biofilm model of V.vulnificus was established.Then the inhibitory effect of PLA on the formation mass and metabolic activity of V.vulnificus biofilm was analyzed using crystal violet staining method and XTT reduction assay.Using extracellular polysaccharides,extracellular proteins,and extracellular DNA as indicators,the effect of PLA on the extracellular polymers of V.vulnificus was evaluated.The effect of PLA on the structure of V.vulnificus biofilm was investigated by optical microscopy and laser confocal microscopy.The results showed that the aggregation,maturation and shedding periods of V.vulnificus biofilm were at 16～32,32～56,and 56～72 h,respectively.PLA at 0.5 MIC inhibited the biofilm of V.vulnificus in the maturation stage better,and the inhibition rates of biofilm formation mass,metabolic activity,extracellular polysaccharides,extracellular proteins,and extracellular DNA were 51.04％ ,33.62％ ,61.97％ ,32.70％ ,and 52.25％ ,respectively.Additionally,PLA disrupted the density and integrity of V.vulnificus biofilms,resulting in a dispersed distribution of bacteria.Therefore,PLA inhibited the biofilm formation of V.vulnificus by reducing the formation of extracellular polymers.This study provides a theoretical basis for the control of V.vulnificus biofilm in aquatic products.

In this study,salt-tolerant lactic acid bacteria were isolated and screened from traditional pickled vegetables of Northeast using the calcium solubilizing circle method and salt-tolerance performance analysis,the screened strains were identified using morphological observation,physiological and biochemical tests and 16S rRNA sequencing analysis,and the fermentation characteristics of the salt-tolerant lactic acid bacteria were further evaluated by determining the ability of the strains in acid production,nitrite degradation,antioxidant,bacteriostatic,aroma production and β-glucosi-dase production,and so on.The results showed that 6 strains of lactic acid bacteria were isolated from 7 pickled vegetables.Among them,the strains GNL2 and GNL3 with good salt tolerance could grow well under the conditions of 16％NaCl,and both of them were identified as Lactiplantibacillus plantarum.Compared with the strain GNL2,the strain GNL3 had better fermentation characteristics,with better acid-producing properties,the pH of fermentation broth was 3.75,the nitrite degradation rate was 99.73％,the β-glucosidase activity was 0.75 U/ml,the scavenging rate of 1,1-diphenyl-2-picrylhydrazyl(DPPH)radical of the intact cellular extracts was 80.60％,the scavenging rate of superoxide anion radical of cell-free extract was 78.70％,and the synthesis capacity of butanedione and acetaldehyde was 11.13 mg/L and 16.02 mg/L,respectively.The results indicated that the strain GNL3 could be applied in the production of traditional pickled vegetables in Northeast,and it could provide a high-quality bacterial resource for the realization of high-quality and large-scale production of traditional pickled vegetables.

Objective To ensure the accuracy of the results in such products,the uncertainty of the aerobic plate count in the plant-derived foods was evaluated.Methods In accordance with the national standards for food safety GB 4789.2-2022,the aerobic plate count in plant-derived foods was determined by plate count agar medium and test sheets.The introduced uncertainty components in the experiments were evaluated until the synthetic uncertainties of the aerobic plate count in the plant-derived foods on plate count agar medium and test sheets were calculated respectively.Results As the confidence probability was 95％,the extended uncertainties of the aerobic plate count in the plant-derived foods on plate counte agar medium and test sheets were 0.045 863 and 0.049 436,respectively.And the confidence intervals of the measurement result were 7.0×103-1.1×104 and 7.0×103-1.2×104 CFU/g.Conclusion The uncertainties of the aerobic plate count in the plant-derived foods on plate count agar medium and test sheets have no significant difference between them.According to the evaluation data,the results of the test samples can be judged and analyzed.It is suggested to improve in-house detection ability to reduce the introduction of uncertainty.It will provide strong technical support to production,inspection and supervision of the plant-derived foods.