| Crab paste is a salted raw aquatic product made from fresh Portunus crab by rinsing,shelling gills,cutting,adding a little salt,monosodium glutamate,liquor and other condiments.Crab paste has many advantages,such as rich nutrition,and delicious taste.It is a characteristic aquatic product in coastal areas of China,and is popular with local residents.However,because crab paste is eaten directly without being cooked and processed,there is a high potential risk of food safety,which seriously limits the promotion and development of this product.In this paper,the microbial flora structure of traditional pickled raw crab paste during low temperature and freezing storage was analyzed,and the dominant spoilage bacteria were identified.The microorganisms in crab paste processing and final products were controlled by reducing bacteria in raw materials,adding biological preservatives and establishing quality and safety control system.The main results were as follows:1:To analyze the microbial community structure of crab paste under different storage temperatures.Methods:16S rDNA,V1-V3,V3-V4 regions were sequenced by using Illumina MiSeq high-throughput sequencing technique,and OTU clustering,alpha diversity and species classification were performed’The results showed that:(1)18 and 26 genera of microorganisms were obtained from VI-V3 and V3-V4 of crab paste samples stored at-20℃for 3 days,and 16,19 genera were obtained from V1-V3 and V3-V4 of crab paste samples stored at 4oC for 3 days.respectively;(2)The main bacterial with relative abundance over 1%were as follows:Carnobacterium、Jeotgalibaca,Brochothrix,Staphylococcus,Psychrobacrer and Vibrio.(3)The dominant microflora of crab paste samples stored at-20℃ for 3 days were Carnobacterium(V1-V3,68.81%;V3-V4,69.29%)and Vibrio(V1-V3,16.75%;V3-V4,14.39%).(4)The dominant microflora of crab paste samples stored at 4℃ for 3 days were Carnobacterium(V1-V3,73.37%;V3-V4,70.35%),Jeotgalibaca(V1-V3,11.82%;V3-V4,12.35%)and Staphylococcus(V1-V3,5.45%;V3-V4,5.01%).2:The results of decontaminating treatment of raw materials showed that H2O2,NaCIO and ultrasonic cleaning all had significant(P<0.05)decontaminating effects.Among them,the decontaminating effect was NaClO>ultrasonic>H2O2,and with the increase of concentration and power,the decontaminating effect increased gradually.The total viable count(TVC)of raw materials can be reduced to 3.33±0.06 log10(cfu g-1)by NaClO combined with ultrasonic treatment,which is much lower than the limit of TVC<4.70 log10(cfu g-1)stipulated in national standard GB10136-2015.Further,the raw materials were treated by this condition and processed into crab paste,which was placed under the simulated production environment temperature(≤15℃).The TVC value of crab paste was 4.71±0.03 log10(cfu g-1)for 4 hours in the control group,which exceeded the national standard limit.The TVC value of crab paste was 4.68 ± 0.05 log10(cfu g-1)for 6 hours in the decontaminating treatment group,which was close to the national standard limit.Therefore,it is suggested that the actual processing time should be controlled within 4 hours.3:The effects of four biological preservatives on the quality of crab paste during storage were studied.After 12 months of storage,the TVC value of the control group without preservative was 4.78±0.01 log10(cfu g-1),which was significantly(P<0.05)higher than that of the 4.7 log10(cfu g-1)stipulated in the national standard.The TVC values of 0.05%Nisin,0.5%ε-polylysine,0.03%tea polyphenols and 0.1%citric acid treatment groups were 4.36±0.00、4.38±0.02、4.54±0.02、4.34±0.02 log10(cfu g-1),The results showed that the TVC of crab paste could be inhibited by four kinds of biological preservatives separately.L9(34)Orthogonal optimization test results showed that the four biological preservatives had synergistic bacteriostasis effect when used simultaneously.Considering the bacteriostasis effect and quality index,the best combination was A1B3C3D3(0.01%Nisin+0.04%ε-polylysine+0.03%tea polyphenol+0.1%citric acid).Under these conditions,TVC,pH value and the total volatile basic nitrogen(TVB-N)of crab paste were 4.28±0.03 log10(cfu g-1)、7.87±0.00、18.89±0.13 mg.100g-1 respectively,which were significantly(P<0.05)lower than the national standard limits,indicating that the shelf life of crab paste could reach one year.4:High throughput sequencing was used to analyze the micro flora of crab paste stored at-20℃ for 12 months.The results showed that more than 1%of the control group were Psychrobacter,Aliiroseovarius,Vibrio,P seudoalteromonas,Photobacterium and Pseudomonas,accounting for 60.25%、4.73%、3.83%、3.17%、2.95%and 1.58%respectively.The proportion of A1B3C3D3 in fresh-keeping agent group more than 1%were Psychrobacter、Photobacterium、Phenylobacterium、Psychrilyobacter、Aliiroseovarius、Pseudoalteromonas、Vibrio and Shewanella,accounting for 41.57%,15.32%,5.71%,1.85%,1.5%,1.28%,1.25%and 1.11%,respectively.Considering the phase and proportion of bacteria,the compound preservative has a significant(P<0.05)inhibitory effect on spoilage bacteria and pathogenic bacteria of crab paste,thus maintaining the quality of crab paste during storage.5:The crab paste processing technology was determined based on the HACCP principle and full investigation on the production site of the enterprise.According to the hazard analysis judgment tree,four key control points were determined,including acceptance of raw materials and supplementary materials,decontamination treatments,removing crab gills and metal detection.The key limits,monitoring procedures and corrective measures were formulated,and the whole quality control system of crab paste from acceptance of raw materials to packaging of finished products was constructed. |
PDF Full Text Request