Study On The Storage Properties Of Cololabis Saira And Its Lightly Preserved Product

As one kind of the important economy fishery resources,Cololabis saira has the characteristics of higher fat and protein content and favored by consumers.Changes of biochemical indexes,microbial indexes as well as sensory scores of Cololabis saira and it's lightly preserved products were measured in this paper.This research will provide technical reference for the fresh processing and high-value utilization of Cololabis saira.(1)To analyze the quality changes of Cololabis saira during refrigerated storage,sensory scores,TVB-N values,TBARS values,total bacteria counts,as well as electronic nose measurement signals of Cololabis saira under 4? storage condition were determined.High throughput sequencing technology based on Illumina was applied to investigate the changes in bacteria composition of Cololabis saira during refrigerated storage.Results showed that TVB-N value increased significantly(P<0.05)from the fifth day and got close to the limit of 30 mg/100 g on day 11.TBARS levels showed a rapid growth trend and caused rapid decline in odor scores.A rapid increase in total bacteria count was determined from the fifth day and got close to the limit of 7.0 Log10 CFU/g on day 11,which indicated the shelf life of Cololabis saira was within 9 to 11 days.Cluster distribution on the two-dimensional graphics of PCA was observed and samples with similar freshness are distributed closely.The research data discovered by high-throughput sequencing technology showed that the dominant bacteria belonged to Cololabis saira were Proteobacteria and Cyanobacteria in phylum level.Gammaproteobacteria and Pseudomonadaceae had strong adaptability to refrigerated storage,and the similar trends of the flora are also closer to the evolutionary relationship.(2)To analyze the effect of gutting on shelf life and corruption characteristic of Cololabis saira during 4±1? storage.Results showed that sensory scores of both two groups samples declined during refrigerated storage,and the downtrend of gutted samples were more obviously.TVB-N value indicated the shelf life of Cololabis saira lagged behind slightly than that of sensory scores.The treated samples got close to the limit of 30 mg/100 g on day 8,while the ungutted groups on day 12.The oxidation rate of fish lipids was accelerated by the gutting treatment,but the TBARS values of the two groups were not surpassed the limit of 5 mg/kg at the end of shelf life.The initial total bacterial count of the treated group was significantly higherthan that of the control group(P<0.05),which got the limit of 7.0 Log10 CFU/g on day 8,while the control group on day 10.The shelf-life of the complete state Cololabis saira were 10~12 days during refrigerated storage,and the gutted samples were about 8 days.(3)The processing technology of lightly preserved Cololabis saira products were determined: 10% salt solution(solid-liquid ratio 1:2)salting for 2 hours at 20?,and 40 ?hot air drying for 5 hours,then we got the lightly preserved products after vacuum packaging which hold 44.30±1.08% moisture content,Aw 0.895,3.17% NaCl.Technical analysis of the low-field nuclear magnetic resonance of salted and dried samples in the process of water distribution and combination were detected.Results showed that pickling treatment transformed part of the hydration water and free water into immobilized water.Hydration water relaxation time T21,immobilized water relaxation time T22 and free water relaxation time T23 were decreased during drying treatment.The nuclear magnetic resonance imaging(MRI)grayscale and pseudo color showed that drying treatment changed the water and oil balance of Coloabis saira,which was consistent with sensory evaluation.Considering sensory,physical,biochemical index,texture profile analysis(TPA),microbiological indicators and electronic nose components,the shelf life of lightly preserved Cololabis saira products was within 7 to 8 weeks.