Quality And Flavor Changes Of The Bighead Carp's Head During The Fresh Logistics Transportation

In this paper,the bighead carp's head during fresh logistics transportation was taken as the research object,and the microbial flora structure,flavor components and fatty acid composition of the carp head during transportation were explored by basic index determination,miseq high-throughput sequencing technology and gas chromatography-mass spectrometry.This could provide a theoretical basis for the quality changes of the bighead carp's head during fresh logistics transportation,and also could provide guidance for optimal fresh-keeping transportation time.(1)Taking the fish brain,and muscles near the eye,chin and incision as evaluated samples,changes in the quality of bighead carp's head during fresh logistics transportation was investigated by analyzing the pH values,total volatile basic nitrogen(TVB-N),2-thiobarbituric acid(TBA)values,total bacteria counts.Changes in the color and texture of muscle near the incision were also measured.The results demonstrated that during the 72 h simulated transportation,the temperature of bighead carp's rised slowly within 24 h,followed by fast increasing after 24 h of transportation.The pH values of above four parts decreased gradually,while the TBA values,TVB-N contents,and total bacteria counts increased linearly with prolonged time.The hardness,whiteness and brightness of the muscles near the incision decreased,but the yellowness increased.When the simulated transportation time was over 60 hours,liquid omited from fish head's obviously,the sensory quality reduced significantly,and strongly fishy flavour occurred.It can be concluded that the time from the packaging to the consumption of bighead carp's head should not exceed 60 hours during the conventional fresh logistics transportation.(2)Taking freshly slaughtered,slaughtered and left at room temperature for 6 h,simulating fresh-keeping transport for 36 h and 72 h,the bighead carp's head was used as a sample to study the cause of the difference in odor of the carp head samples at different time intervals.The volatile extracts were prepared by simultaneous distillation extraction(SDE)and fractionation,and the volatile flavor compounds in the extract were analyzed by gas chromatography-mass spectrometry(GC-MS).The results showed that there were differences in the composition and content of volatile flavor compounds in different samples.A total of 66 volatile flavor compounds were detected from all samples,and the volatile flavor compounds detected in the 0 h,6 h,36 h and 72 h were 35,31,33 and 38,respectively,including alcohols,aldehydes,esters,aromatics,hydrocarbons and others.(3)Using Metagenomic techniques to analyze the fish brain,and muscles near the eye,chin and incision as evaluated samples through OTU,species diversity curve,alpha diversity analysis,beta diversity analysis and taxonomic composition analysis.The results showed that the OTU value of the muscle near the incision was the highest and the fish brain was the lowest.The number of OTUs in the four parts decreased during the transportation.Species diversity curve analysis showed that with the extension of transportation,the species richness of the same part of the head decreased gradually,and the species uniformity was not high.According to the taxonomic analysis,at the level of the door,the flora is mainly composed of Firmicutes and Proteobacteria;at the genus level,the bighead carp's head is mainly composed of Streptococcus and Lactococcus(4)To explore the changes of fatty acids during fresh logistics transportation of the bighead carp's head by gas chromatography.The results showed that the fatty acids in the four different parts of the head was mostly monounsaturated fatty acid(MUFA)>saturated fatty acid(SFA)>polyunsaturated fatty acid(PUFA),and with the fresh transportation prolonged,the fatty acid content of different types decreased significantly.