Analyses On Nutritional Characteristics Of Two Fishes And Changes In Quality Of Frozen Bass

With the development of fisheries and aquaculture and the improvement of people's living standards,the cultured fish with higher nutritional value are gradually favored by consumers.Fish is rich in nutrients,especially EPA and DHA in fish oil have the beneficial effects in preventing cardiovascular disease and promoting the development of fetal brain.At present,researches on the quality of fish meat are mainly focused on the changes in indicators of quality during storage and transportation,there is little information available about the systematic evaluation on the nutritional value of fish in different culture seasons,different species,and different parts.The difference in the nutritional components among different species of fish is a subject worth discussing.In this study,the samples of cultured sturgeons and basses were collected in different seasons to determine their contents of nutritional components,including basic nutritional components such as water,ash,fat and protein,and amino aicds,fatty acids,and 7 kinds of common mineral elements.Differences in nutritional conponents of fish in different seasons,different species and different parts were analyzed.Principal component analysis and cluster analysis were used for their evaluation.Changes in quality of bass meat under ice storage were also investigated.Results were as follows:(1)The nutritional components of sturgeons collected in different seasons were significantly different.Sturgeons collected in spring contained lower fat and fatty acid with higher protein,amino acid and several kinds of mineral element,while sturgeons collected in summer had the highest fatty acid content in four seasons.There were also significant differences in the nutritional components in different parts of the sturgeons: the sturgeons had higher fat content in the abdomen,higher contents of protein and amino acids in the back,and the fat content of the tail was generally higher than that of the back and abdomen.The fat and fatty acid contents of Russian sturgeon were significantly higher than those of other two sturgeons,and it amino acid score was also higher than that of the others.Russian sturgeon and the Siberian sturgeon are found to be more abundant in seven kinds of minerals than the hybrid sturgeon.There were some differences in the nutritional components of basses in different seasons,different species and different parts.The contents of amino acids,fatty acids and various minerals of sea bass in autumn are higher than those in spring.The nutritional characteristics of different parts of the basses were also different: the contents of abdominal fatty acids were higher.Compared with sea bass,largemouth bass has higher protein and ash content,lower fatty acid content,but lower amino acid content in the back,while the mineral contents were basically the same.(2)The results of principal component analysis showed that two principal components were extracted from fatty acid and amino acid of sturgeons respectively,three principal components were extracted from fatty acid and two components were extracted from amino acid of basses,the cumulative contribution rates of variance reached more than 90%.By plotting the principal component analysis scores of fatty acid and amino acid,combined with the clustering analysis results,18 samples of three parts of sturgeons collected in four seasons,including hybrid sturgeon,as well as Russian sturgeon and Siberian sturgeon,were divided into three categories: high amino acid and low fatty acid type;high fatty acid type and low amino acid type.Among 9 samples collected in two seasons(autumn,spring),and taken from three parts of sea bass and largemouth,the four sample including a sample taken from the the abdomen of sea bass collected in autumn(SB-aut-A),a sample taken from the back of sea bass collected in autumn(SB-aut-B),a sample taken from the tail of largemouth bass collected in autumn(LB-aut-T)and a sample taken from the abdomen of sea bass collected in spring(SB-spr-A)had higher nutritional quality.(3)Results of quality evaluation of frozen bass revealed that the pH value,TBA,TVB-N,K value and aerobic plate count increased gradually,the hardness and color decreased gradually during storage period.All indicators exceeded the limit 12 days later and the sensory scores are also lower than acceptable limits,the sensory became unacceptable.Therefore,12 d can be determined as the end point of shelf life of frozen bass.