| Freshwater fish is famous for rich nutritional value and is very popular in people's life. It's the important source of high protein, contains 8 kinds of essential amino acids for human body, and rich in unsaturated fatty acids especially DHA and EPA.With the improvement of living standards, plus the change of consumption idea, the demand for freshwater fishes is increasing constantly. Food's nutrition and health, convenience is a new trend in the development of food industry for more and more consumers put nutrition, health in the first place. Establishing the comprehensive evaluation system of freshwater nutritional value will guide people's rational diet and nutrition and health, provide more reasonable guidance for food product development and provide theoretical basis for processing.In this paper, Based on the basis of freshwater fish in Hubei Province, the basic nutrition indexes were measured, nutrient database of freshwater fish was established, the difference of nutritional value among freshwater fish were compared, the relationship between nutritional index and weight was analysed. The amino acid score(AAS), multivariate analysis based on amino acids and fatty acids were used to evaluate the nutrition value of freshwater fish, two comprehensive evaluation models were introduced in this paper,the fuzzy comprehensive evaluation model and the gray system comprehensive evaluation model. The correlation between structure indexes and nutrition indexes was analysed so as to explore several methods to simplify the evaluation process in the future.(1) Nutrition indexes include moisture, crude protein, crude fat, crude ash, fatty acid; amino acids of freshwater fish in four seasons were determined.The results showed that there is variation in nutrients in different freshwater fish species and seasons. The crude protein content in spring and winter is higher than in summer and autumn. But the crude fat content is the opposite of crude protein content while the content in summer and autumn higher than in spring and winter. The proportion of total Amino acid content (of dry kind) is ranged from 50%～80%,17 kinds of amino acid were detected, among them,glutamic acid (Glu), lysine, Ileleucine content is higher. The changes of EAA amount are similar with the total amino acid amount; Semi-EAA amount varies little with season.26 kinds of fatty acids were detected, fatty acid composition varies with different fishes. C16:0, C18:1n9t, C20:1 is with the higher content and ratio, the unsaturated fatty acid content is higher than saturated fatty acid.Basic nutrition indexes of Carassius auratus Linn, Ctenop gharryngodon idellus Cuv.et al, Cyprinus carpio Linn was measured under different weight, the moisture content decreases slightly with body weight, crude fat content vary significantly with weight, and the variation of crude protein content is opposite to crude fat content. Ash content varies little with weight. The total amino acids content varies with weight, the varies of each amino acid is similar with TAA.Fatty acids content increase with weight, but the total EPA and DHA content decrease with weight.(2) According to the ratios and patterns of amino acids recommended by FAO/WHO, the nutritive values of the proteins in freshwater fish were evaluated. The results showed that the amino acid scores (AAS) of 7 kinds of EAA were close to or greater than 1, The AAS of Ileleucine and lysine, phenylalanine + tyrosine are significantly higher than the FAO standards. CS value is less than AAS value, but the CS value of Ile and Lys were close to 1.(3) By applying SPSS, multivariate analysis of amino acids and fatty acids of freshwater fish was given in this paper. Factor analysis was performed for 17 kinds of amino acids of 5 kinds of freshwater fish in four seasons.3 factors were selected whose cumulative contribution of variance accounted to 86.03%.Clustering analysis was adopted to analyze 17 kinds of amino acids of 5 kinds of freshwater fish in four seasons. The 20 kinds of fish were divided into 3 categories while 4 categories were divided Clustering analysis with 3 principal component factors. It seems that the difference between fish groups increased after Factor analysis, but the distance is the same between fish with short distance before Factor analysis.Factor analysis was performed for 26 kinds of fatty acids of 4 kinds of freshwater fish in four seasons.6 factors were selected whose cumulative contribution of variance accounted to 87.46%.Clustering analysis was adopted to analyze these data. Results show that The 16 kinds of fish were divided into 3 categories while 6 categories were divided Clustering analysis with 6 principal component factors. It seems that fatty acids varies significantly with classes and seasons.Clustering analysis was performed for both amino acids and fatty acids, the result was more similar to that of the fatty fish quality. So the comprehensive quality of freshwater fish was greatly affected by fatty acids.(4) Fuzzy comprehensive evaluation model and Gray system comprehensive evaluation model was used in the comprehensive evaluation of freshwater fish. According to fuzzy comprehensive evaluation results, comprehensive nutrition value is the highest in Hypophthalmichthys molitrix Cuv.et al in spring. Grey clustering results showed that most of the freshwater fish were with high nutritional value.(5) TheTPA properties of freshwater fish showed significant differences with seasons and individual. With the weight gain, muscle hardness and springiness increase. TheTPA properties in spring were superior to summer and winter.There were some correlations between the TPA properties and nutrition and physiological indexes which could be seeing in hardeness, adhesiveness, gumminess. |
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