Study On The Processing Of Silver Carp Fish Bone Enzymatic Thick Soup And Flavor Enhancing Techniques

Surimi and surimi seafood are the fastest-growing aquatic products, their productions had reached more than962,000tons in2010in China. The surimi seafood processes utilize ratio are only25%to30%and leave more than70%of solid waste called by-product. By-product consists of heads, bones, scales and skin besides fish gills and visceral, which are rich in protein, fat, minerals and other nutrients, and they are currently only used for producing fish powder and fish oil. In this study, the by-products of silver carp were used as raw materials for the preparation of thermal reaction meat flavor compounds, fish bone soup and enzymatic hydrolysis of fish bone condensed soup. The effects of cooking methods and enzymatic hydrolysis conditions on the quality of fish soup were investigated. Moreover, the effects of thermal reaction conditions and ingredients on the flavor compounds were also studied. In addition, the volatile components of fish bone soup, enzymatic hydrolysis of fish bone condensed soup and thermal reaction meat flavor material were analyzed by SPME-GC-MS. The main results are as follows:(1) The effect of cooking conditions on nutrition and flavor of fish soup was studied. The effect of solid-liquid ratio, cooking temperature and time on the nutrition and flavor of the boiled and autoclaved fish soup were investigated. Orthogonal experiments were used to optimize the cooking conditions. The optimum process parameters of boiling at normal pressure was water ratio of1:1.5,100℃,2.5hours; while autoclaving method was water ratio of1:1,120℃,1.5hours. Moreover, the difference between boiled and autoclaved fish bone soup was investigated. The results indicated that the contents of total solids, protein, water-soluble protein, calcium and ash of antoclaved fish bone soup were significantly higher than that of boiled fish bone soup. While the content of monounsaturated fatty acid of antoclaved fish bone soup was14.16%higher than that of boiled fish bone soup. The volatile components were extracted and determined by headspace solid phase micro extraction and gas chromatography-mass spectrometry,63kinds of volatile components were identified from antoclaved fish bone soup, while25kinds detected from boiled fish bone soup.(2) The effect of hydrolysis conditions on flavor of fish bone soup was studied. The effects of various factors on the nitrogen yield and hydrolyzing degree of antoclaved fish bone soup were analyzed including the substrate concentration, enzyme dosage, time and pH. Orthogonal design was used for the optimization of hydrolysis conditions with hydrolyzing degree and nitrogen yield as indicator. The optimum enzymatic hydrolysis conditions were:pH6.0, substrate concentration8%, E/S2000U/g, reacting time4h. Under this condition, the hydrolyzing degree and nitrogen yield were23.07%and78.17%, respectively. The volatile components of the hydrolysates of antoclaved fish bone soup were isolated and identified, and80kinds of volatile components were identified among them mainly containing aromatic alcohols, aldehydes and furans. Compared with the volatile components of antoclaved fish bone soup, the type and content of volatile components had changed obviously after hydrolyzing. Moreover, the antoclaved fish bone soup was with a strong fish smell, but it is more delicious after hydrolyzing. Furthermore, the enzymatic hydrolysis of fish bone soup was used as material to prepare condensed soup via vacuum concentration and adding other ingredients. The product was pale yellow, solidified at room temperature. The contents of solids, protein and salt of condensed soup were42.17%,13.15%and10.02%, respectively.(3) Preparation of thermal reaction meat flavor compounds and flavor component analysis. The hydrolysates of the by-products were produced using composite enzyme solution. Effect of factors (degree of hydrolysis, the kind and contents of reducing sugars and amino acid, pH values, reaction temperature and time) on the quality of thermal reaction product was studied. The surface response methodology showed that the optimum formulation for the thermal reaction were hydrolysates of4hours, adding9%reducing sugars, including glucose and xylose ratio of1:1,1.30%L-cysteine hydrochloride,1.20%thiamine, and2%glutamate; and the optimum conditions were pH6.0, temperature110℃, time40min. The volatile components of the produced hydrolysates and thermal reaction production were analyzed by SPME-GC-MS. Seventy-nine kinds of volatile components in hydrolysate were identified, among them with hydrocarbons is given priority to, followed by aldehydes and esters. However, seventy-six kinds of volatile components were identified from the thermal reaction products, which followed by ketones and alcohols to aldehydes. It can be seen that there is significant difference between the volatile components of thermal reaction meat flavor material and hydrolysates.