| Our country has vast sea area with rich marine resources. Scallop plays an important position in ourmarine resources.They have certain values in development and application with their delicious, nutritional and healthy. As constantly improving of our farming and fishing technique, the production of scallop has gradually increased year by year.But due to the relative backward processing, products are most focused on the frozen and dried low-valued products and high-valued products is relatively less, scraps from the improper handling are easy to rotten. It has not only leaded to the waste of the scallop resources, but also caused environmental pollution in the zone of the breeding and fishing.The traditional aquatic product processing in China is simple. On account of low utilization of the waste, in this study, the by-products from processing of scallop skirt was as the research object which was hydrolyzed with different kinds of protease. We screened out two kinds of proteases based on sensory index.The hydrolysis condition of these two proteases was optimized with the single-factor experiment and response surface methodology (RSM). With the optimum conditions the two proteases was used to hydrolyzethe scallop skirts egmentally. The amino acid of the hydrolysate was analysed by high performance liquid chromatography method (HPLC). Electronic nose and electronic tongue technique was applied to conduct smell and taste recognition research of different enzymatic hydrolysate from scallop skirt.Over the past decade, researchers from domestic and foreign have made a lot of studies about enzymatic hydrolysis of shellfish to prepare flavor enhancer and conducted extensive research on its effectiveness of the biological activity. Currently, frozen or dried are the main mean of processing shellfish. Scallop skirt possesses unique seafood flavor as the scallop. It is believed that there are so many advantages to prepare flavor enhancer from the low-valued scraps of the seafood with protease. For example, the extraction processing is simple, it’s easy to preserve the product and there will be less environmental pollution. The use of animal or plant protein for making condiment has now become a hot research topic.In this study, scallop skirt was hydrolyzed with neutral protease, papain, alkaline protease, trypsin and flavourzyme to prepare flavor enhancer. The flavor and recovery indexs of hydrolysis were evaluated. According to the result, neutral protease and alkaline protease were suitable for the hydrolysis of scallop skirt. Based on the single factor experiment, the response surface methodology (RSM) was employed to investigate the influence of main factors on the degree of hydrolysis (DH) to establish a regression model. The conditions of hydrolysis for scallop skirt were optimized by RSM. Then scallop skirts were hydrolyzed with neutral protease and alkaline protease and the amino acid content of the hydrolysis was analyzed by High performance liquid chromatography (HPLC). The conditions of hydrolysis for scallop skirt were optimized by RSM as follows:For neutral protease, substrate concentration was7%, concentration of enzyme was23.1thousand (U/g dry matter), hydrolysis temperature was49.1℃, pH was7.8, hydrolysis time4h, the optimized DH could reach50.4±0.05%, The experimental values agree with those predicted from the regression model within a relative error of1.09%. For alkaline protease, substrate concentration was7%, concentration of enzyme was23.3thousand (U/g dry matter), hydrolysis temperature was60.9℃,pH was11.3, hydrolysis time was4h, the optimized DH could reach49.9±0.04%. The experimental values agree with those predicted from the regression model within a relative error of1.09%and5.90%. Both of the two models had good fitness.Furthermore, scallop skirt wassegmented hydrolysedwithalkaline protease and neutral protease, the amino acid components of different enzymatic hydrolysis conditions were determined with high performance liquid chromatography (HPLC). The results showed that the total free amino acid of the hydrolysis with alkaline protease was165mg/g, including essential amino acids50.9mg/g. The total free amino acid of the hydrolysis with neutral protease was133mg/g, including essential amino acids53.1mg/g. There were19kinds of free amino acid in the segmented hydrolysate with total amino acid content230mg/g, essential amino acids72.4mg/gand taurine13.8mg/g. The results showed that there was especially high content of glycine, arginine and glutamic acid and so on.Traditional sensory evaluation was often effected by subjective factors leading to inaccurate results. Electronic nose and electronic tongue technique was applied to conduct smell and taste recognition research of different enzymatic hydrolysate from scallop skirt and analysed the difference between different smell and taste index of the enzymatic hydrolysate. The results of electronic nose showed that the strength order of hydrolyzate made from six kinds of protease was segmented hydrolysis made by alkaline protease and neutral protease>alkaline protease (scallop skirt without boiled)>neutral protease>trypsin>flavourzyme>alkaline protease (scallop skirt with boiled in advance). Hydrolyzate analysis of electronic tongue showed that the umami intensity of segmented hydrolyzate made by neutral protease and alkaline protease was strongest. The order of umami intensity was segmented hydrolysis made by alkaline protease and neutral protease> alkaline protease (scallop skirts without boiled)> alkaline protease (scallop skirt with boiled)> neutral protease> trypsin> flavourzyme. The order of sour intensity was opposite to the umami. There was no significant difference in aftertaste of bitter and astringent of six kinds of enzymatic hydrolyzate. In addition, the test result showed that the hydrolysate of scallop skirt boiled before would lose part of flavor substances, especially umami. It was not good for the preparation of flavor enhancer. The results agreed with the preliminary amino acid analysis test. Six enzymatic hydrolyzate differently treated could be distinguished effectively with electronic nose and electronic tongue. This study has provided a reference for the traditional physical and chemical index with electronic nose and electronic tongue. |
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