The Research Of Grass Carp Meat Protein On The Nutrition And Structure Properties In A Microwave Field

Grass carp is one of the main freshwater fish species in China, its market value has great limitations due to living fish is not resistant to storage, with the addition of the current domestic freshwater fish food processing technology, the grass carp itself as a kind of high protein, low adipose food fish resources, its utilization value has not been fully made use of. Microwave technology has been increasingly widely used in every field, microwave food production to speed up the application of microwave technology in fish products research. In some key problems in the process of its application, however, did not get very good solve, such as the changes of the fish protein nutrition and safety in a microwave field, so we need more research o the application of microwave technology in fish processing. This article based on the grass carp fish protein as raw material, by using microwave processing on raw material, and study the changes of basic composition in fish protein after the microwave pretreatment. We also research on the antioxidant activities of fish protein gastrointestinal digests, and the poison of the fish protein rationality and nutrition security under microwave fields. And through the SDS-PAGE, the intrinsic fluorescence spectra, surface hydrophobicity, UV scanning spectrum, circular dichroism spectrum, environmental scanning electron microscopy(ESEM) and other technical research of microwave pretreatment on the change of sarcoplasmic protein structure. The main research contents and conclusions are as follows.(1) For the basis composition of grass carp, the water content of up to 82.36%, followed by protein 13.18%, fat and ash content are less. With the increase of microwave power, the water loss rate in fish gradually accelerated, when reach a certain degree it is not reduced any more, and the quality of fish protein stay invariability. After the microwave pretreatment, the color of fish protein changed significantly, the color index E value presents a downward trend with the increase of microwave power and time, however chromaticity index C value presents a rise trend with the increase of the microwave power and time. The proportion of essential amino acids in fish protein reduced, and more obvious with a higher microwave power.(2) The degree of hydrolysis changes significantly, high microwave power and long microwave time caused the protein degeneration, enzyme loci was hidden, not easy to be digested, hence result in the decrease of digestibility. At a same microwave power, the digestion rate dropped from(21.77± 0.60) % to(9.89 ± 0.21) %, reduced by 54.57% with the prolong of microwave time. One the other hand, when microwave time keep the same,,the digestion rate dropped from(22.32± 0.50) % to(9.89 ± 0.21) %, reduced by 55.69% with the prolong of microwave power. This suggests that the high power microwave for a long time will reduce the fish protein nutritional value.(3) DPPH radical scavenging activity in the gastrointestinal digests of fish protein presents a overall rising trend, with the extension of processing time, and it has a 2.35 times increased compared with 0W 0min untreated sample. 2,2’-azino-bis(3-ethylbenzothiazoline-6-sulfonic acid) diammonium salt(ABTS) radical scavenging activity presents a overall reducing trend, with the extension of processing power and time, it has a 44.77% decreased compared with 0W 0min untreated sample. The reducing power(6.23 times increased) compared to the blank, increased from(0.13±0.01) to(0.94±0.040). An increase of short chain peptides with molecular weight lower than 1000 Da were observed in the gastrointestinal digests.(4) Compared with the liquid chromatographic peak time of contrast from standard substance of acrylamide and hydroxymethylfurfural(HMF), fish protein does not contain harmful products after the microwave pretreatment, and it also has no obvious bacteriostatic activity. Comprehensive changes of mice body weight, blood sugar, the surface morphology and cell morphology of kidney and liver, it shows that there is no obvious toxic reason by microwave processing fish protein in mice.(5) The changes in molecular weight of the fish sarcoplasmic protein are not obvious after the microwave pretreatment. With the increase of microwave power and time, the surface hydrophobicity of sarcoplasmic protein increased, there is no significant difference between ultraviolet absorption peak, secondary structure changes by the spiral and random coil to fold. ESEM observation shows that microwave pretreatment on sarcoplasmic protein has a certain changes for its shape.