Effect Of Low Temperature Plasma On Trypsin And Quality Of Penaeus Vannamei

During postmortem of Penaeus vannamei autolysis of muscle will occur due to the action of endogenous proteases,resulting in softening of the shrimp body,and declining of the shrimp quality.Many studies have found that trypsin in the endogenous protease of Penaeus vannamei has a strong degrading effect on muscles.Trypsin is probably the main enzyme that causes muscle softening after shrimp death.Low temperature plasma has been widely used in the food field as a new non-thermal processing technology.In this paper,low temperature plasma treatment of Penaeus vannamei was carried out,and the effects of low temperature plasma on trypsin activity and structure of shrimp were studied.The effect of low temperature plasma technique on muscle protein and the quality of shrimp during storage were also studied.To provide a theoretical basis for extending the shelf life of Penaeus vannamei.The main research and conclusions are as follows:The hepatopancreas from the head of Penaeus vannamei was extracted and purified by acetone degreasing,30-80%saturation ammonium sulfate precipitation,Q-Sepharose Fast Flow anion exchange chromatography and Sephadex G-50 gel column filtration chromatography.Finally,the molecular weight of trypsin was about 29 kDa,and the specific activity was 523.06 U/mg,the yield was 6.07%.The purification multiple was 10.85.(2)The shrimp trypsin was treated by low temperature plasma with different treatment time and voltage.It was found that with the increase of treatment time and voltage,the activity of shrimp trypsin decreased from 106.42±3.59 U/mL to 49.60±2.71 U/mL,and the surface hydrophobicity and temperature increased significantly(P<0.05),while the pH value and total sulfhydryl content of shrimp trypsin did not show significant difference.SDS-PAGE results revealed that low temperature plasma treatment influenced the changes in the intensity of trypsin bands of shrimp with molecular weight of 29 KDa.Conclusively,the results from the present study indicated that low temperature plasma have ability to inactivate trypsin isolated from the shrimp,due to the conformational change in protein structure.(3)Compared with untreated shrimp,the low temperature plasma treated shrimp had a content of myofibrillar protein,,total sulfhydryl group and ultra-micro Ca2+-ATPase activity decreased significantly(P<0.05),and the surface hydrophobicity increased from 2.27±0.13?g to 5.66±0.02 ?g with the change of treatment time and voltage(P<0.05).The electrophoretic profile of SDS-PAGE exhibited the decrease in intensity of paramyosin bands of myofibrillar protein of Penaeus vannamei,however the intensity of myosin heavy chain and protomyosin bands were elevated,while the new actin bands were observed with the application of low temperature plasma.In general,low temperature plasma technology imparts the changes in the biochemical index of myofibrillary protein of Penaeus vannamei,due to protein cross-linking and aggregation.(4)The effects of low temperature plasma on the quality of Penaeus vannamei during storage at 4? was studied.The results showed that with the prolongation of storage days,the sensory evaluation value,texture characteristics and color difference of Penaeus vannamei treated with low temperature plasma were significantly higher than those of untreated group(P<0.05),which played a significant role in slowing down the increase of pH value and microbial proliferation(P<0.05),but significantly accelerated the increase of TBA value(P<0.05).Therefore,low temperature plasma technology can maintain the sensory,color difference,texture and other quality changes of Penaeus vannamei,which has a significant impact on the pH and microbial indicators that cause the quality changes,and can accelerate lipid oxidation.