Research On The Preparation Of Soybean Antioxidant Peptides By Ultrasonic Technology

This reseach was granted by"the Double Ten Project of ChangChun city?15SS090?.Since Harman put forward the theory of free radicals,people recognized that free radicals in human body were related to many diseases,such as Alzheimer's disease,cardiovascular disease,aging andso on.Therefore,antioxidants were attracting more and more attention.The synthetic antioxidants were widely used in the food industry because of the advantages of low price and high yield.However,with the development of economy,people payed more and more attention to health.People have been more attracted to natural antioxidants which were safe,natural and non-toxic side effects,such as tea polyphenols,ascorbic acid and protein peptides,etc.In recent years,it has been found that soybean antioxidative peptides had strong functions of scavenging free radicals in vivo and inhibiting the peroxidation of biological macromolecules,and soybean antioxidative peptides were characterized by low toxicity and high efficiency.Therefore,this study discussed that SPI treated by ultrasonic technology was prepared soybean protease hydrolysates,the research contents and main results were as follows:?1?The effects of different ultrasonic power and ultrasonic time on the structure of SPI were investigated.The results showed that surface hydrophobicity,fluorescence spectrum,Zeta potential and average particle size of SPI treated by ultrasonic with different conditions were significantly changed?p<0.05?.Protease hydrolysates were prepared by SPI treated with different ultrasonic conditions,and the antioxidant activity of protease hydrolysates was measured.The results showed that the antioxidant activity of soybean protease hydrolysates was improved?p<0.05?in degree,and the ultrasonic power was 400W,the ultrasonic time was15min,the DPPH,ABTS scavenging rate of the soybean hydrolysate reached the maximum value of 59.36%±0.85,65.02%±0.78.Compared with those without ultrasonic enzymatic hydrolysis,the antioxidant activity of the hydrolysates increased by 17.16%and 11.9%.When the fixed ultrasonic power was 400W,the ABTS scavenging rate reached the maximum in 15min,and the DPPH clearance rate reached the maximum at 25min.While the ultrasonic condition 400W,15min and400W and 25min were not significantly different?p>0.05?.The enzyme hydrolysates with the ultrasonic condition of 400W and 15min were further analyzed.?2?Separation of samples from the last step by ultrafiltration,the components of the four soybean antioxidant peptides?SAP?with molecular weight<1 k Da,1k Da³k Da,3 k Da¹0 k Da and?10 kDa were named as SAP-1,SAP-2,SAP-3 and SAP-4.The antioxidant activity of ultrafiltration components were comprehensively evaluated with the DPPH,ABTS inhibition taken as evaluation indexes.The results showed that SAP-1 had the strongest antioxidant activity.The total amino acid content of SAP-1 was 444mg/g,with the highest content of Cys,and the lowest content of Met.SAP-1 was used as the subject,and the male mice were subjected to 8weeks of gastric irrigation experiment,and the levels of MDA,SOD,CAT and GSH-Px in the serum of mice were the evaluation indexes of antioxidant activity in vivo.Compared with the blank group,the experimental groups ware significantly?p<0.05?improved the level of SOD,GSH-Px and CAT in the serum of mice,and significantly?p<0.05?lower the MDA level.There was no significantly?p>0.05?different in body weight,organ coefficient compared with blank group.?3?SAP-1 was purified by gel chromatogram,four elution peaks were obtained and named SAP-1-??SAP-1-??SAP-1-??SAP-1-?respectively.The antioxidant activity of four elution peaks were comprehensively evaluated with the DPPH,ABTS inhibition taken as evaluation indexes.The results showed that SAP-1-?had the strongest antioxidant activity.The amino acid analysis showed that the content of amino acid was 684mg/g,with the highest content of Cys,and the lowest content of Met.The structure of SAP-1-II was identified by mass spectrometry,and 13 amino acid sequences were identified.?4?The optimum parameters of ultrasonic treatment of SAP-1 were optimized through single factor and response surface experiments,as well as the effect of ultrasonic technology on its structure was analyzed by FTIR and Zeta potential.Using a response surface methodology?RSM?experiment,it was shown that when ultrasonic power was 370W,ultrasonic time was 19min,work interval ratio was 3/3,the DPPH,ABTS radical inhibition of SAP-1 increased to 89.62%±0.38,82.85%±0.81,and the antioxidant activity increased by 13.08%,8.13%compared with the non-ultrasonic treatment sample.FTIR analysis indicated that the ultrasonic-treated SAP-1 under optimal conditions added the characteristic absorbance of C=CH₂ and-CH₃;As well as the ultrasonic-treated SAP-1 of Zeta potential was decreased by 8.63mV,It was further speculated that SAP-1 was more disordered by ultrasonic treatment,resulting in the exposure of functional groups and the change of antioxidant activity of SAP-1.The results not only showed the mechanism of ultrasonic technology to improve the activity of antioxidant peptide,but also provided the reference basis for the change of SAP-1 structure.