Study On Ultrasound-Assisted Acid And The Mixed Enzyme To Prepare The Anti-Hypertensive Peptide

Laminaria japonica ranks first in the aquiculture area and output,mainly grown in Shandong,Fujian and Liaoning province,and is considered as the vital marine algaes in China for its great contribution to annual economic output of over 4 billion yuan Currently,the intensive processing of kelp focuses on the extraction of sodium alginate,iodine and mannitol rather than the proteins,which causes a great waste in resources.Moreover,the abundant viscous polysaccharide in laminaria japonica tissue makes it hard to undergo proteolysis.Therefore,the research and application of the proteins are restricted.This thesis adopted the ultrasound-assisted acid in the pretreatment,and the mixed enzyme to prepare the anti-hypertensive peptide,and then applied in the production of hypotensive kelp curd.Firstly,combined with the physical effect of ultrasound and the chemical degradation of strong acid,the pretreatment of kelp was carried out by ultrasonic assisted acid hydrolysis.The response surface method was used to calculate the optimal technological parameter:the liquid-solid ratio was 20:1 mL/g,the HCl concentration was 2 mol/L,the ultrasonic power was 300 W,the temperature was 50℃,the experiment was finished in 6 hours.And the result of the experiment showed that the degree of polysaccharide hydrolysis was 45.36%,and the IC50 value of the ACE inhibitory activity was 15.08 mg/mL.All of these datum revealed a decrease in the solution viscosity and inhibitation of polysaccharide after pretreatment.This laid a solid foundation for the pretreatment of the enzyme of the antihypertensive peptides extracted from laminaria japonica.Secondly,the optimal enzymatic conditions were obtained,i.e.,the ratio of alkalic protease to trypsin was 2:1,a pH of 8.5,the dosage of enzyme was 1.5%,the hydrolysis time was 2 hours at pH of 8.5 and temperature of 55℃.Under this condition,the IC50 value of proteinase hydrolysate on ACE activity was 4.14 mg/mL,which was inosculated with the predicted value with relative error of 0.48%.These datum confirmed the practicability of technological parameters obtained from the the response surface method.Lastly,the effects of various factors(e.g.,the dosage of hypotensive fluid in laminaria japonica,the types of coagulant,the concentration of soybean milk and coagulant dosage)on kelp curd quality(e.g.,he flexibility,rigidity,water retention rate,whiteness)were investigated.In addition,the best formula of kelp curd was obtained by sensory score methodology,i.e.,20%(v/v)of hypotensive solution from laminaria japonica,the ratio of composite coagulant to gypsum fibrosum is 2:1,the ration of bean to water is 1:3,the dosage of coagulant is 0.3%.Comparing with the common curd in markets,the kelp curd prevails in every index with high sensory score of 92.5 and an IC50 value of 2.01 mg/mL on ACE activity.The kelp curd not only improves the amino acids balance of beans,but also enhances the flavor and texture of curd,which inspire other scholars to enrich and innovate the exploration of laminaria japonica.