Study On Preparation And Activity Of Tea-residue Polypeptide

At present,there are more and more studies on the preparation of low-toxicity,high-efficiency natural antioxidant peptides and ACE-inhibitory peptides.However,tea protein is a plant protein with abundant sources and excellent functional components.Most scholars only study to explore the extraction methods and physiological functions,ignore the use of tea proteins to further prepare bioactive peptides with good functions.As a by-product of tea protein,tea residue protein still retains a high protein content,which can be used as a raw material for the preparation of tea slag functional polypeptides,improves new ideas for the multiple reuse of tea residues.This paper attempts to use different proteases and tea dregs protein to prepare tea dregs antioxidant peptides and tea dregs ACE inhibitory peptides;and further use ultrasonic assisted enzymolysis to prepare higher activity tea dregs antioxidant peptides and tea dregs ACE inhibitory peptides;The obtained tea residue antioxidant peptides and tea residue ACE inhibitor peptides were ultrafiltered and roughly separated,and the stability of the separated high-activity components was studied to provide certain background support and theoretical basis for their practical application in the future.The main research contents and conclusions are as follows:?1?Preparation of tea dregs antioxidative peptides and tea dregs ACE inhibitory peptides by different proteasesTea residue protein extracted by inverse microemulsion method was used as raw material,tea residue anti-oxidation peptide was prepared by trypsin,and tea residue ACE inhibitory peptide was prepared by alkaline protease.The reducing power and degree of hydrolysis of the tea residue antioxidant peptides,the ACE inhibitory rate and the degree of hydrolysis of tea slag ACE inhibitory peptides were examined.The reaction surface was used to optimize the enzymolysis process to obtain the reduction of tea residue antioxidant peptides prepared under the following conditions:substrate concentration 2%,enzyme dosage 3034 U/g,pH8,enzymolysis temperature 51°C,hydrolysis time 3 h.The ACE inhibitory rate of tea slag ACE-inhibitory peptides prepared under conditions of force 0.316;substrate concentration2.5%,enzyme dosage 8310 U/g,pH8.5,enzymatic hydrolysis temperature 61°C,and hydrolysis time 2.3 h.54.10%.?2?Study on Preparation of Tea Residue Antioxidant Peptide and Tea Slag ACE Inhibitory Peptide by Ultrasound-assisted HydrolysisUnder the enzymolysis conditions,ultrasonic pretreatment of tea dregs was added to assist tea slag antioxidant peptides and tea residue ACE inhibitory peptides.Ultrasound technology was optimized by response surface:Ultrasonic power 60%,ultrasonic temperature 50°C,ultrasonic time 28 min,and substrate concentration 2.5%,enzyme dosage 3000 U/g,pH8,and enzymatic hydrolysis temperature 51°C,the hydrolysis time time 2.5 h;under this condition,the reducing power of the tea residue anti-oxidant peptide was 0.378;the ultrasonic power was 60%,the ultrasonic temperature 45°C,the ultrasonication time 25 min,and the subsequent hydrolysis conditions were controlled as substrates.The ACE inhibition rate of tea slag ACE peptide was 64.8%at a concentration of 2%,an enzyme amount 8000 U/g,pH of 8.5,an enzymolysis temperature of 60°C,and an enzymolysis time 2 h.?3?Preliminary separation and purification of tea-residue antioxidative peptides and tea slag ACE inhibitory peptidesThe tea residue anti-oxidant peptide and the tea residue ACE inhibitory peptide were separated and purified by ultrafiltration membranes with 10 kD,5 kD and 3 kD molecular weight cut-off.The components with the highest reducing power and ACE inhibition rate after purification were Tpep-4 and Tpep-4',respectively,and their molecular weights were all below 3 kDa.The reducing power of the purified Tpep-4 fraction increased to 0.412 in the pre-purification mother liquor;the ACE inhibition rate of the Tpep-4'fraction increased to 82.3%after purification.The stability of purified Tpep-4 and Tpep-4 components was studied.The results showed that tea dregs had good heat resistance and acid and alkali resistance.The effects of metal ions and food additives on tea dregs antioxidative peptides were studied.The results showed that Zn²⁺and Fe³⁺had a significant effect on the reducing power of tea dregs.The presence of Zn²⁺reduced the reducing power from 0.412 to 0.39.The presence of Fe³⁺increased the reducing power from 0.412 to 0.433.The food additive was resistant to tea dregs.The reducing power of oxidized peptides is weakened,with sodium citrate having the greatest effect.Simulation of tea dregs in vivo digestion?simulated with pepsin+trypsin to simulate the complete gastrointestinal digestion process?,after 8 hours of reaction,reducing power from 0.412 to 0.327,still has good antioxidant activity,indicating tea residue.Antioxidant peptides have a certain resistance to digestive enzymes.The tea slag ACE peptide also has good tolerance to changes in temperature and pH;In addition,different concentrations of salt solution have little effect on its ACE inhibitory capacity,when the salt solution concentration is 1.2mg/mL,the ACE inhibition rate It is69.5%,and its inhibition ability is good.Similarly,the tea slag ACE peptide was digested in vivo.Under the combined action of pepsin and trypsin,the ACE was reduced from 82.3%to 62.2%after 8h,and the ACE inhibitory capacity was still relatively high.ACE inhibitory peptides have stability in the digestive system.