Preparation Of Chlorella Antioxidant Peptide And Its Application In Apple Juice

Bioactive peptides are a group of peptides with different amino acid composition and different arrangement of linear or cyclic structure.Antioxidant peptides are a kind of bioactive peptides,which have the functions of inhibiting the peroxidation of biological macromolecules and scavenging free radicals.Chlorella is rich in protein,which is significantly higher than other plant protein sources.Chlorella is one of the important potential protein sources because of its abundant amino acids and balanced composition of essential amino acids.Chlorella peptide is one of the important products of Chlorella protein processing,and it has been proved to have antioxidant activity.However,there is a lack of development of Chlorella peptide related products.In this paper,Chlorella protein was extracted by high-pressure homogenization method;Chlorella protein was hydrolyzed by alkaline protease,neutral protease,papain and flavourzyme,and the yield of each enzymolysis product was calculated.The antioxidant activity of Chlorella enzymolysis product was determined by DPPH method and ABTS method.The better protease and enzymolysis time were selected.Different concentrations of activated carbon were used to decolorize the hydrolysates of Chlorella.The yield,antioxidant activity and color difference of the decolorized products were determined.The better Chlorella polypeptide powder was selected by comprehensive comparison.The molecular weight and amino acid analysis of the polypeptide were carried out to study its properties.Chlorella peptide powder and fresh apple were used as the main raw materials to develop Chlorella peptide functional juice beverage.The best concentration ratio of color fixative was determined by the browning value.Based on sensory evaluation and stability coefficient,single factor test was used to study the amount of juice,peptide powder solution,sugar and different stabilizers;the raw material ratio and stability of fruit juice were studied by orthogonal test and response surface analysis.Finally,the quality index,storage stability and antioxidant activity of fruit juice produced by the optimal process were tested.The results are as follows:(1)Chlorella cell wall was broken by high-pressure homogenization method.Chlorella polypeptide with high yield and strong antioxidant activity was screened by single enzyme hydrolysis method.The specific parameters were as follows: alkaline protease,enzyme base ratio 2%,pH 5,water bath temperature 55 ℃,water bath shaking rate 150 r/min,enzymolysis time: 4 h.The yield of Chlorella peptide was 58.83%,the DPPH half inhibitory concentration was 2.54 mg/mL,and the ABTS clearance capacity was 0.71 m M.(2)The decolorization experiment of Chlorella polypeptide by activated carbon has determined a good preparation process.The specific parameters were as follows: The content of activated carbon was 0.5%(w/v),the temperature of water bath was 25 ℃,and the rate of water bath oscillation was 150 r/min.After decolorization,the yield of Chlorella peptide was69.25%,the DPPH half inhibitory concentration was 2.77 mg/mL,the ABTS scavenging capacity was 0.48 m M,the essential amino acids accounted for 39.63% of the total amino acids,and the hydrophobic amino acids accounted for 35.85% of the total amino acids.The polypeptide with molecular weight of 240.60 Da accounted for 68.66% of the total peptide.(3)Based on the traditional production process,the production process parameters of Chlorella peptide functional juice beverage were determined as follows: color retention time 1h,homogenizer speed 20000 rpm,homogenization time 2 min,sterilization temperature 65 ℃,sterilization time 30 min.Apple slices were treated with color fixative,and the best ratio of color fixative was determined: the concentration of vitamin C was 0.1 g/L,and the concentration of Chlorella peptide powder was 0.4 g/L.Single factor and orthogonal experiments were used to optimize the amount of apple juice,Chlorella peptide powder solution and white granulated sugar.The optimal formula of fruit juice beverage was obtained as follows: apple juice 20 mL,Chlorella peptide powder solution 5 mL and white granulated sugar 5 g.Single factor and response surface analysis were used to determine the optimal amount of CMC-Na,carrageenan and pectin.When the amount of CMC-Na,carrageenan and pectin was 0.14%,0.19% and 0.17% respectively,the stability coefficient was as high as89.72%.The beverage had the best stability.The sensory score of the juice made by the optimal process was 86.6,and the sensory quality was good.The quality index of fruit juice was tested.The results showed that the fruit juice was bright yellow,uniform liquid distribution,no obvious pulp precipitation,sweet and sour taste,mellow taste,strong apple aroma,no algae odor;PH value: 4.08,peptide concentration: 4.76 mg/mL;microbial indicators: total number of colonies ≤ 100 CFU/mL,coliform group ≤ 3 MPN/mL,pathogenic bacteria were not detected.The storage stability of fruit juice was studied.During 90 days storage,low temperature storage was beneficial to the stability of the beverage.DPPH method and ABTS method were used to determine the antioxidant capacity of fruit juice.The results showed that the antioxidant effect of Chlorella peptide functional fruit juice beverage was significantly higher than that of fruit juice without Chlorella peptide powder.