The Study On Preparation And Vitro Antioxidant Activity Of Almond Peptides

Almond contains approximately 30% protein and is a potential source of plant protein. The almond protein, in its original form, has some unknown bioactive peptides, which upon enzymatic hydrolysis will liberate a number of them. So, studying almond protein can prepare the bioactive peptides needed by humans which is the effective way to further develop almond protein.In the basic of domestic and foreign studies, in this study, the extraction procedure of almond protein was optimized, and then the double-enzyme hydrolysis assay was applied for almond peptide preparation and the process conditions were researched. The almond peptide was purified and the antioxidant activity of each composition was investigated. And the molecular of peptides which has the strongest oxidation resistance was studied. This can be used to study and develop almonds peptide that has oxidation resistance, and provide a theoretical basis for the application of bioactive peptides of almonds in the food fields. The results were shown as follows:(1) The extraction of almond protein: four single factors of the extraction temperature, pH of protein solution, extraction time and solid-liquid ratio were analyzed. The results showed that almond protein extraction rate can reach 72.16% in the condition of extraction temperature 53℃,pH 9.0, extraction time 65min, solid-liquid ratio1:22(g/ml).(2) Double enzyme hydrolysis of almond peptides preparation and the oxidation resistance: different proteases were used to hydrolyze almonds protein, according to the protein hydrolysis degree (DH). The results showed that neutral protease and pineapple protease enzyme complex (mass ratio 1:1) were selected as the most appropriate enzyme. The orthogonal test was adopted to optimize the preparation of almond polypeptide hydrolysis condition, according to the ·OH scavenging activity. The results showed that the optimum condition for preparing almonds peptides with high ·OH scavenging activity were: pH 7.5, the ratio of enzyme to substrate 3%, enzyme concentration 4.5%, temperature 50℃, enzyme hydrolysis time is 2h. Under this condition, the ·OH scavenging activity of the peptides obtained is 56.58%. In this dissertation, the antioxidant properties of ASPs are evaluated using different antioxidant tests in vitro; and the obtained enzyme hydrolysis’s provided strong antioxidant activity.(3) Separation of Almond peptide and the molecular weight of the peptide were determinated: almond protein hydrolysis was separated by ultra filtration and got the molecular weight of four different kinds of components, the molecular weight components, the molecular weight range:<1KDa,1K-3KDa,3K-5KDa, >5KDa.1K-3KDa which share the quality of the components of the largest share strongest antioxidant, the light absorption value scavenging ·OH radical capacity and scavenging·O2 radical capacity were 0.51、 60.91% and 50.89% respectively. Molecular weight range of the almonds enzyme 1K-3KDa SephadexG-25 gel products were further purified by column chromatogram, the two molecular weights were obtained, as P Ⅰ、PⅡ. The two constituents have strong antioxidant capacity, PⅡ of the light absorption value ,scavenging·OH radical capacity and scavenging·O2 radical capacity were 0.78、70.12%、62.30%, which is much higher than 1K-3KDa .So PⅡ was the main composition of the 1K-3KDa, and its molecular weight is 1395Da.