Preparation of rapeseed peptides by ultrasound assisted enzymatic hydrolysis and analysis of its composition,physical properties and structure
To enhance the added value and application potential of low temperature pressed rapeseed cake,the low temperature pressed rapeseed cake was defatted with petroleum ether,then ultrasound pretreatment was employed to assist in the direct enzymatic hydrolysis using both papain and alkaline protease to prepare rapeseed peptides.Single-factor experiments were conducted to investigate the effects of ultrasound power,ultrasound time,and enzyme addition amount on the yield of rapeseed peptides,followed by optimization of process conditions using response surface methodology.The composition,physical properties and structure of the obtained rapeseed peptides were analyzed.The results indicated that the yield of rapeseed peptides obtained by alkaline protease hydrolysis was higher than that of papain.The optimal process conditions were alkaline protease addition amount 12 289.79 U/g,ultrasound time 21.82 min,and ultrasound power 306.56 W.Under the optimal conditions,the yield of rapeseed peptide was 55.19%,and the molecular weight of rapeseed peptides ranged from 88.02 Da to 1 290.00 Da,with 98.40%of rapeseed peptides less than 500 Da.Compared with the product without ultrasound assisted enzymatic treatment,the content of amino acid of rapeseed peptides increased,the particle size decreased,the absolute value of Zeta potential increased,α-helix and β-folding in the secondary structure increased,β-angle decreased,and the secondary structure was more orderly and stable.In conclusion,ultrasound assisted enzymatic methods does not use solvent,is environmentally friendly and has good product quality,and can be used for the efficient and direct extraction of rapeseed peptides.
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