Abstract
The best enzyme to prepare peanut peptides, papain, coupled with microwave irradiation was selected from five common proteases according to the results of the yield of peanut peptides [nitrogen solution index (NSI) in trichloroacetic acid (TCA), TCA-NSI] and the degree of hydrolysis (DH). The main factors that influenced the microwave-coupled enzymatic digestion method were optimized by response surface analysis. The optimal conditions obtained were as follows: microwave extraction time, 9.5 min; power, 600 W; substrate concentration, 4%; enzymatic reaction temperature, 50 °C; enzyme quantity, 6,500 U/g; pH, 7.1 (phosphate buffer, 0.05 mol/L). Under these conditions, TCA-NSI was 62.00% and DH was 25.89%, which is higher than that obtained with either protease hydrolysis or microwave hydrolysis alone.
Highlights
Peanuts are the World's fourth most important source of edible vegetable oil and the third most important source of vegetable protein feed meal [1]
The main chelating mechanism is that the α-amino group, carboxyl group and metal ion can give rise to a five ring; α-amino group, imidazolyl and metal ion can form a six ring; and carboxyl group, imidazolyl and metal ion can produce a seven ring [6]
Many studies have shown that the physicochemical and antioxidant properties of peanut protein hydrolysate were positively related with the degree of hydrolysis
Summary
Peanuts are the World's fourth most important source of edible vegetable oil and the third most important source of vegetable protein feed meal [1]. The dipeptide with Met and His being in C-terminal has higher antioxidant activity, while Trp being in N-terminal has higher antioxidant activity [5] Peptides containing His have antioxidant effects through chelation of transition metal ions. Peanut peptides will have important potential applications due to their physiological function, such as antioxidant activities, scavenging of free radicals, angiotensin-converting enzyme (ACE) inhibitory activity. Peptides can be obtained from either chemical or enzymatic hydrolysis of proteins, but enzymatic hydrolysis is generally preferred from the food safety point of view [8] This preference can be attributed to the fact that chemical hydrolysis can destroy L-amino acids, produce D-amino acids, and form toxic substances such as lysinoalanine and because enzymatic hydrolysis is moderately cheaper, more specific, and less destructive than chemical hydrolysis, which destroys all peptide bonds [9,10,11,12,13]. Degree of hydrolysis (DH) was taken as response variable, and the four factors (including microwave time, microwave temperature, pH, and enzyme concentration) were selected to conduct a response surface analysis (RSA)
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