Expeller-Pressed Pomegranate Seed (Punica granatum L.) as a Protein Source for the Production of Antioxidant Peptides

Abstract

Because of health concerns regarding synthetic antioxidants, natural antioxidant compounds are being considered by scientists. Bioactive peptides have been shown to have various physiological functions, such as antioxidative activity. Pomegranate seed protein, the by-product of the pomegranate seed oil industry, can be a good source of bioactive peptides. The optimum conditions for enzymatic hydrolysis of pomegranate seed protein with alcalase were determined using a response surface methodology. The influence of different temperatures (45–55 °C), times (30–180 min), and enzyme to substrate (E/S) ratio (1–3% w/w) on DPPH scavenging power and ferric reducing activity as the responses, were studied. Also, the degree of hydrolysis and the surface hydrophobicity of samples were determined. Moreover, using scanning electron microscopy and electrophoresis technique, microscopic structure and molecular weight of hydrolysate, were studied respectively. Alcalase-derived hydrolysates showed a DPPH scavenging activity (88 ± 0.97%) and ferric reducing power (0.5 ± 0.83) at optimum conditions of hydrolysis (48.8 °C, 97.5 min, E/S ratio 1.3%w/w). The degree of hydrolysis coincided with 36 ± 1.2%. An increase in the surface hydrophobicity of the protein during hydrolysis confirmed the unfolding of the pomegranate seed protein structure. The presence of low-molecular-weight peptides was evidenced by the electrophoresis technique. As well as the SEM showed that protein fragments had been reduced to small sizes following enzymatic treatments. According to the results of this study, pomegranate seed protein hydrolysate can be considered a suitable source of antioxidants with an aggregate market value in food formulations.