Abstract
The antioxidant activity of flaxseed protein hydrolysates obtained using five different enzymes was evaluated. Proteins were isolated from flaxseed cake and were separately treated with papain, trypsin, pancreatin, Alcalase and Flavourzyme. The degree of hydrolysis (DH) was determined as the percentage of cleaved peptide bonds using a spectrophotometric method with o-phthaldialdehyde. The distribution of the molecular weights (MW) of the hydrolysis products was profiled using Tricine-sodium dodecyl sulfate-polyacrylamide gel electrophoresis (Tricine-SDS-PAGE) and size exclusion-high performance liquid chromatography (SE-HPLC) separations. The antioxidant activities of the protein isolate and hydrolysates were probed for their radical scavenging activity using 2,2′-azino-bis-(3-ethylbenzothiazoline-6-sulfonate) radical cation (ABTS•+) and photochemiluminescence (PCL-ACL) assays, and for their ferric reducing antioxidant power (FRAP) and ability to bind Fe2+. The hydrolysates were more effective as antioxidants than the protein isolate in all systems. The PCL-ACL values of the hydrolysates ranged from 7.2 to 35.7 μmol Trolox/g. Both the FRAP and ABTS•+ scavenging activity differed among the hydrolysates to a lower extent, with the ranges of 0.20–0.24 mmol Fe2+/g and 0.17–0.22 mmol Trolox/g, respectively. The highest chelating activity (71.5%) was noted for the pancreatin hydrolysate. In general, the hydrolysates obtained using Alcalase and pancreatin had the highest antioxidant activity, even though their DH (15.4% and 29.3%, respectively) and the MW profiles of the peptides varied substantially. The O2•− scavenging activity and the ability to chelate Fe2+ of the Flavourzyme hydrolysate were lower than those of the Alcalase and pancreatin hydrolysates. Papain was the least effective in releasing the peptides with antioxidant activity. The study showed that the type of enzyme used for flaxseed protein hydrolysis determines the antioxidant activity of the hydrolysates.
Highlights
The oxidation of lipids and other labile components of food products results in a reduction in their nutritional value and sensorial quality, as well as a shorter shelf life [1]
The antioxidant activities of the protein isolate and hydrolysates were probed for their radical scavenging activity using 2,21-azino-bis-(3-ethylbenzothiazoline-6-sulfonate) radical cation (ABTS‚+) and photochemiluminescence (PCL-ACL) assays, and for their ferric reducing antioxidant power (FRAP) and ability to bind Fe2+
Among the hydrolysates examined, those obtained using Alcalase and pancreatin were superior in terms of their antioxidant activity
Summary
The oxidation of lipids and other labile components of food products results in a reduction in their nutritional value and sensorial quality, as well as a shorter shelf life [1]. To prevent undesirable changes, antioxidants are applied as additives to limit oxidation Artificial antioxidants, such as butylated hydroxytoluene (BHT), butylated hydroxyanisole (BHA) and n-propyl gallate, are highly effective; their application in foodstuffs is strictly regulated and even forbidden in certain countries because of their potential harmful effects on human health [2]. Oxidative stress, which is an imbalance between oxidative species and endogenous antioxidant systems in the human organism, has been associated with a number of chronic diseases. It can be reduced by exogenous antioxidants found in foods [3]. Pihlanto [2] suggested that protein hydrolysates might be used as natural antioxidants in developing functional foods with increased antioxidant activity
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