Abstract
Sorghum has a significant amount of proteins, especially kafirin; however, limited information is available on evaluating its potential for peptide antioxidants. The objectives of this study were to: (1) investigate the effects of two key variables, enzyme-to-substrate ratio and reaction time on kafirin hydrolysis using Alcalase; (2) evaluate the antioxidant performances of the hydrolysates and fractions from membrane ultrafiltration and gel filtration; and (3) identify peptide sequences in the antioxidant fraction using MALDI-TOF/TOF MS. Kafirin hydrolysates prepared at enzyme-to-substrate ratio of 0.4 Au/g and 4 h had a good balance of antioxidant activity, yield, and economic efficiency. Medium-sized fraction of hydrolysates (5–10 kDa) from membrane filtration possessed the highest antioxidant activities among various fractions. The fraction also unveiled a good inhibition effect against lipid oxidation in emulsion and ground meat systems. Smaller-sized fraction (F3) collected through gel-filtration chromatography had significantly stronger antioxidant activities than other fractions, and 26 representative peptide sequences were identified in the fraction.
Highlights
Sorghum is one of the oldest known ancient grains and is the third largest cereal crop in the United States
Degree of hydrolysis, total phenolic content, and DPPH radical scavenging activities were evaluated for the resulting hydrolysates with these combined treatments
The scavenging activity was found to be linearly dose-dependent. These results revealed that the free radical scavenging activity is closely related to the Mw distribution of the substrate hydrolysates [37]
Summary
Sorghum is one of the oldest known ancient grains and is the third largest cereal crop in the United States. It is mainly used as animal feed and a starch source for biofuel [1,2]. Driven by the heightened safety concerns over synthetic antioxidants and consumers’ preference for natural ingredients, the development of novel antioxidants has drawn growing interests [3,4]. Peptide antioxidants are naturally existent (e.g., glutathione, carnosine, anserine), and can be produced from dietary proteins, which exert antioxidative performances through multiple pathways such as scavenging free radicals, chelating transition metals, reducing oxidized substances, interrupting the decomposition of hydroperoxide, forming physical barriers to hinder the access of pro-oxidant to targets, etc. Peptide antioxidants are naturally existent (e.g., glutathione, carnosine, anserine), and can be produced from dietary proteins, which exert antioxidative performances through multiple pathways such as scavenging free radicals, chelating transition metals, reducing oxidized substances, interrupting the decomposition of hydroperoxide, forming physical barriers to hinder the access of pro-oxidant to targets, etc. [5,6]
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