Antioxidant activity, functional property and flavour of Maize protein hydrolyzed by endo- exo proteasee

Abstract

The objectives of this study were to improve the antioxidant activity, functional property, volatile compounds, and organoleptic quality of maize protein by endo-exo protease. Maize (Suwan 1) was hydrolyzed by various concentrations of Protease PF51® (0, 10, 15% w/w) and hydrolysis time (0.5, 3, 6, 12 h) to produce maize protein hydrolysate (MPH). The degree of hydrolysis (DH), antioxidant activities, foaming capacity, molecular weight distribution, volatile compound and sensory evaluation were investigated. Antioxidant properties of the MPHs resulted in strong scavenging activity against DPPH• and ABTS•+ radicals, and their antioxidant activities were dose-dependent, and positively correlated with the increase of degree of hydrolysis. Conversely, the foaming capacity decreased with the DH increasing. The molecular weight distribution estimated by sodium dodecyl sulfate- polyacrylamide gel electrophoresis (SOS-PAGE) indicated that Protease PF51® could hydrolyze native maize proteins into low molecular weight peptides with their sizes less than 10 kDa. The volatile flavour compounds of MPHs were analysed on a dynamic headspace solid-phase microextraction-gas chromatography-mass spectrometry (DHS-SPME-GC-MS). The predominant volatile flavour compounds were 2-ethyl-1-hexanol, benzaldehyde, benzeneacetaldehyde, methoxy- phenyl-oxime, 2-methoxy-4-vinylphenol, 1-hexadecanol and linoleic acid ethyl ester, which odours are described as being sweet, floral, green and fatty. The volatile profile of the MPHs was consistent with the flavour characteristics that were determined by the sensory evaluation. Quantitative descriptive analysis was applied for sensory evaluation. The panellists described the flavour characteristics of the MPHs as having sweet taste, umami taste and maize odour. Moreover, the MPHs had no bitter taste. The sweet taste, bitter taste and maize odour intensity of the protein hydrolysates depended on the DH. The optimal hydrolysis conditions for the production of MPH were 10% Protease PF51® for 3 h with a degree of hydrolysis of 50.00%, OPPH• scavenging activity of 50.58%, ABTS•+ scavenging activity of 40.77% and foaming capacity of 86.24%.