Investigating thermal denaturation kinetics of 7S and 11S proteins and lipoxygenase in soymilk through ohmic heating

Abstract

The purpose of this study is to investigate denaturation kinetics of 7S and 11S proteins as well as lipoxygenase in soymilk during ohmic heating treatment. Because denaturation kinetics of 7S and 11S are nth‐order reaction, a reaction order was estimated based on experimental data and simulation results using Arrhenius parameters calculated through differential scanning calorimetry dynamic method. Denaturation kinetic of lipoxygenase was determined by denaturation ratio which estimated based on oxygenase activity of its after ohmic heating treatment at 65, 70, and 72.5°C. The reaction orders of 7S and 11S proteins during ohmic heating of raw soymilk were determined as 3.25 and 1.52, respectively; while the reaction order of 11S protein in preheated soymilk at 75°C for 1 h was found to be 1.94 with a good correlation between experimental data and simulation result. Electrophoresis results indicated that trypsin inhibitor might affect the denaturation of 11S protein during ohmic heating. The denaturation of lipoxygenase during ohmic heating followed a first‐order reaction at all temperatures, and denaturation simulation using the Arrhenius parameters corresponded well with the experimental data.Practical ApplicationsThis study provides valuable insights into improving a quality of soymilk products. 7S and 11S proteins play a critical role in determining viscosity of soymilk and tofu made from soymilk, which together account for a large proportion of the total proteins in soymilk. Understanding the thermal denaturation kinetics of 7S and 11S proteins can help food manufacturers optimize their processing parameters to achieve the desired physical properties of soymilk. Moreover, lipoxygenase is responsible for producing beany flavor components in soymilk, and understanding its thermal denaturation kinetic can lead to production of soymilk with high consumer acceptance. Our research supports a practical application of ohmic heating technology in the processing of soymilk.

Effects of pH and salt concentration on freeze–thaw fractionation of soymilk protein

“…To determine the optimal pH conditions in raw soymilk during freeze–thaw fractionation, densitometry analysis was performed on the result of SDS‐PAGE. This analysis was conducted using ImageJ software (US National Institutes of Health, Bethesda, MD, USA) following our previous reports 24,25 . Briefly, band intensities of 7S (α, α′, and β subunits) and 11S (acidic and basic polypeptides) globulins in grayscale images of the SDS‐PAGE gel were measured using ImageJ software.…”

“…This analysis was conducted using ImageJ software (US National Institutes of Health, Bethesda, MD, USA) following our previous reports. 24,25 Briefly, band intensities of 7S (⊍, ⊍ 0 , and ⊎ subunits) and 11S (acidic and basic polypeptides) globulins in grayscale images of the SDS-PAGE gel were measured using ImageJ software. The 11S/7S ratios were determined by comparing the total band intensities of 11S to those of 7S, aiming to evaluate their relative abundance in the supernatant.…”