The changes of Trp-deficient linusorb during the oxidation and the influence of γ-tocopherol on their oxidative stability

Abstract

Linusorbs (LOs), particularly the Methionine (Met)-containing yet Tryptophan (Trp)-free LO (CLB and CLP), play a significant role in shaping the quality and sensory attributes of flaxseed oil. To investigate the stability of these LOs and their oxidized forms during accelerated oxidation, the polar fractions of crude flaxseed oil were selectively removed using silica absorption and then reintroduced separately into the oil matrix along with LOs and γ-tocopherol (γ-T). Through comprehensive analysis of oxidative stability indexes, LOs content changes, oxidation kinetics, and the correlation between LOs and oxidative stability indexes, we observed that the LOs fraction alone exhibited a moderate antioxidant effect on the peroxide value (PV) but a weaker effect on the p-anisidine value (p-AV) of flaxseed oil. However, upon addition of γ-T, we observed a weak synergistic effect between γ-T and LOs in suppressing PV, while a stronger effect in suppressing p-AV. Additionally, a comparison of the oxidation kinetics of different LOs indicated that γ-T preferentially protected the oxidation of CLP over CLB. Similar protective trends of γ-T towards the methionine sulfoxide (MetO) and methionine sulfoxide (MetO₂) form of LOs were also observed, albeit to a lesser extent. Correlation analysis revealed that changes in Met-containing LOs, particularly CLP, showed a high correlation with PV in the tested matrices, while MetO-containing LOs better depicted changes in p-AV. Importantly, CLP demonstrated higher susceptibility to the influence of antioxidants, making it more suitable for evaluating the peroxide value in flaxseed oil samples.