Kimchi Fermentation-Driven Detoxification of Flaxseed: Impact on Physicochemical Quality and Antioxidant Potential

Flaxseed (<i>Linum usitatissimum</i> L.) is a rich source of <i>α</i>-linolenic acid (ALA) and lignans but contains toxic cyanogenic glycosides (CGs) that limit its application in foods. This study investigated the efficacy of a specialized <i>Lactobacillaceae</i> consortium in detoxifying flaxseed and the subsequent effects of adding this cyanogenic glycoside-depleted flaxseed (CGDF) to a kimchi matrix. Ground flaxseed and CGDF were added to the kimchi seasoning mixture at concentrations of 0.5%, 1.0%, and 2.0% (<i>w</i>/<i>w</i>) and fermented at 4 °C for 8 weeks. Analytical results confirmed that the fermentation process reduced linustatin and neolinustatin to undetectable levels (<500 mg/kg) and reduced total hydrogen cyanide (HCN) to below the Japanese regulatory limit of 10 mg/kg established under the Food Sanitation Act. During fermentation, CGDF-supplemented groups exhibited a delayed decrease in pH and higher retention of free sugars and vitamin C compared to the control and raw flaxseed groups. Notably, the 2.0% CGDF group maintained high oxidative stability of ALA, which we attribute to a putative antioxidant protection mechanism driven by the bioconversion of lignan glycosides into bioactive aglycones. These findings suggest that incorporating biologically detoxified flaxseed into kimchi creates a functional food system that ensures safety while enhancing nutritional stability. Overall, this work provides foundational evidence for developing safe, nutritionally enhanced functional foods within the One Health framework, integrating food safety, microbial ecology, and improved bioactive compound availability.