From Fermentation to Functionality: Lipidomic Characterization and Index‐Based Evaluation of Plant‐Based Kefir

ABSTRACT This study aimed to characterize the fatty acid composition and to evaluate lipid quality indices of kefir produced with varying ratios of chestnut milk and reconstituted skim milk, using both traditional and commercial starter cultures. Lactobacillaceae counts remained high in all samples (8.35–8.70 log cfu/g on MRS and 8.45–9.35 log cfu/g on M17), while intermediate chestnut milk substitution ratios promoted higher yeast growth than either 100% reconstituted or 100% plant‐based formulations, particularly in samples fermented with grains. Chestnut milk samples fermented with kefir grains or commercial starter cultures exhibited distinct fatty acid profiles and changes in lipid quality during storage. The 20% chestnut milk sample had significantly higher levels of butyric, caproic, caprylic, capric, myristic, and palmitic acids and α‐linolenic acid. In contrast, the 100% chestnut milk sample exhibited the highest concentrations of linoleic and γ‐linolenic acids. Fermentation with kefir grains resulted in elevated butyric, caproic, capric, palmitic, margaric, and arachidic acids, as well as polyunsaturated linoleic acid. Samples fermented with a commercial starter culture contained higher levels of oleic, γ‐linolenic, α‐linolenic, nonadecylic, and gadoleic acids. Throughout storage, short‐ and medium‐chain fatty acids and polyunsaturated fatty acids (ω‐6 and ω‐3) decreased, while palmitic, margaric, oleic, and arachidic acids increased. The 20% chestnut milk sample had the highest contents of saturated fatty acids, total ω‐3 fatty acids, and short‐ and medium‐chain fatty acids. The 100% chestnut milk sample had the highest levels of total unsaturated fatty acids, ω‐6 fatty acids, and long‐chain fatty acids. Lipid quality indices were most favorable in the 100% chestnut milk and commercial starter fermentations, showing lower atherogenic and thrombogenic indices. These results highlight chestnut milk‐based kefir as a low‐fat, functional dairy alternative with an enhanced bioactive fatty acid content and favorable lipid quality indices.