Effect of walnut oil on the fatty acid content of probiotic kefir produced either with kefir grains or kefir starter cultures

The effect was determined of the addition of walnut oil, fermentation and storage time on the composition, microbiota and fatty acid (FA) content of kefir made with kefir grains and direct vat set starter cultures plus the monocultures of Lactobacillus acidophilus LA-5 and Bifidobacterium animalis subsp. lactis BB-12. The addition of oil did not change the proportions of the microorganism groups; however, the amount of polyunsaturated FAs increased. The fermentation process did not alter the FA content. Nonetheless, during refrigerated storage, its content underwent a change. Decreases were noted in conjugated linoleic acid (CLA), strearic, vaccenic, γ-linolenic, eicosenoic acid content, while increases in selected short- and medium-saturated FAs were observed. The amount of capric, lauric, myristic, palmitic and margarine FA increased during the storage of kefir with oil addition. However, the possibility of producing kefir with kefir grains or industrial probiotic kefirs naturally enriched in CLA has been excluded.