Increase in conjugated linoleic acid content and improvement in microbial and physicochemical properties of a novel kefir stored at refrigerated temperature using complementary probiotics and prebiotic

Abstract

Probiotics are living cells and usually modify food contents for health benefit of humans (Roobab et al., 2020). Kefir is a complex-probiotic produced from corresponding grains (Demirci et al., 2019; Kivanc & Yapici, 2019; Tomar et al., 2020) that encompass a consortium of microorganisms (Lim et al., 2019; Mitra & Ghosh, 2020), such as lactic acid bacteria (LAB) containing Lactococcus, Lactobacillus, occasionally acetic-acid producing bacteria, and non-lactose fermenting yeast, with a long-endured association with a natural substance matrix of proteins and kefiran as polysaccharide (Bengoa et al., 2019b; Rosa et al., 2017; Tomar et al., 2020). Lactobacillus acidophilus, L. paracasei, and Bifidobacterium animalis subsp. lactis are due special attention because of their healthand immunitystimulating properties (Bengoa et al., 2019a). L. acidophilus is one of the homofermentative bacteria which directly produce two lactic acid (LA) molecules from one molecule of glucose (Fazio et al., 2020), but heterofermentative ones, including B. lactis, convert glucose to lactic acid and acetic acid (AA) or other volatile compounds (Zareba et al., 2012). In consumption of foods with these probiotics, the GITs of consumers are protected against inappropriate situations including extreme pH alterations, GIT enzymes and excretions, and bacterial accumulation (Živković et al., 2016).