Changes in Fatty Acid Profiles and the Formation of Volatile Organic Compounds During Fermentation of Cow’s Milk with Probiotic Lacticaseibacillus paracasei Strains

In this work, a comparative analysis of the profile of fatty acids (FA) and volatile organic compounds (VOCs) for skimmed cow’s milk fermented by four different probiotic strains of Lacticasibacillu paracasei (ABK, KF1, MA2, and MA3) was carried out. Analysis of FA and VOC profiles was performed using gas chromatography with mass spectrometric detection (GC-MS). For additional characterization of odor changes and its intensity in the fermented milk samples, the E-nose “electronic nose” odor analyzer was used. In total, the presence of 42 different FAs was detected in all samples, of which 17 were saturated, 8 monounsaturated, and 5 polyunsaturated. The strain-specific differences between the studied samples were of a complex nature and could not be explained only by the variation in the contribution of several individual FAs. The FA-nutritional indices characterizing the nutritional and biological value of the samples were different for milk fermented by different strains. Analysis of VOCs showed that the main odor-forming compounds in the studied samples were FAs and their reaction products, 2-heptanone, 2-nonanone, and 2-nonanol, which formed as a result of the following chain of transformations: β-oxidation → decarboxylation → reduction. The aroma of L. paracasei fermentation products, predicted on the basis of the odors of individual VOCs, generally coincided with their organoleptic assessment, a flavor typical of fermented milk (yogurt and curdled milk) with floral and fruity notes.