The investigation of the effects of different lactobacillus spp. bacteria on the bioactive, textural, sensory properties and volatile organic compounds of yogurt produced from buffalo milk

This study aimed to investigate the effects of adding different proportions of various Lactobacillus spp. to buffalo yogurt production, along with traditional culture as well as commercial starter culture, on the bioactive, textural, and sensory properties of yogurts, as well as the formation of volatile organic compounds. The strains selected for use in buffalo yogurt production were developed in commercial culture and traditional culture in sterilized skimmed buffalo milk, which was then pasteurized as operational culture and added in combinations of 2.5% to pasteurized buffalo milk. The combinations were as follows: KM: Karamaya (traditional culture) (100%), YC: YC-350 (100%), LC: YC-350 (75%) + L. paracasei (25%), LH: YC-350 (75%) + L. helveticus (25%), LP: YC-350 (75%) + L. plantarum (25%). Buffalo yogurt production was conducted in duplicate, and on days 1, 7, 14, and 21 of storage, physicochemical, microbiological, textural, sensory, volatile compounds, peptide profile, γ-aminobutyric acid (GABA), and free amino acid levels were determined. It has been determined that the use of different cultures and storage time did not have a significant effect on the values of dry matter, fat, ash, and protein (P>0.05); however, it affected pH, titratable acidity, antioxidant activity, syneresis, viscosity, and degree of hydrolysis values (P<0.05). Different culture usage and storage time were found to have a significant effect (P<0.05) on the textural parameters of firmness, work of shear, work of adhesion, but the effect on stickiness value was not significant (P>0.05). It has been determined that different culture usage and storage time have a significant effect on microbiological criteria. It has been determined that adequate viability was ensured in all samples, and they complied with the regulations for fermented products. When peptide profiles were examined, differences between samples were observed from the first day of storage, with differences becoming more pronounced as the storage period progressed. These differences were further highlighted through PLS-DA analysis. All essential amino acids were detected in the V samples, and it was determined that different culture usage influenced the levels of certain amino acids. Significant differences were identified among the samples in terms of GABA concentration, and an increase in GABA concentration was observed as a result of proteolytic activity. Solid phase microextraction (SPME) technique coupled with GC-MS was used to determine volatile components, resulting in the identification of a total of 65 volatile compounds, including acids (4), alcohols (9), aldehydes (8), esters (8), hydrocarbons (6), ketones (16), terpenes (8), and other compounds (6). According to the heat map and PCA analysis results, significant differences were observed between samples containing probiotic cultures (LC, LH, and LP) and those without probiotic cultures (KM and YC). From the perspective of sensory analysis results, while the use of different cultures did not significantly affect color and appearance or structure and texture scores, significant differences were noted in terms of flavor and overall acceptability, with samples containing probiotics (especially those containing L. plantarum) receiving lower preference scores. In conclusion, although the addition of these probiotic strains may slightly decrease sensory preference, it is believed that their inclusion in buffalo yogurt production could be beneficial for health due to the beneficial components they introduce. Keywords: Bioactive, γ-aminobutyric Acid, Lactobacillus spp., Buffalo Yogurt, Free Amino Acids, Volatile Organic Compounds