Microstructural, Volatile Compounds, Microbiological and Organoleptical Characteristics of Low-Fat Buffalo Milk Yogurt Enriched with Whey Protein Concentrate and Ca-Caseinate during Cold Storage

Yogurt is a popular fermented milk product across the world. Structure, taste, and odor characteristics are created by fermenting yogurt with diverse ingredients and lactic acid bacteria (LAB), which contribute the most to the acceptance and quality of yogurt. In this study, low-fat buffalo milk yogurts (LFBY) were produced with the enrichment of 1% (w/w) whey protein concentrate (WPC) and Ca-caseinate (Ca-CN). Yogurts were analyzed based on microstructural, microbiological, organoleptical properties; volatile compounds (solid-phase microextraction method associated with gas chromatography-mass spectrometry) during cold storage for 21 days. Yogurts enriched with WPC and Ca-CN had higher total solids, total protein contents, and pH values. A total of 36 volatile components were identified in all produced yogurts. Acetic acid, butanoic acid, acetaldehyde, acetoin, 2,3-butanedione, ethanol, and 1-heptanol were found in significant amounts and mainly contributed to organoleptical properties. Interestingly, the focused volatile compounds that improve taste and odor were higher in LFBY+WPC yogurt than in plain LFBY or LFBY+Ca-CN yogurt. The Streptococcus thermophilus and Lactobacillus delbrueckii subsp. bulgaricus viable counts were higher in LFBY+WPC yogurt than plain LFBY or/and LFBY+Ca-CN. Conclusively, yogurt enriched with 1% WPC exhibited the best organoleptical properties and volatile component concentrations. The microstructure of the LFBY with WPC was less compact and dense, and regular, with tiny pores and long and individualized casein filaments than the other treatments. The microstructure of the Ca-CN samples caused a compact structure and coarse than in the control yogurt.