Microstructural and Rheological Properties of Camel and Bovine Milk Fermented with Five Lactic Acid Bacteria Strains

This study assessed the fermentation performance of five lactic acid bacteria (<i>Streptococcus thermophilus</i>, <i>Lactobacillus delbrueckii</i> ssp. <i>bulgaricus</i>, <i>Lb. helveticus</i>, <i>Lb. casei</i>, and <i>Lactiplantibacillus plantarum</i>) in camel milk (CM) and bovine milk (BM) at 42 °C for 48 h. Fluorescence microscopy revealed lower bacterial viability in fermented CM compared to BM. Acidification kinetics varied significantly between CM and BM, and proteolysis was more pronounced in fermented CM (<i>p</i> < 0.001), with OPA concentrations ~1.3-1.5-fold greater in CM across all strains during fermentation. Scanning electron microscopy revealed more porous, loose protein matrices in fermented CM than in BM, in line with the rheological analyses showing weaker gel networks and lower rheological strength in fermented CM. <i>Lb. casei</i> demonstrated superior adaptability, enhanced viability, balanced acidification, and favorable rheological properties in both milks, highlighting its potential as a possible starter or adjunct culture in fermented dairy products.