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[3Jp-03] Effects of Lactic Acid Bacteria on the Formation of Casein Network Structure in Yogurt: Comparison of Exopolysaccharides (EPS)
Keywords:yogurt, flavor release, texture, lactic acid bacteria, exopolysaccharide
【Purpose】
Different Lactic Acid Bacteria (LAB) starters produce yogurt with varying levels of sourness despite similar acidity. High-sourness yogurt has larger voids in its casein network, aiding flavor dispersion. The previous studies showed that LAB produces varying EPS amounts and types, affecting yogurt texture, and these structural differences emerge later in fermentation. This study aims to compare EPS production by two starters to reveal differences in casein network formation mechanisms.
【Methods】
Yogurt samples with the same sourness level but different LAB starters—LS (Low-Sourness) and HS (High-Sourness)—were prepared. The casein network structure and EPS were characterized using a Scanning Electron Microscope. EPS was analyzed for molecular weight distribution, charge, and EPS-content produced during fermentation.
【Results】
Microstructural observations indicated differences in casein network formation between LS and HS after reaching pH 5.2. Both samples featured radially distributed short-chain EPS surrounding bacteria, however, LS uniquely exhibited long-chain EPS crossing the casein strands. High molecular weight EPS featured in both starters and LS produced more than HS after pH 5.6. Anion-exchange chromatography showed LS enriched with neutral EPS. The results indicated that the differences in casein network structures correlated with EPS production during fermentation, suggesting that the type and content of EPS influence the formation of the casein network.
Different Lactic Acid Bacteria (LAB) starters produce yogurt with varying levels of sourness despite similar acidity. High-sourness yogurt has larger voids in its casein network, aiding flavor dispersion. The previous studies showed that LAB produces varying EPS amounts and types, affecting yogurt texture, and these structural differences emerge later in fermentation. This study aims to compare EPS production by two starters to reveal differences in casein network formation mechanisms.
【Methods】
Yogurt samples with the same sourness level but different LAB starters—LS (Low-Sourness) and HS (High-Sourness)—were prepared. The casein network structure and EPS were characterized using a Scanning Electron Microscope. EPS was analyzed for molecular weight distribution, charge, and EPS-content produced during fermentation.
【Results】
Microstructural observations indicated differences in casein network formation between LS and HS after reaching pH 5.2. Both samples featured radially distributed short-chain EPS surrounding bacteria, however, LS uniquely exhibited long-chain EPS crossing the casein strands. High molecular weight EPS featured in both starters and LS produced more than HS after pH 5.6. Anion-exchange chromatography showed LS enriched with neutral EPS. The results indicated that the differences in casein network structures correlated with EPS production during fermentation, suggesting that the type and content of EPS influence the formation of the casein network.