Influence of storage time of fermented soghurt on the changes in fat and protein biomolecules through Confocal Laser Scanning Microscopy (CLSM) under refrigeration condition

Abstract

Abstract The aim of the study is to assess the significance of storage duration on fermented Soghurt (soy curd), focusing on changes in fat and protein biomolecules analyzing with CLSM, viscosity measurements, and particle size distributions under refrigerated conditions. Soghurt prepared with 1% yogurt culture (Lactobacillus delbrueckii ssp. bulgaricus and Streptococcus thermophilus) was analyzed for storage stability under refrigerated conditions for up to 15 days measuring the pH, acidity, microbial counts, viscosity, particle size distribution and scanning electron microscopy for structural analysis. Even though lactic counts were not affected significantly during the storage periods, yeast & mold counts and coliform counts were absent up to 15 days during the storage. However, the product could be stored upto 7 days under refrigeration condition (6–8 °C). During the storage period, it was observed that the viscosity of soghurt increased with increase in storage time. Particle size distribution was estimated during the entire storage periods for soghurt and it was observed that smaller particle was mostly found in the range of 3.0–50.0 µm while bigger particles were in the range of 57.0–910.0 µm. Further, larger aggregates with big particle sizes were observed during prolonged storage period. The CLSM study showed the appearance of proteins and fats being dispersed slowly during the storage due to the proteolytic and lipolytic activities of yoghurt cultures after 5 days of storage under refrigeration condition.

Keywords

• Soy yoghurt
• Viscosity
• Particle size distribution
• CLSM
• Lactic acid bacteria
• Storage study