Comparative Evaluation of Yoghurts from Cow Milk and Soybean: Proximate Composition, Physicochemical Properties and Microbial Analysis

Abstract

Aims: To comparatively analyse the proximate composition, physicochemical properties, and microbial quality of yoghurts produced from cow milk and soybeans. Study Design: Laboratory-based comparative analysis. Place and Duration of Study: Department of Biochemistry, Federal University of Technology Owerri, Nigeria. The study was conducted over a period of eight weeks. Methodology: Yoghurts were produced from pasteurised whole cow milk and wet-milled soybean milk, each fortified with skimmed milk powder (2–4% w/v) and fermented with a commercial starter culture containing Lactobacillus bulgaricus and Streptococcus thermophilus. Proximate composition (moisture, ash, protein, fat, fibre, carbohydrate) was determined using standard AOAC (2016) methods. Physicochemical parameters (pH, titratable acidity, viscosity, total solids) were analysed using appropriate instruments, and microbial counts (lactic acid bacteria, yeast/mould, coliforms) were enumerated on selective media. Results: Cow milk yoghurt exhibited significantly higher protein (24.28 ± 0.56%) and moisture (68.79 ± 1.12%) contents. Soybean yoghurt contained higher ash (3.66 ± 0.47%), fat (2.91 ± 0.07%), crude fibre (5.22 ± 0.04%), and carbohydrates (11.81 ± 1.78%). Soybean yoghurt had a lower pH (3.58 ± 0.15) and viscosity (123.10 ± 1.00 mPa·s) but higher total solids (55.84 ± 2.54%). Both yoghurts maintained high viable lactic acid bacteria counts (>10⁷ CFU/g) with no detectable coliforms or yeast/mould. Conclusion: Cow milk yoghurt is superior in protein content and viscosity, while soybean yoghurt offers benefits in fibre, minerals, and total solids. Both products are microbiologically safe and support robust probiotic growth, catering to different dietary needs and preferences.