EFFECTS OF DIFFERENT STARTER CULTURES ON THE PHYSICOCHEMICAL, MICROBIOLOGICAL AND MINERAL CONTENTS OF YOGHURT
Abstract
Yoghurt is a widely consumed fermented dairy product known for its nutritional, microbial, mineral, and sensory benefits, but its quality characteristics vary with the type of starter culture used. This study evaluated the physicochemical, microbial, mineral, proximate, and sensory properties of yoghurt fermented with commercial starter culture (Sample A), unpasteurized commercial yoghurt (Sample B), whole lime as starter culture (Sample C), and whole lemon as starter culture (Sample D). Standard analytical methods were employed for chemical, microbial, and mineral analyses, while sensory evaluation was conducted using a 9-point hedonic scale. Physicochemical properties varied significantly (p < 0.05): pH 4.11–4.97, total titratable acidity 1.65–1.95%, total soluble solids 23.00–30.00°Brix, and total solids 31.30–37.52%. Microbial analysis showed total plate counts ranging from 2.77 × 10⁷ to 3.60 × 10⁷ cfu/ml, and total bacterial counts of 1.88 × 10⁴ to 3.15 × 10⁴ cfu/ml, with Sample D exhibiting the highest microbial proliferation. Mineral composition differed significantly (p < 0.05): calcium 126.08–186.52 mg/100 ml, iron 0.03–0.04 mg/100 ml, and potassium 168.49–244.77 mg/100 ml, with citrus fruit-based starter cultures (Samples C and D) enhancing mineral content. Proximate composition ranged as follows: moisture 62.48–68.71%, crude protein 5.31–7.48%, crude fat 0.68–1.10%, total ash 1.21–1.36%, and carbohydrate 23.14–28.80%, reflecting variations in fermentation efficiency. Sensory evaluation indicated significant differences (p < 0.05) in appearance, consistency, aroma, taste, and overall acceptability, with Sample A being most preferred. The study concluded that the type of starter culture significantly influenced the physicochemical, microbial, mineral, proximate, and sensory qualities of yoghurt, with citrus fruit-based cultures improving mineral content and commercial starter culture yielding superior sensory acceptability, indicating the potential for developing yoghurt products tailored for nutritional and sensory benefits.
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