Browsing by Author "Mohamed, Chahbar"

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    Bacterial Population Kinetics and Physicochemical Profiles in Fermented Goat Milks: Roles of Streptococcus thermophiles ATCC19258 and Lactobacillus bulgaricus ATCC11842
    (National Nutrition and Food Technology Research Institute, 2025) Tayeb, Silarbi; Morsli, Amirouche; Saadia, Laabas; Mohamed, Chahbar; Khaled, Hamden; ben Salah-Abbes, Jalila
    Background and Objective: The fermentation of Algerian goat milk, a process for the production of valuable dairy products, relies on the synergistic activity of Streptococcus (S.) thermophilus and Lactobacillus (L.) bulgaricus. However, a significant knowledge gap is seen regarding the precise dynamics of these starter cultures within the unique matrix of Algerian goat milks. Specifically, the intricate relationships between their growth patterns and the resulting physicochemical changes, which regulate the distinct biochemical characteristics of fermented products, are poorly understood. So, this study addressed this problem by studying specific contributions of S. thermophilus and L. bulgaricus to goat milk fermentation. Material and Methods: Goat milk was fermented by starter cultures of S. thermophilus and L. bulgaricus (8 h). Bacterial growth and physicochemical parameters, including pH, titratable acidity, viscosity and syneresis, were assessed. Mixed-effects models were used for statistical analysis to assess the relationship between physicochemical changes and bacterial growth. Results and Conclusion: The results showed a strong relationship between L. bulgaricus and the control of acidification, viscosity and syneresis (r = 0.979 for titratable acidity, p < 0.0001). S. thermophilus contributed significantly, particularly to the increases in viscosity (r = 0.773, p < 0.01). The two species significantly decreased the pH, with L. bulgaricus having twice the acidifying effects. By the end of the fermentation process, pH reached 4.12 ±0.20, titratable acidity increased to 84.75 ±2.19 °D and viscosity increased to 6425.00 mPa.s ±638.64. The final bacterial counts of S. thermophilus and L. bulgaricus were 519.00 ±115.29×10⁷ and 65.54±6.89×10⁷ CFU.ml-1, respect-ively. In addition to providing a robust statistical framework for process control and quality assurance in fermented milk manufacture, this study highlighted the critical role of L. bulgaricus in regulating structural and sensory qualities of fermented goat milks. Results can be used to optimize fermentation processes for goat milk by strategically manipulating the ratio of L. bulgaricus to S. thermophilus. The strong correlation between L. bulgaricus and acidification, viscosity and syneresis (r = 0.979 for titratable acidity, p<0.0001) provides a clear target for controlling key product attributes