المجلة الجزائرية للعلوم
Volume 8, Numéro 2, Pages 38-47
2025-07-30
Microbiological And Biochemical Characterization Of Pasteurized Cow's Milk
Authors : Haddouche Mohamed .
Abstract
Algeria is considered one of the largest milk consumers in the Maghreb region. Spore-forming bacteria, particularly those of the Bacillus genus, are among the most significant contaminants in milk. The objective of this study was to evaluate the microbiological quality of pasteurized cow's milk. Five samples were collected from a dairy in the Ain Temouchent region and analyzed at an agri-food analysis laboratory in the same area. The results indicated that the total aerobic mesophilic flora ranged from 14 × 10² to 61 × 10² CFU/mL, while heat-resistant flora counts ranged from 110 to 350 CFU/mL. A total of 14 bacterial strains were isolated. Phenotypic identification revealed that 85.71% of the isolates were Gram-positive and 14.29% were Gram-negative. Additionally, 71.42% of the strains were bacilli and 28.58% were cocci. Enzymatic profiling of the bacilli showed that 50% were capable of hydrolyzing starch (amylolytic activity), 70% could hydrolyze casein (proteolytic activity), and 20% exhibited lecithinase activity. Further biochemical testing using the API 20E test kit identified four bacterial species: Geobacillus thermoglucosidasius, Bacillus cereus, Bacillus licheniformis, and Bacillus subtilis. These findings, in line with previous research, confirm that pasteurization does not effectively eliminate heat-resistant endospores, underscoring the need for improved control measures in dairy processing.
Keywords
Pasteurized milk ; Bacteria ; Spores ; Bacillus ; Heat-resistant
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