Chemical, Microbiological, and Functional Characterization of Kefir Produced from Cow’s Milk and Soy Milk

Table 9

Antibacterial activity of kefir against E. coli, S. Typhimurium, and S. aureus.

Type of kefir	CFS conc.	E. coli (CFU mL^−1)	S. Typhimurium (CFU mL^−1)	S. aureus (CFU mL^−1)
Fermented cow’s milk (cow’s milk kefir)	100% CFS	NG (−)	NG (−)	NG (−)
	75% CFS	NG (−)	NG (−)	NG (−)
	50% CFS	NG (−)	NG (−)	NG (−)
	25% CFS	NG (−)	NG (−)	NG (2.0 × 10^3)
	Unfermented CFS	G (>1.5 × 10^5)	G (>1.5 × 10^5)	G (>1.5 × 10^5)
Fermented soy milk (soy milk kefir)	100% CFS	NG (−)	NG (−)	NG (−)
	75% CFS	NG (−)	NG (−)	NG (4.0 × 10^2)
	50% CFS	NG (−)	NG (−)	NG (6.7 × 10^3)
	25% CFS	NG (−)	NG (−)	G (5.3 × 10^4)
	Unfermented CFS	G (>1.5 × 10^5)	G (>1.5 × 10^5)	G (>1.5 × 10^5)
Nutrient broth		G (>1.5 × 10^5)	G (>1.5 × 10^5)	G (>1.5 × 10^5)

CFSs were inoculated with 3.5 × 10⁵ CFU of E. coli, 3.1 × 10⁵ CFU of S. Typhimurium, and 2.0 × 10⁵ CFU of S. aureus. G/NG: growth or no growth observed by turbidity. Samples were taken, inoculated, and enumerated in nutrient agar. Viable counts in nutrient agar are shown in parentheses. CFS was considered as bactericidal when no viable counts were observed.