Table 1. Antimicrobial spectrum of four types of kefir fermented for 24, 36, 48, or 72 h against eight food pathogens and spoilage bacteria.
| Kefir | Fermentation time (h) | pH | Inhibition profile1),2) |
|||||||
|---|---|---|---|---|---|---|---|---|---|---|
| BC | SA | LM | EF | EC | SE | PA | CS | |||
| A | 24 | 4.05 | + | − | − | − | − | − | + | − |
| 36 | 3.86 | ++ | − | − | − | − | − | + | − | |
| 48 | 3.81 | ++ | − | − | − | + | − | ++ | − | |
| 72 | 3.70 | ++ | − | − | − | + | + | ++ | + | |
| L | 24 | 3.99 | ++ | − | − | − | − | − | + | − |
| 36 | 3.77 | ++ | − | − | − | − | − | + | ++ | |
| 48 | 3.71 | ++ | + | − | − | − | − | ++ | + | |
| 72 | 3.64 | ++ | − | − | − | + | ++ | ++ | ++ | |
| M | 24 | 3.97 | ++ | − | + | − | − | − | + | − |
| 36 | 3.81 | ++ | − | ++ | − | − | − | + | − | |
| 48 | 3.77 | ++ | + | ++ | − | + | − | ++ | + | |
| 72 | 3.74 | ++ | − | ++ | − | + | + | ++ | ++ | |
| S | 24 | 3.94 | ++ | − | − | − | − | − | + | − |
| 36 | 3.77 | ++ | − | − | − | + | + | + | − | |
| 48 | 3.75 | ++ | + | − | − | + | − | ++ | − | |
| 72 | 3.65 | ++ | − | − | − | + | ++ | ++ | ++ | |
| Lactic acid solution (pH 3.5) | + | − | − | − | − | − | − | − | ||
| Acetic acid solution (pH 3.5) | + | − | − | − | − | − | − | − | ||
| Ethyl alcohol solution (2% w/w) | − | − | − | − | − | − | − | − | ||
1)++, total inhibition; +, partial inhibition; −, no inhibition. 2)BC, Bacillus cereus ATCC14579; SA, Staphylococcus aureus ATCC6538; LM, Listeria monocytogenes ATCC51776; EF, Enterococcus faecalis ATCC19433; EC, Escherichia coli ATCC25922; SE, Salmonella Enteritidis obtained from the FDA; PA, Pseudomonas aeruginosa ATCC15522; CS, Cronobacter sakazakii ATCC29544.