IMPEDIMETRIC METHOD FOR SELECTIVE ENUMERATION OF SPECIFIC YOGURT BACTERIA WITH MILK-BASED CULTURE MEDIA

The suitability of the impedimetric method for the selective enumerati on of specific microorganisms, particularly yoghurt bacteria, Streptoc occus thermophilus and Lactobacillus delbrueckii subsp bulgaricus, was investigated in comparison with the standard plate count technique. A series of samples were analyzed by using new milk-based culture media (milk added with saccharose and acidified milk) for the impedance tec hnique, whereas for the conventional counting method M17 and MRS cultu re media were applied. It was found that the milk-based culture media are suitable for the selective enumeration of specific yoghurt bacteri a: the values detected by the impedimetric measurement (Bactometer ins trument) and those resulting from the standard plate count showed a go od correlation. The suggested milk-based culture media are shown to be suitable for the selective counting of yoghurt bacteria when applied in the impedimetric technique. Furthermore, since the bacterial counti ng may be determined within 12 h, the impedimetric method is also fast er than the conventional method.