Fate of Escherichia coli and Kluyveromyces marxianus contaminants during storage of Greek-style yogurt produced by centrifugation or ultrafiltration

The production of Greek-style yogurts requires more processing steps than traditional yogurt, which increases the possibility of microbial contamination by pathogens or spoilage organisms. The growth and survival during storage of two microbial contaminants (Escherichia coli and Kluyveromyces marxianus) in Greek-style yogurt, produced by centrifugation or ultrafiltration, was compared with that in regular stirred yogurt. E. coli strain ATCC® BAA-1430™ was shown to be a suitable surrogate for pathogenic O157:H7 in yogurt. The increased buffering capacity of the Greek-style yogurts produced from ultrafiltered milk led to lower E. coli viability during storage. On the other hand, the Greek-style yogurt seems to promote faster growth of the dairy yeast K. marxianus at a storage temperature of 4 °C.