Plating medium p H as a Factor in Apparent Survival of Sublethally Stressed Yeasts

Sublethally stressed cells of 9 of 10 species of yeast were recovered at maximum levels when potato dextrose agar was adjusted to approximatelyp H 8. The optimum forcandida utilis was at approximatelyp H 10. Atp H 3.5, as commonly employed with media selective for yeasts and molds, recovery of heat-stressed organisms ranged from essentially the same as at optimump H to levels of 1% or less of the maximum count. The extent to which this may be of practical significance in assessing the microbiological quality of food products remains to be determined.