Interrelationship Between Water Activity, Temperature and 5.5 Percent Oxygen on Growth and Enterotoxin A Secretion by <i>Staphylococcus aureus</i> in Precooked Bacon

Abstract

ABSTRACT The limiting water activity (a w ) for the growth of S. aureus A‐100 sealed in cans at an oxygen concentration of 5.5% was 0.87 at 37°C and 0.91% at 20°C, values intermediate to those obtained previously for aerobic and anaerobic storage. Maximum populations attained at 37°C and 20°C were equal and once achieved population levels declined more slowly at 20°C than at 37°C. Enterotoxin A production was detected for population levels exceeding 10 6 CFU/g bacon and were 100 ng/g bacon at 37°C and 16 ng/g bacon at 20°C. It is suggested that while temperature and oxygen are important considerations, a w , being the main parameter in controlling microbial growth, should be measured directly rather than depending on indirect measurements such as the moisture‐salt ratio.