Antimicrobial Agent of Aged Surface Ripened Cheese. I. Isolation and Assaya,b

Abstract
SUMMARY: Two types of soft surface ripened cheese become inhibitory to microbial growth after storage at 2 to 4° C for 8 weeks. The antimicrobial agent has been concentrated 4‐ to 16‐ fold by aqueous extraction and lyophilization or drying by a current of air. The total antimicrobial activity of aged surface ripened cheese of the described types was estimated to be at least 18.6 antimicrobial units per gram of product.The active principle inhibited growth and toxin production of type A Clostridium botulinum 62A, the growth of Staphylococcus aureus 223 and Bacillus cereus 800/58. Threshold subinhibitory amounts of the antimicrobial concentrates stimulated growth of these organisms.