Water Activity a Key Parameter in a New Shelf Stable Baked Good Standard
NOW CERTIFICATION to ANSI/NSF Standard 75 ensures that certain baked goods will not support the rapid and progressive growth of potentially hazardous bacteria. This is accomplished by reformulation to a water activity value of 0.85 or less and/or a pH level of 4.6 or less, or challenge testing with inoculation of specific strains of bacteria. These products can be stored at ambient temperatures for a specified period of time, saving costly refrigeration space without endangering the public health and safety.
Standard 75 was developed based on the current FDA Food Code definition of nonpotentially hazardous foods. Non-potentially hazardous foods do not support the rapid and progressive growth of infectious or toxigenic microorganisms. Every microorganism has a water activity level below which it cannot grow. Water activity, not water content, determines the lower limit of available water for microbial growth. The lowest aw at which the vast majority of food spoilage bacteria will grow is about 0.90. Staphylococcus aureus under anaerobic conditions is inhibited at an aw of 0.91, but aerobically the aw level is 0.86. The minimum aw for toxin production is generally higher than the minimum aw growth level.
Water activity controls microbial growth and allows the product to be safely stored without refrigeration. A recent study by NSF shows a 40% increase in product sales when merchandise is stored in high-traffic, non-refrigerated display units. Today, desserts such as soft pies and filled pastries face greater regulatory scrutiny when displayed without refrigeration. ANSI/NSF Standard 75 provides test methods and evaluation criteria (i.e. critical aw limit) to determine that a product does not require refrigeration for safe storage.