Modern scientific methods are required to enforce the Federal Food, Drug, and Cosmetic Act. Laws to ensure the wholesomeness of foods and the safety and efficacy of drugs would be impractical without reliable methods of laboratory analysis to determine whether products are up to standard_The principal authority relied on for laboratory methods is "official Methods of Analysis of the Association of Official Analytical Chemists." From HHS Publication No. (FDA)86-1054.
In the definitions, §110.3(n), it says "Safe-moisture level is a level of moisture low enough to prevent the growth of undesirable microorganisms in the finished product under the intended conditions of manufacturing, storage, and distribution." The maximum safe moisture level for a food is based on its water activity (aw). An aw will be considered safe for a food if adequate data are available that demonstrate that the food at or below the given aw will not support the growth of undesirable microorganisms.
§110.3(r), Water activity (aw) is a measure of the free moisture in a food and is the quotient of the water vapor pressure of the substance divided by the vapor pressure of pure water at the same temperature.
§110.80(b)(2) All food manufacturing, including packaging and storage, shall be conducted under such conditions and controls as are necessary to minimize the potential for the growth of microorganisms, or for the contamination of food. One way to comply with this requirement is careful monitoring of physical factors such as time, temperature humidity, aw, pH, pressure, flow rate, and manufacturing operations_
§110.80(b)(4) Measures such as sterilizing, irradiating, pasteurizing, freezing, refrigerating, controlling pH or controlling aw that are taken to destroy or prevent the growth of undesirable microorganisms, particularly those of public health significance, shall be adequate under the conditions of manufacture, handling, and distribution to prevent food from being adulterated within the meaning of the act.
§110.80 (b)(14) Food such as, but not limited to, dry mixes, nuts, intermediate moisture food, and dehydrated food, that relies on the control of aw for preventing the growth of undesirable microorganisms shall be processed to and maintained at a safe moisture level. Compliance with this requirement may be accomplished by any effective means, including employment of
one or more of the following practices:
(i) Monitoring the aw of food
(ii) Controlling the soluble solids-water ratio in finished food
(iii) Protecting finished food from moisture pickup, by the use of a moisture barrier or by other means, so that the aw of the food does not increase to an unsafe level.
Reference: 4-1-96 Edition CFR, Part 110-Current "Good Manufacturing Practice in Manufacturing, Packing, or Holding Human Food".