Water Activity

Margaret Balfour, Managing Director of Integrity Compliance Solutions did a Linkedin post on Water Activity. She said, “water activity (Aw) is a common method to manage microbial growth in foods. Water activity is defined as the partial vapor pressure of water in a substance divided by the standard state partial vapor pressure of water. All microorganisms require water to live – at varying levels. By manipulating the Aw of a food, we can control the growth of the target pathogen. The Aw of distilled water is 1.0, raw meat 0.99, milk and juice 0.97, saturated NaCl (salt) solution 0.75, dried fruit 0.6, indoor air 0.5-0.7 and honey 0.5 – 0.7. The physical presence of water itself does not support growth unless the water is chemically available to the pathogen. By adding ingredients such as salt and sugar, we can manipulate the Aw and extend shelf life.”

She then asked a very provocative question. “The challenge is what to do when consumers don’t want any added sugar, salt, preservatives etc.!”

(Ref. Barbosa-Canovas App. D 2007).

Featured Image: https://www.metergroup.com/food/articles/introduction-to-water-activity/