Deconstructing changes in the stability of Powders and Spices with Water Activity

Low moisture food ingredients are utilized by most food manufacturers because of their easy handling and longer shelf life. Examples of low moisture ingredients include milk powder, flour, sugars, starches, and spices. When considering the stability of powders and spices, the most common mode of failure is likely caking or clumping because it makes them difficult to handle and impacts production efficiency [1]. However, an additional concern for powders and spices which has more recently gained attention due to several product recalls originating from low moisture ingredients is microbial safety [2,3]. While it may seem strange to discuss the microbial safety of ingredients whose water activities fall well below the lower limit for microbial growth, it is still possible to for low moisture ingredients to be carriers of microorganisms. Spices are a unique type of low moisture ingredient that are defined as products derived from vegetables or mixtures thereof which are free from other material and are used to provide flavorings, seasoning, and aroma to foods. Spices are strong antioxidants and have other beneficial qualities as well. They have
traditionally been processed and traded as dry products, usually dried by the sun [4]. The quality indices of spices are focused on maintaining safety, preventing adulteration, maintaining flavor profile, and assuring easy handling. Spices are particularly susceptible to changes in their organoleptic profile due to chemical reactions that produce off colors, flavors, and odors. As with other low moisture ingredients, spices have been increasingly targeted as potential carries of microorganisms. There may be a tendency to consider water activity testing of powders and spices unnecessary because they are low moisture. However, all the common modes of failure for powders and spices are related to and can potentially be controlled by water activity. Identifying and maintaining an ideal water activity range for the stability of powders and spices may be the easiest and most effective way to maximize their utility and shelf life. The objective of this whitepaper is to discuss the theory of water activity and describe how to identify the critical water activity that will limit powder and spice modes of failure including: glass transition, caking and clumping, chemical degradation, and microbial safety.


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