Hygienic design requirements for spray drying operations

Spray drying is used extensively in the food and food-related industries for the manufacture of a wide range of products in dry particulate form both as powders and agglomerates. Spray drying produces these products by atomizing a liquid formulation within a suspended particle drying system. Therefore, the spray-drying process features moist particles existing both in an airborne state and as a semi-dried product present at the walls of the drying chamber, ducts, and associated powder handling components. The presence of any partially dried product within the warm components of the drying system over an extended period of time can result in microbial growth. This presents a possible hygienic risk in such cases where products are sensitive to this form of contamination. With the increasing use of spray drying in the above-mentioned industries, there is greater focus on hygienic spray dryer design and the operating considerations that need to be taken into account, so that hygienic processing can be economically achieved. This is irrespective of whether a hygienic evaluation involves an existing spray dryer or the engineering phase of a new plant. This article addresses industrial personnel associated with a hygienic manufacturing operation involving spray drying and offers guidelines for assessing whether an existing or planned new spray dryer meets hygienic engineering/design criteria for economic operation without risks of powder quality degradation through contamination.