Beyond Encapsulation Efficiency: Designing Spray-Dried Botanical Extract Powders for Storage Stability in Hot and Humid Markets

Spray drying with carbohydrate, gum and protein wall materials is the dominant route for converting botanical extracts into powders for supplements and functional foods. Most studies, and recent reviews of wall materials, judge success by encapsulation yield, encapsulation efficiency and particle morphology measured immediately after drying. For products sold in hot and very humid regions, where stability testing is performed at 30 degrees Celsius and 75 per cent relative humidity, these measures say little about shelf life. This narrative review reframes wall-material selection around storage performance. It explains how water sorption and the glass transition determine stickiness, caking and chemical degradation; compares maltodextrins, gum arabic, starches and proteins by their stability-relevant properties, including halal and supply considerations; and examines what encapsulation efficiency, moisture content and flow indices do and do not show. A recent elderberry study is used as a worked example: its preferred powder had a Carr index of about 27 and a Hausner ratio of 1.38, classed as poor flow by pharmacopoeial criteria, and no storage test was performed. A testing sequence combining sorption isotherms, glass transition measurement and climatic-zone storage in the final pack is proposed, with a minimum reporting standard.