Effect of Drying Methods on the Physical and Surface Properties of Blueberry and Strawberry Fruit Powders: A Review

Strawberries and blueberries are globally recognized for their dense nutritional profile, bioactive compounds, and health-promoting properties. Yet, their perishability and seasonality limit their availability, stability, and functionality in food and nutraceutical formulations. Drying technologies, particularly spray drying and freeze drying, are effective preservation strategies that convert fresh berries into stable, shelf-ready powders. However, the high sugar content, low glass transition temperature (Tg), and hygroscopic nature of berry matrices pose significant challenges in maintaining powder flowability, preventing caking, and ensuring structural integrity during processing, storage, and transportation. This review examines the physicochemical and surface properties of strawberry and blueberry powders as influenced by the drying method, environmental conditions, and carrier selection (e.g., maltodextrin, gum arabic, and whey proteins). Emphasis is placed on glass transition phenomena, moisture sorption behavior, and surface composition as determinants of physical stability and shelf life. The roles of water activity (aw), particle morphology, and interparticle interactions are analyzed in the context of formulation design and powder performance. Analytical techniques in characterizing bulk properties for the amorphous structure and sorption kinetics and probing surface properties of powders are crucial for understanding interactions with water, assessing flow, caking, sintering, and dissolution. By integrating insights from food physical chemistry and materials surface properties, this review provides a framework for the rational design of berry-based powders with improved handling, stability, and bio-functionality. The findings have direct implications for scalable production, global distribution, and the development of functional ingredients aligned with health and wellness priorities worldwide.