Foam layer drying of tropical fruits: Physicochemical, functional, and microbiological characterization of powders

Foam layer drying is an alternative to conventional dehydration methods due to its ability to reduce thermal damage and preserve bioactive compounds of different food matrices. This study aimed to evaluate the physical, chemical, and microbiological characteristics of tropical fruit powders (watermelon, guava, pineapple, and acerola) obtained by foam layer drying using a combined system of powdered egg white albumin and carboxymethylcellulose. The fruit pulps were processed, foamed, and dried at 68 °C for 6 h, and the resulting powders were characterized in terms of hygroscopicity, density, flowability, water and oil retention capacity, color, moisture, water activity, phenolic and carotenoid compound profiles, antioxidant capacity, microbiological quality, and antimicrobial activity. The powders showed low moisture (2.8-3.6%) and water activity (0.18-0.22), excellent flowability, low hygroscopicity (1.28-3.66%), and favorable functional properties. High levels of phenolic and carotenoid compounds were preserved, resulting in pronounced antioxidant activity. All samples met the microbiological standards stipulated in the legislation, showing an absence of pathogenic bacteria and low microbial counts. Limited and selective antimicrobial activity was observed in the hydroethanolic extracts. Overall, foam drying proved to be an efficient and robust technology for the production of tropical fruit powders rich in bioactive compounds, with great potential for application as functional ingredients.