Foaming Agents in Foam Mat Drying of Fruits: Mechanisms, Effectiveness, and Functional Applications – A Review

Foam mat drying is a promising technique for producing high-quality, shelf-stable fruit powders, particularly from heat-sensitive, viscous, and underutilized fruits. This review critically examines the roles and effectiveness of food-grade foaming agents, including proteins, carbohydrates, and hydrocolloids, in enhancing foam formation, stability, and overall drying efficiency. Protein-based agents such as egg albumin, whey protein isolate, and soy protein isolate provide excellent foam expansion and structural integrity. Carbohydrate-based compounds like maltodextrin, pectin, and modified starch primarily function as stabilizers, improving viscosity and nutrient retention. Hydrocolloids such as methylcellulose, carboxymethyl cellulose, guar gum, and xanthan gum further strengthen foam structure and enhance the rehydration properties of the resulting powders. Synergistic combinations of these foaming and stabilizing agents tailored to specific fruit matrices significantly improve powder quality, solubility, and preservation of bioactive compounds. Despite advancements, key challenges remain, including the development of novel, plant-based, and allergen-free alternatives, limited application to underutilized fruits, and a lack of techno-economic and environmental sustainability assessments. This review provides a consolidated framework to guide future research and industrial applications aimed at optimizing foam mat drying for efficient, value-added, and sustainable fruit processing.