From Liquid Feeds to Functional Powders: Process Engineering, Quality, Valorisation and Emerging Innovations in Spray Drying of Fruits and Vegetables

Abstract

Spray drying is an effective and scalable technique for transforming highly perishable fruit and vegetable juices, extracts and processing by-products into stable powders with improved handling, storage, convenience and application potential. This review synthesises recent advances in spray drying of fruit and vegetable products, moving beyond a description of the drying process towards an integrated appraisal of process engineering, formulation strategies, powder quality, storage stability, by-product valorisation and emerging technologies. The literature indicates that drying temperature, feed flow rate, airflow rate, atomisation conditions and carrier type and concentration collectively determine powder recovery and key quality attributes, including moisture content, water activity, hygroscopicity, colour, solubility, bulk density, flowability and reconstitution behaviour. Maltodextrin and gum arabic remain widely employed carrier agents because they improve powder formation, reduce stickiness and moisture uptake and support storage stability, although their effectiveness varies with feed composition and processing conditions. Water activity below 0.30 is generally associated with improved microbiological and physicochemical stability of fruit and vegetable powders. Conventional spray drying nevertheless remains constrained by thermal degradation of heat-sensitive compounds, wall deposition, stickiness, caking and losses of valuable bioactive components. Emerging approaches, including vacuum, ultrasound-assisted, dehumidified air, electrostatic, nano and pulse combustion spray drying, provide opportunities to improve heat and mass transfer, drying efficiency, powder recovery and bioactive retention. Spray drying of peels, pomace, seeds and other processing residues further expands opportunities for waste reduction and value-added functional ingredients. Future priorities include integrated optimisation of process and formulation variables, predictive and data-driven process control, sustainable carrier systems, energy-efficient drying, long-term storage evaluation and pilot- and industrial-scale validation to facilitate the commercial development of stable, functional and economically viable fruit and vegetable powders.