Superheated Steam Modification of Finger Millet Starch for Application in 3D-Printed Foods for Dysphagic Patients

Abstract

Finger millet starch (FMS) is a sustainable and nutrient-rich biopolymer with potential in functional food applications. However, its native form exhibits poor thermal stability, limited swelling, and weak functional properties, hindering its effective utilization in value-added processing, especially for functional food development. To overcome these limitations, this study explores the use of superheated steam (SHS) to modify finger millet starch (FMS) for 3D printing of dysphagia-friendly foods. SHS treatment at 140-160 °C for 5-20 min altered starch granule morphology, increased crystallinity (25% to 37%), and enhanced solubility, swelling power, and pasting viscosities. The rheological analysis showed viscoelastic gels (G′ > G″), while tribology confirmed reduced friction, indicating improved swallowing comfort. Textural profiling revealed higher hardness (0.42 N) and cohesiveness (0.69), alongside reduced adhesiveness, matching requirements for dysphagia diets. Optimized 3D printing conditions (20% starch, 75 °C gelatinization, 5 mm nozzle diameter, 3 mm height) produced extrudable and structurally stable constructs. Fork pressure tests verified that SHS-treated samples particularly SS_140_20 met IDDSI Level 6 guidelines for soft and bite-sized foods. These findings highlight SHS as a green, additive-free modification strategy that enhances starch functionality and printability, enabling safe, personalized, and nutritionally relevant foods for swallowing-impaired individuals.