Sustainable route for the production of starch submicrocrystals: Effect of α-amylase combined with ohmic heating on A-, B-, and C-type starches.

This study investigates a sustainable route for the production of submicron starch through a combined approach of ohmic heating (OH) treatment and enzymatic hydrolysis with α-amylase. The effects of electric field frequency (50 Hz, 10 kHz, and 20 kHz) during OH pretreatment were evaluated in type A (corn), type B (cassava), and type C (carioca bean) starches. The results demonstrated that OH pretreatment effectively disrupted the granular structure, increased enzymatic accessibility, and promoted the selective degradation of amorphous regions. The synergistic effect of OH and α-amylase hydrolysis was starch-type dependent: for B-type, B50 + E increased crystallinity from 53.2% to 57.1% (p < 0.05); for A-type, AN+E (48.1%) and A20k + E (50.1%) both increased crystallinity versus native (AN: 40.4%) (p < 0.05); for C-type, C10k (48.7%) increased crystallinity versus native (CN: 43.7%) (p < 0.05), while C10k + E (44.6%) did not differ from native (p > 0.05). This combined approach reduced particle size to the submicron range (≈485-662 nm) and significantly modulated functional properties, including digestibility, gelatinization behavior, and thermal stability. The optimal OH frequency was starch-type dependent: enzymatic hydrolysis alone or 20 kHz for type A, 50 Hz for type B, and 10 kHz for type C. This sustainable and efficient dual-modification strategy represents a promising alternative to conventional acid hydrolysis for production of submicron starch, enabling the design of starch-based materials with tailored structural and functional properties and reduced environmental impact.