222-nm far-UVC/H₂O₂ photodegradation as a versatile and effective tool for depolymerizing starch-rich materials and...

Starch liquefaction is a highly energy-intensive process in the food industry due to requirements for high-temperature gelatinization followed by α-amylase hydrolysis (90-100 °C). This study introduces 222-nm far-ultraviolet C (far-UVC)/H₂O₂ photodegradation as an innovative non-thermal alternative to enzymatic liquefaction. A UV/H₂O₂ system (irradiance 4.42 mW·cm^-2) was set up to liquefy wheat starch (WS) and rice powders (RP), and 222-nm far-UVC was selected as the radiation source over 254-nm UVC with its better ability to induce ·OH radicals and higher levels of yielded total soluble saccharides (TSS) in photodegraded WS and RP (PDWS, PDRP). Far-UVC/H₂O₂ was benchmarked against α-amylase on starch depolymerization, and H₂O₂ concentrations of 0.68% and 0.85% were initially confirmed, producing PDWS and PDRP with comparable TSS contents to enzymatically degraded (ED) rivals. Far-UVC/H₂O₂ demonstrated effective starch depolymerization via glycosidic bond cleavage, evidenced by reduced molecular weight and viscosity, along with microstructural variations. Although occurrences of carbonyl and carboxyl groups in PDWS and PDRP indicated minor oxidations by far-UVC/H₂O₂, wort mashed with them exhibited sugar profiles and fermentability equivalent to their ED-counterparts under the optimized condition (80 °C, 20 min, 0.68% H₂O₂), showcasing far-UVC/H₂O₂ as an effective and sustainable strategy for starch liquefaction, remarkably reducing thermal energy footprints.