Nonthermal starch hydrolysis using ultra high pressure: I. Effects of acids and starch concentrations

Abstract

Corn starches with 2 mol/l hydrochloric acid (HCl), 2 mol/l sulfuric acid (H 2SO 4) and 2 mol/l oxalic acid (C 2H 2O 4) were pressurized at 600 MPa for 30 min. Corn starch with C 2H 2O 4 formed a gel after ultra-high-pressure (UHP) treatment. Corn starch with HCl showed partial disintegration but starch with H 2SO 4 maintained its shape. Corn starch with HCl showed higher (0.42–0.47) degree of hydrolysis compared to starch with C 2H 2O 4 (about 0.14) and H 2SO 4 (0.13–0.14) regardless of increasing starch concentration up to 20 g/100 g sample. Main component of starch hydrolysate was maltose for HCl and oligosaccharides for H 2SO 4 and C 2H 2O 4. Crystallinity of starch with HCl decreased with decreasing starch concentration as observed by both differential scanning calorimetry (DSC) and X-ray diffraction. Therefore, UHP can be used for nonthermal starch hydrolysis and HCl would be a good catalyst for UHP starch hydrolysis compared to H 2SO 4 and C 2H 2O 4. This work provides a potential of nonthermal UHP processing for new starch hydrolysis method.