Characterization of resistant waxy maize dextrins prepared by simultaneous debranching and crystallization followed by acidic or enzymatic hydrolysis

Resistant dextrins (RD) were prepared by simultaneous debranching and crystallization with waxy maize starch at 50 °C for 7 days, followed by the hydrolysis using an acid (3.16 M sulfuric acid) or ɑ-amylase (5% based on starch solids) for 24 h. The crystallinity, thermal transition, morphology, and in vitro digestibility of the hydrolyzed RDs were analyzed. The RD hydrolysates showed typical A-type crystalline patterns under X-ray diffraction with increases in crystallinity and thermal stability compared to the unhydrolyzed counterparts. The RD crystals were obtained as nano-sized particles by the hydrolysis, which readily aggregated while drying. Based on the in vitro digestibility test, the enzyme-resistant fraction of the hydrolyzed RDs was greater than the unhydrolyzed one by 5–10%. Heating in a boiling water-bath (15 min) decreased the enzyme-resistant fraction to less than 50%, while the hydrolysis raised the fraction by 10–15%. The hydrolysis could be used in the preparation of nano-sized RD with increased crystallinity and resistance to the digestion.