Molecular structure of different prepared pyrodextrins and the inhibitory effects on starch retrogradation

Pyrodextrins with different molecular size were prepared by dry heating native corn starch with and without hydrochloric acid (HCl) at 180 °C for 0.5, 3, and 5 h. Those with HCl treatment displayed much smaller molecular size, narrower size distribution, and higher proportion of the chains with the degree of polymerization (DP) ~24-400 than the counterparts without HCl treatment. Pasting and rheological tests showed that the addition of pyrodextrins with HCl treatment displayed lower overall and setback viscosity, and reduced gel development and gel strength in comparison of those without HCl treatment. Differential scanning calorimetry (DSC) and wide-range X-ray (WXRD) data suggested that the pyrodextrin sample prepared by heating native starch with HCl at 180 °C for 5 h (A₅) displayed the most effective inhibition on starch long-term retrogradation. This study could supply a pathway by applying pyrodextrins to both increase nutrition value and retard starch retrogradation for bakery and beverage industry.