Starch was dually chemically modified for developing food-grade ingredients of lower digestibility and their properties were compared to those of single modified and native starches. Hydroxypropylation with propylene oxide (HP) followed by esterification with octenylsuccinic anhydride (OSA) of potato starch (P-native) produced derivatives with lower digestibility than esterification solely with OSA. The dextrose equivalent, maltose and glucose contents, which were used as the main indicators for in vitro digestion, were lower for modified starches. P-HP0.2-OSA0.0200 derivative was the least digestible; the glucose and maltose contents were lowered by 28.3 and 42.1% compared to P-native. The aggregation behavior of enzymatically hydrolyzed starch derivatives was studied in aqueous solution by employing the fluorescence probe and dynamic light scattering techniques. The critical aggregation concentration for OSA modified and dually modified starches varied from 1.2 to 3 g/L and from 0.125 to 0.48 g/L, respectively, depending on the degree of OSA substitution. The study showed that above a critical concentration the hydrolyzates of modified starches tend to form the aggregates with different properties depending both on the degree of OSA substitution and chemical structure.
Keywords: Critical aggregation concentration; Dually modified; Fluorescence probe technique; Potato starch.