Resistant starches from amylose mutants of corn by simultaneous heat-moisture treatment and phosphorylation

Foods with increased levels of slowly digestible starch (SDS) and resistant starch (RS) are thought to provide nutritional benefits for humans. High-amylose (∼70%) corn starch (Hylon VII) was simultaneously heat-moisture treated and phosphorylated/cross-linked with a 99/1 (w/w) mixture of sodium trimetaphosphate/sodium tripolyphosphate (STMP/STPP) at initial pH 11.5. Modeling was done to determine the effects of moisture (21–49% of total mixture) and STMP/STPP (2.8–11.2% of dry starch, sb) on the phosphorus (P) content of the modified starch and its level of RS after cooking. Reacting Hylon VII with 10% of STMP/STPP (sb) at 45% moisture for 4 h at pH 11.5 and 110 °C gave a product with 0.39% P, 14% SDS, and 43% RS in the freshly cooked starch compared to 0.03% P, 14% SDS, and 25% RS for untreated Hylon VII. The modified Hylon VII had 90% dietary fiber content and a higher gelatinization temperature of ∼20 °C. Hylon V, waxy, and normal corn starches were modified similarly to ∼0.4% P, and the raw and cooked modified starches contained, respectively, 73, 43, and 42% and 44, 32, and 32% of combined SDS and RS.