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Cross-Linked Resistant Starch: Preparation and Properties¹

¹Contribution No. 02-198-J, Department of Grain Science and Industry, Kansas State University, Manhattan, KS. ²Research associate, Graduate School of Biotechnology, Laboratory of Food and Biomaterial Chemistry, Korea University, Seoul, S. Korea. ³Professor, Department of Grain Science and Industry, Kansas State University, Manhattan, KS, 66506. ⁴Corresponding author. Fax: 785-532-7010. E-mail: pas@wheat.ksu.edu.

Resistant starches (RS) were prepared by phosphorylation of wheat, waxy wheat, corn, waxy corn, high-amylose corn, oat, rice, tapioca, mung bean, banana, and potato starches in aqueous slurry (≈33% starch solids, w/w) with 1–19% (starch basis) of a 99:1 (w/w) mixture of sodium trimetaphosphate (STMP) and sodium tripolyphosphate (STPP) at pH 10.5–12.3 and 25–70°C for 0.5–24 hr with sodium sulfate or sodium chloride at 0–20% (starch basis). The RS₄ products contain ≤100% dietary fiber when assayed with the total dietary fiber method of the Association of Official Analytical Chemists (AOAC). In vitro digestion of four RS₄ wheat starches showed they contained 13–22% slowly digestible starch (SDS) and 36–66% RS. However after gelatinization, RS levels fell by 7–25% of ungelatinized levels, while SDS levels remained nearly the same. The cross-linked RS₄ starches were distinguished from native starches by elevated phosphorus levels, low swelling powers (≈3g/g) at 95°C, insolubilities (<1%) in 1M potassium hydroxide or 95% dimethyl sulfoxide, and increased temperatures and decreased enthalpies of gelatinization measured by differential scanning calorimetry.