Impact of A/B-type granule ratio on reactivity, swelling, gelatinization, and pasting properties of modified wheat starch. Part I: Hydroxypropylation

The impact of granule type (A/B-type granule ratio) on the reactivity and physical properties of chemically-modified wheat starch was investigated. Waxy and normal wheat starches were fractionated into highly-purified A- and B-type granule fractions, and reconstituted into fractions possessing pre-defined A/B-type granule ratios (weight basis). Starch granule fractions were derivatized with either propylene oxide (PO) or PO analog (POA), and assessed with respect to molar substitution (MS), swelling, gelatinization, and pasting properties. For POA (MS < 0.025) and PO (MS ≈ 0.1) starch derivatives, no differences in the relative reactivities of A-type and B-type granules or among the reconstituted wheat starches of varied A/B-type granule contents were observed within a genotype. Despite the similar reactivities of reconstituted wheat starch fractions possessing varied A/B-type granule contents, variations in swelling, gelatinization, and pasting properties were observed across the modified reconstituted starch granule fractions. Thus, substitution did not completely eradicate inherent property differences observed between unmodified reconstituted wheat starch granule fractions (based on differing A/B-type granule contents).