SOURCES OF VARIATION FOR STARCH GELATINIZATION, PASTING, AND GELATIONPROPERTIES IN WHEAT

The starch of wheat (Triticum aestivum L.) flour affects food product quality due to the temperature-dependent interactions of starch with w ater during gelatinization, pasting, and gelation. The objective of th is study was to determine the fundamental basis of variation in gelati nization, pasting, and gelation of prime starch derived from seven dif ferent wheat cultivars: Kanto 107, which is a partial waxy mutant line , and six near-isogenic lines (NILs) differing in hardness. Complete p asting curves with extended 16-min hold at 93 degrees C were obtained using the Rapid Visco Analyser (RVA). Apparent amylose content ranged from 17.5 to 23.5%; total amylose content ranged from 22.8 to 28.2%. S tarches exhibited significant variation in onset of gelatinization. Ho wever, none of the parameters measured consistently correlated with on set or other RVA curve parameters that preceded peak paste viscosity. Peak paste viscosity varied from 190 to 323 RVA units (RVU). Higher pe ak, greater breakdown, lower final viscosity, negative setback, and le ss total setback were associated with lower apparent and total amylose contents. Each 1% reduction in apparent or total amylose content corr esponded to an increase in peak viscosity of about 22 and 25 RVU, resp ectively, at 12% starch concentration. Of the seven U.S. cultivars, th e lower amylose cultivars Penawawa and Klasic were missing the granule -bound starch synthase (GBSS; ADPglucose starch glycosyl transferase, EC 2.4.4.21) protein associated with the Waxy gene locus on chromosome 4A (Wx-B1 locus). Kanto 107 was confirmed as missing both the 7A and 4A waxy proteins (Wx-A1 and Wx-B1 loci). The hardness NIL also were sh own to be null at the 4A locus. Apparent and total amylose contents of prime starch generally corresponded well to the number of GBSS protei ns; although the hardness NIL tended to have somewhat higher amylose c ontents than did the other GBSS 4A nulls. We concluded that reduced qu antity of starch amylose due to decreased GBSS profoundly affects star ch gelatinization, pasting, and gelation properties.