|Sources of variation for starch gelatinization, pasting and gelation properties in wheat. Cereal Chemistry 74:63-71
|Zeng,M., Morris,C.F., Batey,I.L. and Wrigley,C.W.
|The starch of wheat (Triticum aestivum
L.) flour affects food product quality due to the temperature-dependant interactions
of starch with water during gelatinization, pasting, and gelation. The objective
of this study was to determine the fundamental basis of variation in gelatinization,
pasting, and gelation of prime starch derived from seven different wheat cultivars:
Kanto 107, which is a partial waxy mutant line, and six near-isogenic lines
(NILs) differing in hardness. Complete pasting curves with extended 16-min hold
at 93° C were obtained using the Rapid Visco Analyzer (RVA). Apparent
amylose content ranged from 17.5 to 23.5%; total amylose content ranged from
22.8 to 28.2%. Starches exhibited significant variation in onset of gelatinization.
However, none of the parameters measured consistently correlated with onset
or other RVA curve parameters that precede peak paste viscosity. Peak paste
viscosity varied from 190 to 323 RVA units (RVU). Higher peak, greater breakdown,
lower final viscosity, negative setback, and less total setback were associated
with lower apparent and total amylose contents. Each 1% reduction in apparent
or total amylose content corresponded to an increase in peak viscosity of about
22 and 25 RVU, respectively, at 12% starch concentration. Of the seven U.S.
cultivars, the lower amylose cultivars Penawawa and Klasic were missing the
granule-bound starch sythase (GBSS; ADPglucose starch glycosyl transferase,
EC 18.104.22.168) 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 shown to be null at the 4A
locus. Apparent and total amylose contents of prime starch generally corresponded
well to the number of GBSS proteins; although the hardness NIL tended to have
somewhat higher amylose contents than did the other GBSS 4A nulls. We concluded
that reduced quantity of starch amylose due to decreased GBSS profoundly affects
starch gelatinization, pasting, and gelation properties.
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