Landraces of wheat may harbor wide diversity in quality-related traits, yet they have been little utilized to improve modern wheat varieties for major end uses such as noodles. Screening for starch physical properties in wheat breeding programs may provide valuable information on the suitability of genotypes for noodle manufacture. The pasting or viscoamylograph characteristics, especially the peak viscosity and the rate of viscosity breakdown after gelatinization, have been widely used to predict the eating quality of Japanese white salted noodles (WSN) and also applied to Chinese yellow alkaline noodles (YAN). We investigated the pasting properties of purified wheat starch and wholemeal from 21 Iranian landrace accessions and five standard cultivars, in water and in salt and alkaline conditions. The peak viscosity of starch with added water or 2% salt and at as-is or alkaline pH (pH 11) were found to be significantly correlated with each other. The results obtained were compared with the pasting profiles of wholemeal under the same treatment conditions. The peak viscosity of wholemeal was significantly correlated with that of starch, especially when 0.5 mM silver nitrate was used to suppress the effect of α-amylase. It was confirmed that wholemeal may be used instead of starch during rapid screening of wheat genotypes when sample availability is limited, but wide differences in starch content in unadapted material, such as landraces, will reduce the accuracy of the results. When wholemeal is to be used for screening wheat for desirable end use quality, it is preferable to always use an amylase inhibitor like silver nitrate to eliminate the effect of endogenous amylases, even in nonsprouted material. The differences in pasting profiles resulting from alkaline versus nonalkaline conditions indicate that whenever YAN quality is of particular importance, screening under high pH should also be conducted.
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|Published - 1996