Detection of wheat preharvest sprouting using a pregelatinized starch substrate and centrifugation

Wheat sprouting in the field before harvest is a serious negative quality attribute. Even low levels of preharvest sprouting affect the economic value of the grain. Unreleased test lines of wheat should be screened for resistance to preharvest sprouting. However, screening large numbers of rest lines is relatively time-consuming or expensive, depending on the existing method used. A new screening test for preharvest sprouting was developed and compared with the viscograph and cl-amylase activity (AAA) methods. The new method used the activity of sprout-related elevation in alpha -amylase to partially degrade added pregelatinized starch. The hydrolytic products were centrifuged and the weight of the centrifugate was expressed as a percentage of the original weight of the added pregelatinized starch plus the original meal or flour weight. The result reflected the AAA on pregelatinized starch (AAAPGS) as a measure of the degree of preharvest sprouting. The AAAPGS test had less standard error and was more sensitive at low levels of preharvest sprouting than the AAA method. Three grinders to produce wheat meal were compared for their effect on AAAPGS values. Flours produced slightly lower AAAPGS values than meals, but the coefficients of variation of each were comparable and both were less than that of the AAA method. The lowest levels of sensitivity to preharvest sprouting that could be detected by the AAA and AAAPGS methods were identified as areas of uncertainly, below which very low levels of preharvest sprouting could not be differentiated from sound, unsprouted background values. The new AAAPGS method was equally rapid and will be more economical than the AAA method or the viscograph when used for preharvest sprouting susceptibility of large numbers of samples.