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

Wheat sprouting in the field before harvest is a serious negative quality a ttribute. Even low levels of preharvest sprouting affect the economic value of the grain. Unreleased test lines of wheat should be screened for resist ance to preharvest sprouting. However, screening large numbers of rest line s is relatively time-consuming or expensive, depending on the existing meth od used. A new screening test for preharvest sprouting was developed and co mpared with the viscograph and cl-amylase activity (AAA) methods. The new m ethod used the activity of sprout-related elevation in alpha -amylase to pa rtially degrade added pregelatinized starch. The hydrolytic products were c entrifuged and the weight of the centrifugate was expressed as a percentage of the original weight of the added pregelatinized starch plus the origina l meal or flour weight. The result reflected the AAA on pregelatinized star ch (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 prehar vest sprouting than the AAA method. Three grinders to produce wheat meal we re compared for their effect on AAAPGS values. Flours produced slightly low er 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 leve ls of sensitivity to preharvest sprouting that could be detected by the AAA and AAAPGS methods were identified as areas of uncertainly, below which ve ry low levels of preharvest sprouting could not be differentiated from soun d, unsprouted background values. The new AAAPGS method was equally rapid an d will be more economical than the AAA method or the viscograph when used f or preharvest sprouting susceptibility of large numbers of samples.