Quick Reflectometric Determination of Total Glucosinolate Contents in Trade Samples

Abstract

In the framework of standardized cultivation which was performed at about 70 farms located allover the Federal Republic of Germany, three and four 00-rapeseed varieties, respectively, were produced each from a common seed source during two years, 1985 and 1986. Seed samples were taken during harvest and sent to Gottingen for analysis of their glucosinolate contents. The applied method was based on an inactivation of the endogenous myrosinase and a liberation of the glucose moiety from the glucosinolate molecule by standardized myrosinase addition. Measurement occurred by Boehringer GLUCOTEST paper and a pocket reflectometer. The results prove the method to be valid for a quick, cheap and reliable discrimination between samples derived from the traditional 0-versus the new 00-varieties of rapeseed with a high and low content of glucosinolates, respectively. The same holds true for several other analytical methods elaborated elsewhere. None of these quick tests, however, has sufficient precision and accuracy for an analysis of samples having a content of glucosinolates close to the threshold value of separation between 00- and 0-varieties. For such materials, which in fact may occur rather often in practice because of volunteer rapeseed admixtures in the fields, an accurate determination will never escape the tedious procedure of one of the more sophisticated and precise methods of quantitative glucosinolate analysis.