RAPID SPECTROPHOTOMETRIC MEASUREMENT OF SOLUBLE NITROGEN IN MICROMALTS FROM A BARLEY BREEDING PROGRAMME

Abstract

A spectrophotometric method for determining soluble protein has been applied to the measurement of soluble nitrogen (SN) in micromalts from a barley breeding programme. A regression equation between wort SN values, measured by the Kjeldahl method, and the absorbance difference (A218‐A228|) of diluted wort samples was prepared and then used to predict SN levels of 353 worts produced from breeding material from a diverse genetic background. These data were highly correlated with those obtained from the Kjeldahl method (r = 0.952). A second calibration equation relating wort absorbance at a single wavelength (A218) to Kjeldahl nitrogen data was able to predict wort SN values with equal accuracy compared with the relationship based on absorbance difference (A218‐A228)‐ Here, the correlation between the two data sets was r = 0.953 (n = 353). The spectrophotometric method is a rapid and simple means of measuring wort SN in the large numbers of samples generated by barley breeders and the single wave‐length measurement offers a particularly efficient method of screening the very small wort volumes produced from test tube‐scale mashes. 1995 The Institute of Brewing & Distilling