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

A spectrophotometric method for determining soluble protein has been a pplied to the measurement of soluble nitrogen (SN) in micromalts from a barley breeding programme. A regression equation between wort SN val ues, measured by the Kjeldahl method, and the absorbance difference (A (215)-A(225)) of diluted wort samples was prepared and then used to pr edict SN levels of 353 worts produced from breeding material from a di verse genetic background. These data were highly correlated with those obtained from the Kjeldahl method (r = 0.952**). A second calibratio n equation relating wort absorbance at a single wavelength (A(215)) to Kjeldahl nitrogen data was able to predict wort SN values with equal accuracy compared with the relationship based on absorbance difference (A(215)-A(225)). Here, the correlation between the two data sets was r = 0.953** (n = 353). The spectrophotometric method is a rapid and s imple means of measuring wort SN in the large numbers of samples gener ated by barley breeders and the single wave-length measurement offers a particularly efficient method of screening the very small wort volum es produced from test tube-scale mashes.