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

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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.

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