NEAR INFRARED REFLECTANCE ANALYSIS OF WHOLE HOP CONES

Abstract

Near infrared (NIR) reflectance spectroscopy has been evaluated for the analysis of whole hops from the 1985 and 1986 U.K. crops. Good agreement, with a correlation coefficient (r) of 0·963, was obtained between reference and NIR methods for moisture measurement. A standard error of prediction (SEP) between 0·27–0·33% was achieved over the two years. Good correlations, up to 0·949 between methods, were achieved for Lead Conductance Value (SEP 0·73%). While this accuracy is not acceptable for commercial transactions the measurement could be useful for screening purposes, for example, plant breeding or monitoring of crop ripening. Similar calibrations have been achieved for α-acids (r 0·940, SEP 0·74%) and β-acids (r 0·910, SEP 0·43%). A less accurate calibration has been developed for hop oil analysis (r 0·803, SEP 0·17 ml/100g). Since no sample preparation is required, the NIR technique provides a rapid and non-destructive method for measuring all these constituents simultaneously.