Optimization of kilning progress for equilibrating multiple parameters that strictly affect malt flavour and sensory evaluation

Abstract

This study developed a multiple-parameter equilibration-based kilning technology optimization method with a Box–Behnken factorial design and response surface methodology, assessing 10 kinds of indexes from multiple perspectives, including malt stale flavour, malty aroma and sensory evaluation, simultaneously. The results indicated that lipoxygenase (LOX) activity, nonenal potential and sensory score had a tendency to decline, while 4-hydroxy-2,5-dimethyl-3 (2H)-furanone, thiobarbituric acid (TBZ) and stale aldehydes increased with the rise in kilning temperature, the extension of kilning time and withering time. The corresponding second-order mathematical models were established for predicting each parameter. Among them, p-values of a model equation of LOX activity, nonenal potential, 4-hydroxy-2,5-dimethyl-3(2H)-furanone, TBZ, methional and furfural were all <0.05 and R2 values were >0.9, which indicated that these equations had higher significance and that data in excess of 90% could be explained. Subsequently, the numerical optimization of kilning technology was carried out for balancing these positive or negative parameters and the optimum kilning temperature, kilning time and withering time were found to be 86.35 °C, 3.19 h and 14.00 h, respectively. Compared with the values of the original response, the values of the 10 parameters were optimized from 2.2 to 65.2%. This method offers an ability to monitor malt characteristics to obtain higher quality malt. Further, the method will help maltsters and brewers to comprehensively understand malt with different cultivar genetics and growing environments. Copyright © 2016 The Institute of Brewing & Distilling.