Kinetics of sensory quality changes in soymilk during thermal processing, by parametric and non-parametric data analyses

Abstract

Soymilk was subjected to various heat treatments at 90, 120 and 140 °C for various lengths of time. The colour and flavour of the soymilk samples were evaluated by a sensory panel consisting of eight semi-trained assessors on (1) a 9-unit hedonic scale, with analysis based on the assumption that the units are equidistant, and (2) a 15-point hedonic ‘Smiley’ pictorial scale, the results being analysed non-parametrically. The proportion (%) of ratings higher than or equal to/higher than the overall median of the samples was used as a rigorous estimate of product quality. These values were used to determine the colour and flavour changes in heated soymilk and their temperature dependence. The Z-values derived from the parametric and non-parametric analyses were in close agreement, ranging from 31 to 33 °C and from 30 to 32 °C for colour and flavour respectively. © 2000 Society of Chemical Industry