Colour Evolution of Rosé Wines after Bottling

Abstract

This research reports on the colour evolution of six rosé wines during sixteen months of storage in the bottle.
Colour changes were determined in terms of CIELAB colour parameters and in terms of the common colour
categories used in visual assessment. The colour measurement method reproduces the visual assessment
conditions during wine tasting with respect to wine sampler, illuminating source, observing background and
sample-observer geometry. CIELAB L*, a*, b*, C* and hab colour coordinates were determined at seven different
times (t = 0, 20, 80, 153, 217, 300 and 473 days). The time evolution of colour coordinate values was studied using
models related to linear, quadratic and exponential rise to a maximum. Adjusted R2, average standard error and
CIELAB ΔE* colour difference were used to compare models and evaluate their performance. For each colour
coordinate, the accuracy of model predictions was similar to the standard deviation associated with a single
measurement. An average ΔE* = 0.92 with a 90 percentile value ΔE*90% = 1.50 was obtained between measured
and predicted colour. These values are smaller than human colour discrimination thresholds. The classification
into colour categories at different times depends on the wine sample. It was found that all wines take three to
four months to change from raspberry to strawberry colour and seven to eight months to reach the redcurrant
category. Only two wines had developed salmon colour by the end of the experiment.