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Mixed Models to Describe Quality Evolution During Storage and Shelf Life of Biological Products

Published by the American Society of Agricultural and Biological Engineers, St. Joseph, Michigan

Citation:  Paper number  036210,  2003 ASAE Annual Meeting . (doi: 10.13031/2013.15339)
Authors:   Jeroen Lammertyn, Bart De Ketelaere, David Marquenie, Geert Molenberghs, Bart Nicolaï
Keywords:   Biological variability, mixed models, quality, repeated measures, UV-C treatment

This paper addresses the application of generalised linear mixed models for multicategorical responses to model the quality evolution of of biological products during storage. It is illustrated that this technique works well to analyse repeated categorical quality measures over time on the same subject. The inclusion of random intercepts and slopes, allowed to describe the biological variability that is inherently present in batches of fruits. The linear mixed models for continuous response were adapted for multicategorical response according to the threshold concept described in the literature. The benefits of this statistical technique are illustrated by means of a typical data structure encountered in postharvest research. The effect of UV-C treatment on the sepal quality of strawberries was followed and modelled during storage. It was found that UV-C treatment retards the quality decay of the sepals for doses up to 0.1 J/cm2, but when higher doses were applied the treatment became destructive and the sepals dehydrated and discoloured brown. Since the fungal growth on the strawberry fruit flesh is slowed down significantly starting from a dose of 0.05 J/cm2, an optimal dose of 0.1 J/cm2 is recommended to improve the quality retention of the strawberry including the visual aspect of the sepals.

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