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Statistical Modeling of Tomato Firmness Evolution During Postharvest Storage

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

Citation:  Paper number  036136,  2003 ASAE Annual Meeting . (doi: 10.13031/2013.13916) @2003
Authors:   Bart De Ketelaere, Jeroen Lammertyn, Geert Molenberghs, Bart Nicolai, Josse De Baerdemaeker
Keywords:   Tomato firmness evolution, statistical modeling, mixed models, biological variability

In the quality assessment of horticultural products, a shift from destructive towards nondestructive quality sensors can be observed. These nondestructive sensors offer the appealing possibility to monitor quality changes of individual products over time, which was not possible before. Inherent to this shift, also an important change in experimental setting occurs since not all measurements are independent of each other. For instance, tomatoes with a low firmness today are likely to have a low firmness tomorrow, too. Together with the knowledge that biological material in general possesses a large variability, this type of repeated measures data necessitates a proper statistical analysis, and standard techniques used throughout literature in case of destructive sensors are not applicable anymore. Therefore, this contribution aims at introducing the concept of mixed models in the field of postharvest technology. The possibility of fitting mixed models in commercial software is rather recent (second half of the 90s) but has proven extremely useful in a broad range of application fields. In a practical experiment where the firmness of 13 different cultivars of tomatoes are monitored during postharvest storage with a commercial nondestructive firmness sensor for two harvests, it will be shown that the mixed model concept allows quantifying intratomato variability, inter-tomato variability and inter-cultivar variability, not only at a certain time point, but even as a function of storage time. The quantification of these different sources of variability is of great importance to researchers and growers, but was up to now never accounted for.

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