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The objective of the present study was to compare two chemometric approaches for characterizing the rheological properties of fruits from puncture test force/displacement curves. The first approach (parameter approach) computed six texture parameters from the curves, which were supposed to be representative of skin hardness, fruit deformation before skin rupture, flesh firmness and mechanical work needed to penetrate the fruit. The second approach (whole curve approach) used the whole digitized curve (300 data points) in further data processing. Two experimental studies were compared: first, the variability of the rheological parameters of five apple cultivars; second, the rheological variability that was characterized as a function of storage conditions. For both approaches, factorial discriminant analysis was applied to discriminate the fruits based on the measured rheological properties. The qualitative groups in factorial discriminant analysis were either the apple cultivar or the storage conditions (days and temperatures of storage). The tests were carried out using cross-validation procedures, making it possible to compute the number of fruits correctly identified. Thus the percentage of correct identification was 92% and 87% for using the parameter and the whole curve approaches, respectively. The discrimination of storage duration was less accurate for both approaches giving about 50% correct identifications. Comparison of the percentage of correct classifications based on the whole curve 3 Corresponding author.Journal of Texture Studies 36 (2005) 387-401. All Rights Reserved. © Copyright 2005, Blackwell Publishing 387 and the parameter approaches showed that the six computed parameters gave a good summary of the information present in the curve. The whole curve approach showed that some additional information, not present in the six parameters, may be appropriate for a complete description of the fruit rheology. KEYWORDSApple, digitized curve, factorial discriminant analysis, penetrometry, puncture test, storage, texture 388 C. CAMPS ET AL. COMPARISON OF TWO CHEMOMETRIC APPROACHES

Improved non-destructive instrumental approaches for grading fruit during post-harvest could be an efficient way to monitor stock in the apple industry. The objective of this study was to evaluate the ability of visible-near infrared (vis-NIR) spectroscopy in reflectance mode for classifying apples left on the shelf or stored in a cooled room. The ability of NIR spectroscopy to classify the duration of storage of three apple cultivars in two storage modalities was evaluated. A total of 450 fruit, sampled after 7, 14, 28, 60, 90 and 120 days of storage in a cooled room (CR) and 7, 14 and 28 days in shelflife (SL), has been studied. The classification of these modalities was analysed by factorial discriminant analysis (FDA) pooling the spectral data of all cultivars (global models) into a common data set. Then, the cultivar effect on the classification of the same modalities was analysed by processing data from each cultivar in separate factorial descriminant analyses. A preliminary analysis showed the genetic variability of spectral data due to the three apple cultivars. We show that vis-NIR spectroscopy allowed the correct classification of the fruits of each cultivar by more than 95%. The classification relied on both vis and NIR absorption bands: 500, 680, 1400 to 1700, 1850, 1950, 2200 and 2300 nm. We show that storage modalities of global models can be classified by more than 75% and 83% for fruits stored in a cooled room and shelf, respectively. Classification of the same storage modalities was improved by cultivar models with percentage of individuals correctly classified of 86% (Gala), 89% (Elstar) and 85% (Smoothee) for fruits stored in a cooled room and 95% (Gala), 98% (Elstar) and 95% (Smoothee) for fruits left in shelflife. We conclude that despite the slight increase of efficiency of the models when we considered each apple cultivar separately, global models applicable to a set of different cultivars presents a correct level of classification and could be usefull for some commercial applications.

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