KEEPING QUALITY OF CUCUMBER FRUITS PREDICTED BY BIOLOGICAL AGE

In the absence of defects, colour is one of the few practical criteria for assessing cucumber (Cucumis sativus L.) quality. However, cucumbe rs with the same colour at harvest can exhibit large differences in qu ality upon reaching the consumer. Photochemical yield (Phi(PSII)), pho tochemical quenching (q(p)) and a photosystem I evaluation (k(e)), as internal quality measurements, were used in combination with an extern al quality measurement, represented by the colour, to test if the keep ing quality could be predicted on the basis of these measurements. Kee ping quality is defined as the time for a cucumber to reach a certain predefined colour limit. To test the hypothesis, colour changes for 20 00 cucumbers were measured during storage at 20 degrees C and 100% RH. The colour data were fitted to a model where a correction for biologi cal age (C-ba) was applied to each individual cucumber. The correction for biological age could be linked to the measured Phi(PSII), q(p) an d k(e) values. Statistical analyses resulted in values for the maximum (green) and minimum colour (yellow) for each cucumber. The minimum co lour could be correlated with different cultivars and the maximum colo ur with plant growing conditions. After a suitable transformation by a neural network, C-ba could be estimated based on the values of Phi(PS II), q(p) and k(e) and the initial colour. Predictions on the keeping quality by the model resulted in an explained variance of 74% (R-adj(2 ) = 0.74). (C) 1997 Elsevier Science B.V.