The edible quality of peaches (Prunus persica L. Batsch) to a great extent depends on their sweetness, which is related to sugar composition. Our objective was to develop a model to predict carbon partitioning within fruit flesh and to predict the sucrose, sorbitol, glucose, and fructose contents. The model is dynamic and deterministic and was designed to be driven by the flesh dry-weight growth curve, flesh water content, and temperature data. It uses differential equations where the state of the system is defined by variables that describe how much carbon is present as each form of sugar and as other compounds (acids and structural carbohydrates). The rates of change of these amounts of carbon depend on the current values of corresponding variables and on the transfer functions between them. These functions are defined by rate constants or by functions of degree-days after full bloom. The model was calibrated and tested using data sets from treatments that covered several leaf: fruit ratios. The predictions of the model were in fairly good agreement with experimental data. A sensitivity analysis was performed to identify the most influential transfer function parameters. Carbon flows between sugar forms were analyzed. Sucrose, which was the most abundant sugar, and fructose, which is the sweetest, contributed most to fruit sweetness. Simulations were performed to study the effects of changes in fruit growth-curve parameters on sugar contents and concentrations.

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Gas transport and exchange through the perforations in micro-perforated packs used in modified atmosphere packaging were numerically modelled by using Stephan-Maxwell laws, and, outside these perforations, by Fick's law. The model accounts simultaneously for oxygen, carbon dioxide, nitrogen, argon and water vapour. Fruit and vegetable respiration was approximated by Michaelis-Menten kinetics depending on oxygen concentration with an uncompetitive inhibition due to carbon dioxide. Concentration equilibrium was reached after 2 to 3 days, depending on the void volume and on the diffusion properties of the packs. The equilibrium concentrations were dependent on the number of perforations, their diameter, the thickness of the film and the temperature. However, a pack which makes 10% oxygen possible within the pack at 10°C might induce anaerobiosis at 20°C.

The correlations among quality parameters of peach fruit (Prunus persica L Batsch) were studied for eight different cultivar-shape-site-nitrogenseason combinations ('treatments'). Between 66 and 183 fruits were taken from each treatment and the quality parameters of skin colour, flesh firmness and taste were measured. Differences and similarities between treatments were analysed using a recent development in biplot multivariate analysis: the ACT method (Analyse Conjointe de Tableaux), which allows the study of several data tables in one unique analysis. Each treatment was characterised by a data table where records were the fruit and variables were quality parameters. A common pattern of correlation between quality parameters was found for all the treatments. Two main independent gradients were described. The first was a colour gradient and the second was a taste gradient. In the latter, the concentrations of sucrose and malic acid varied inversely with citric acid concentration. The firmness and the concentration of reducing sugars were independent of these gradients.

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