To develop a regression model for the prediction of the physical properties, applicable to peach fruits stored at different temperatures, the respiration rate (CO2 output rate) and five physical parameters of peach fruits (cv. Kanoiwa-Hakutou) were investigated in the context of storage at 0, 5, 10, 15, 25, and 35℃. The firmness index of the peach fruits was measured using a hand-held firmness tester, whereas the maximum load, spring constant at small and large deformations, and flesh firmness were measured using a universal firmness tester. The changes in the five physical parameters over time showed similar tendencies, and the physical parameters correlated well with cumulative respiration. Consequently, we developed a mathematical model for the prediction of the physical parameters of individual samples based on their cumulative respiration, which followed a sigmoid-type function. The data obtained for these five physical parameters using the model showed a high correlation coefficient (R2＝0.819－0.921), and the spring constant at a small deformation showed the highest value among all parameters. These results indicate that developing a model using cumulative respiration as a variable is feasible and allows the prediction of changes in the firmness characteristics of peach fruits during the postharvest period.
