A respiration-diffusion model for 'Conference' pears II.: Simulations and relation to core breakdown

A respiration-diffusion model for 'Conference' pears was used to simulate three-dimensional internal 0, and CO, concentration profiles for intact pears as a function of the storage conditions. Although the skin was the major barrier to gas transport. the internal gas gradients in the fruit could not be neglected. Especially at high temperatures, when the respiration rate is high, the internal gradients increased considerably. A sensitivity analysis was carried out to assess the effect of bioloaical variability present on the respiration and diffusion parameters, and on the gas concentration profiles. It was found that at room temperature, the O-2 concentration underneath the fruit skin is mainly determined by the O-2 transfer coefficient and consumption rate. However, for typical storage temperatures this dependency is less pronounced. A comparison of simulated gas concentration contours of pears stored with delayed controlled atmosphere and those immediately stored under controlled atmosphere (CA), illustrated the importance of an appropriate storage management right after harvest. When CA storage was applied immediately after harvest, the O-2 and CO2 concentrations reached very low and very high values, respectively, possibly causing irreversible membrane damage and inducing core breakdown. These values were not found for delayed controlled atmosphere. A model validation experiment on affected pears indicated that the diffusion and respiration parameters for affected tissue were different from those for healthy tissue. (C) 2003 Elsevier B.V. All rights reserved.