Modeling the effects of high humidity and airflow on transpiration of fresh produce.

摘要

Scope and method of study. The ability to minimize product weight loss during storage is important in the fresh produce industry. One of the most important tools to predict storage weight loss of high-moisture, respiring products is mathematical models. A computer model was constructed using existing models to better predict weight loss from fresh produce at high relative humidity. Many product thermal-physical properties used as inputs to models are poorly defined due to the variability among commodities and cultivars. These ill-defined product thermal-physical properties that significantly affect weight loss were identified and quantified at different storage conditions. Sensitivity analysis was done at 5 and 25{dollar}{bsol}sp{bsol}circ{dollar}C, 50-100% RH, and 0.005-5.0 m/s air velocity conditions allowing skin mass transfer coefficient (k{dollar}{bsol}rm{bsol}sb{lcub}s{rcub}){dollar} and vapor-pressure lowering effect of dissolved solutes (VPL) to vary from 5 to {dollar}25{bsol}times10{bsol}sp{lcub}-6{rcub}{dollar} and 0.98 to 0.995, respectively. Peach weight loss was measured at 2 to 3 day intervals for 20 days in storage to determine the effects of temperature, airflow, and relative humidity compared to model predictions.; Findings and conclusions. Three parameters were identified having considerable influence on predicted weight loss: {dollar}{bsol}rm k{bsol}sb{lcub}s{rcub},{dollar} VPL, and radius. Weight loss predictions due to ranges in {dollar}{bsol}rm k{bsol}sb{lcub}s{rcub}{dollar} were non-linear at low air velocity and linear at high air velocity. Responses to ranges in VPL were linear and more pronounced at high relative humidity. Effect of k{dollar}{bsol}rm{bsol}sb{lcub}s{rcub}{dollar} on predicted weight loss decreased with higher relative humidity and temperature and increased with higher air velocity. VPL alone and combined with k{dollar}{bsol}rm{bsol}sb{lcub}s{rcub}{dollar} affected predicted weight loss most at lower temperature, and higher velocity and relative humidity. The developed model better predicted weight loss at high relative humidity ({dollar}{bsol}geq{dollar}95%) than the published model. The rate of measured peach weight loss was constant with storage time. Measured weight loss was indirectly proportional to relative humidity and directly proportional to airflow. Model-predicted weight loss compared best to measured weight loss for high air velocity conditions. Choice of {dollar}{bsol}rm k{bsol}sb{lcub}s{rcub}{dollar} and VPL, as model input parameters, was shown to have considerable influence on the predicted weight loss.