Modelling of transpiration rate of grape tomatoes. Semi-empirical and analytical approach

摘要

Transpiration is a well known physiological process of water loss from fresh products, associated with visual and texture degradation and loss of market value. A loss of 3-5% of the initial mass may cause in fresh products loss of freshness and visual attractiveness. Grape tomato has been increasingly accepted by consumers as "snacking tomato" and as an ingredient in mixed salads of fresh-cut vegetables. An experimental procedure was developed to record the associated with transpiration, water loss in grape tomatoes (Solanum lycopersicum, Lobello F1), at temperatures 10, 15 and 20 degrees C and relative humidity 70, 80 and 92%. Water activity was calculated and correlated with the respective mass loss; its average value was found 0.988 +/- 0.01. The mean transpiration rates ranged between 0.012 and 0.058 mg cm(-2) h(-2) for water vapour pressure deficit range of 0.061-0.662 kPa. A semi-empirical and an analytical model were developed to correlate the mass loss of grape tomatoes with the storage conditions (temperature and relative humidity) and storage. time. Both provided satisfactory fit to the experimental data. Finally, the air-film mass transfer coefficient (k(a)) and skin mass transfer coefficient (k(S)) were calculated and the k(S) coefficient correlated efficiently with an exponential equation with the respective water vapour pressure deficit