Determinação da umidade relativa do ar em câmaras frigoríficas e sua relação com a qualidade de maçãs

Abstract

Given the difficulties of determining the relative humidity (RH) in rooms used for the storage of apples accurately, the aim of this study was to calibrate the ventilated evaporimeter, an instrument used to measure the water evaporation that occurs due to the relative humidity and temperature, as well as evaluating if the mass loss improves gas diffusion and contributes to the quality maintenance of Royal Gala and Galaxy apples during storage and enables the use of a high CO2 partial pressure. This work also aimed to evaluate if there are any differences in the levels of mass loss between apples that were placed in distinct positions in the controlled atmosphere storage room. In order to do this, four experiments were performed: the first aimed to calibrate the ventilated evaporimeter in 85, 90, 95 and 100% of RH at a temperature of 1ºC. In the second experiment, the treatments were consisted by the period and level of mass loss (1 or 3%) in Royal Gala apple stored in controlled atmosphere at a temperature of 1ºC. For the third experiment, carried out with Galaxy apple, treatments were conducted with a high CO2 (3.0 kPa) and a low O2 (0.4 kPa) partial pressure associated with 3% of mass loss, aside from two treatments with a respiratory quotient (RQ) of 1.5, at 1ºC. For the fourth experiment, apple samples were placed in different positions in a commercial apple storage room in order to evaluate the mass loss. It was possible to obtain an average value of evaporation, in cm day-1, at a temperature of 1ºC, in different relative humidities through the calibration of the evaporimeter and the daily determination of water evaporation. The mass loss, both initial and linear, during the storage period, improved gas diffusion in the pulp of Royal Gala apple and reduced cracking, flesh breakdown and mealiness. The mass loss in Galaxy apple also improved the gas diffusion, which enabled the use of 3.0 kPa of CO2, however, with an RQ 1.5, a high CO2 partial pressure cannot be used. Mass loss occurred heterogeneously in the commercial storage room, being higher at the bottom and on the front of the storage room.