ABSTRACT
The main effect of the low temperature application during postharvest storage is a reduction of the fruit metabolism and consequently a delay of the evolution of the parameters related to fruit ripening and quality loss (Chapter 3). One of the main parameters determining the metabolic activity of a fruit is its respiration rate, which is usually associated with the commodity deterioration. Respiration rate of a produce is dependent on a wide range of variables, of which temperature is considered the most important in modulating this physiological parameter. As can be seen in Figure 4.1, the respiration rate of apple, orange, lemon, and banana increased as the assay temperature was enhanced, although differences exist among fruit types. Thus, at 30°C oranges showed a respiration rate of ≈40 mg kg-1 h-1 while banana showed ≈170 mg kg-1 h-1. Moreover, differences were also found in the temperature at which the maximum respiration rate was achieved, this temperature being 50°C for apple and orange, 45°C for lemon, and 40°C for banana. The diminution of the temperature led to a reduction in the respiration rate for all fruits, and calculated Q10, that is, the reduction of the reactions between two
temperatures that differ in 10°C, was 1.63 for apple and 1.9 for the other fruits. Interestingly, at the lowest temperature (1°C) there were still differences among fruits and respiration rates followed the same sequence, with banana having the highest and orange the lowest (≈40 and 5 mg kg-1 h-1, respectively).
