Postharvest is a critical process in preserving the quality and shelf life of the fruit. One of the most important variables affecting the quality of the cherry in postharvest is temperature, which influences not only the dehydration of the fruit but also the respiratory rate and the production of ethylene, two processes that determine the speed of ripening and deterioration of the fruit due to the loss of its commercial value.
Together with INIA's Postharvest Laboratory, we studied the respiratory rate of three cherry varieties at different temperatures from 0°C to 30°C. The results presented below show a similar evolution in the three varieties, and show how the respiratory rate increases as the temperature increases. The findings of this study contribute to the understanding of cherry physiology in postharvest, which can help improve management and conservation practices in the supply chain of this export fruit.
Samples of freshly harvested Santina, Lapins and Regina cherries were evaluated, which were subjected to different treatments corresponding to different temperatures: 0°C, 5°C, 10°C, 20°C, 25°C and 30°C. For this, the samples were exposed to an environment with the target temperature and, once the temperature was stabilized, the carbon dioxide (CO) production rate was determined.2) under each condition.
Figure 1 shows the CO production rate2 at the different temperatures studied in cherries var. Santina, Lapins and Regina. As can be observed, the production of CO2 It increases as the temperature increases, from values close to 0 when the temperature is 0°C to reaching values between 40 and 65 µL CO2 / kg h when the fruit temperature is 30°C. This increase is minimal when going from 0°C to 5°C and moderate between 5°C and 20°C. However, it is from this last temperature that the respiration rate of cherries undergoes a substantial increase that doubles its value when going from 20°C to 25°C.
Knowing these values is very important, particularly in relation to what is observed at high temperatures, which are those that are usually observed in the fields during the harvest period. This graph, which shows the great difference that exists in the cherry's respiratory rate between 20°C and 30°C, shows the importance of controlling the pulp temperature during the harvest and the need to implement management measures that maintain it at values close to 20°C, such as the use of humidifiers within the fruit collection centers in the field.
Figure 1. CO production rate2 in cherries var. Santina, Lapins and Regina at different temperatures.
Figure 2 shows the effect of using a good humidification system in the collection centers on the pulp temperature of the cherries stored inside. This graph corresponds to the results of a test in which we monitored the pulp temperature of freshly harvested cherries entering a collection center. In this study, fruit samples were taken at 20°C and 30°C, which were stored in a conventional collection center (without humidification) and in a collection center with our humidification systems. The results show that, while in a conventional collection centre the temperature of cherry pulp at 20°C rises to 25°C and cherries at 30°C maintain their temperature between 25 and 30°C, the collection centre with humidification manages to reduce the temperature of the cherry pulp incoming at 30°C to 20°C and maintains the temperature of those cherries that arrived at an initial temperature of 20°C.
As reviewed in figure 1 with respect to the CO production rate2 cherries at 20°C, 25°C and 30°C, we can conclude that a humidified collection center will keep the respiratory rate under control, preventing it from doubling (which occurs when temperatures reach 25°C or more).
Figure 2. Evolution of pulp temperature inside a conventional collection center without humidification (red) and a humidified collection center (blue) of cherries with an initial pulp temperature of 20°C (dotted line) and 30°C (solid line).
What is the respiratory rate? of cherries when comparing with others export fruits?
The same study was also carried out on different varieties of blueberries and table grapes (Figures 3 and 4, respectively). The values observed for different varieties of blueberries were higher than those observed for cherries, while the values observed for six different varieties of table grapes were lower.
Figure 3. CO production rate2 in blueberries var. Suzie blue, Duke, Blue ribbon, Legacy and Top shelf at different temperatures.
Figure 4. CO production rate2 in table grape var. Thompson seedless, Arra 15, Sweet celebration, Pristine, Timco and Red globe.
