Estimation of the Cooling Rate of Six Olive Cultivars Using Thermal Imaging

Abstract

Bringing the olive harvest period forward leads to storing fruit in field temperatures that risk jeopardizing its quality. Knowledge about the bio-thermal characteristics of olives is crucial when considering their cooling, although published research on the subject is limited. In this work, the cooling rate of the fruit of six olive cultivars has been empirically determined by measuring the evolution of their low temperature under controlled conditions by thermal imaging. Based on these data, the cooling time needed to cool the fruit to 22 °C was estimated, considering the biometric characteristics of the individual fruit, a field temperature from 26 to 42 °C, and a room cooling temperature from −8 to −20 °C. The results showed differences among the cultivars and the need to further investigate the specific heat requirements for small varieties and the impact of the conduction factor on the heavier ones. The simulation suggests that between 2 min (for the light Arbequina and Koroneiki cultivars) and 5 min (for the heavier Verdial and Gordal cultivars) suffice to cool the fruit to the desired temperature with a room temperature of −16 °C. These results show the feasibility of developing technological solutions for cooling olives before their industrial processing with industrial applications such as cooling tunnels on individual fruit.

Keywords

• harvesting
• storage
• biothermal characteristics
• refrigeration temperature
• half time