Precooling of table grapes on a commercial scale as function of packaging

Abstract

Although precooling by forced air is widely used to remove field heat from fresh table grapes, there is no knowledge about its use and efficiency. Factors influencing the process include temperature and relative air humidity, amount and initial temperature of the fruits, air velocity, and packaging. The objective of this study was to evaluate the cooling effect and efficiency of forced air cooling on table grapes in two types of packages. The experimental method used randomized blocks, in a 2 × 3 factorials, corresponding to two package types (polystyrene and cardboard) and three heights on the pallet - lower, middle, and upper - with four replicates. The temperature gradient in the direction of the airflow was evaluated. There was heterogeneity in cooling, both vertically and horizontally, on the pallets with a central heat zone for both the directions. None of the packages was suitable for fast cooling as both types of packages showed a cooling time of 15.5 h; moreover, relative humidity values were far below the ideal value for table grapes.