THE EFFECT OF VACUUM PRECOOLING ON THE HALF COOLING PERIOD AND QUALITY CHARACTERISTIC OF ICEBERG LETTUCE

The most important factor which affects the postharvest life and quality of horticultural crops is temperature.
Quality loss after harvest occurs as a result of physiological and biological processes caused by respiration and other activities (Anon., 1990). Therefore, it is necessary to not only cool the product, but cool it quickly after harvest (Turk and Bolukoglu, 1991). Putting the products into cold storage before precooling causes significant water loss because of the vapor pressure difference (VPD) caused by temperature difference.
However, it is difficult to lower the core temperature of leafy vegetables, especially those in which the leaves overlap each other and which have a high surface/volume ratio; such as head lettuce (Anon., 1990; Thompson and Rumsey, 1984) because the static air between the overlapping leaves acts as a very good insulation material.
Such leafy vegetables are best precooled by vacuum (Anon., 1990; Pasqualone, 1986; Savas et al., 1992).

Physiological Basis of Postharvest Technologies

R. Turk, E. Celik

https://doi.org/10.17660/ActaHortic.1993.343.77