Thermal insulation of the winter cauliflower curd by wrapper‐leaves

Abstract

SUMMARYThe role of leaves as insulation for mature curds during exposure to frost has been investigated for winter‐harvested cauliflower. The inner, wrapper‐leaves and their enclosed air spaces provided significant protection for the curd tissues in mild frost, but under more severe conditions (below – 2.5°C) were ineffective. A relationship between higher wrapper‐leaf number and increased insulation was described. The increase in insulation however, was small even with much higher wrapper‐leaf numbers. Exposure of the curd surface at maturity was found to prevent the insulating effect of wrapper‐leaves, particularly if the diameter of the exposed area was greater than 6 cm. The data also suggested a possible role for the exposed stem of the cauliflower as a site of heat loss that may adversely affect curd temperature.It is postulated that breeding for improved frost resistance by greatly increasing wrapper‐leaf number would not be effective, although any reduction in wrapper‐leaf number and the presence of tightly wrapped curds should be avoided. Furthermore, exposure of the curd surface at maturity should be kept to a minimum.