The formation of ice in detached kiwifruit (Actinidia deliciosa) fruit was investigated in a freeze chamber by thermal analysis. Ice nucleation (IN) occurred between -3.1 and -4.9-degrees-C. The distribution of IN temperatures followed a normal distribution with a mean (+/- SD) at -3.9 +/- 0.5-degrees-C. Forth-three cases were also monitored in the field, where a sample of fruit was checked for frost damage whenever the air temperature dropped below zero. The field data obtained confirmed that exposure of fruits to air temperatures below -3-degrees-C creates the conditions for a freezing event in kiwifruit fruit. The longer the exposure of fruits to temperatures below -3-degrees-C and/or the lower the temperature, the higher the probability of ice nucleation. The relationship between air temperature and the temperature of fruits under field conditions is discussed for two different hoar frost cases: advective frost and radiation frost.
