Squalene in grapefruit wax as a possible natural protectant against chilling injury

The influence of temperature conditioning on stored grapefruit against chilling injury (CI) as related to the fruit's neutral lipids in the peel was investigated. Squalene, a highly unsaturated C30 isoprene hydrocarbon, was found to be present in the epicuticular wax of grapefruit. The optimal temperature for biosynthesis of squalene in grapefruit was 15°C; this is also the temperature reported previously as the optimum temperature for conditioning grapefruit against chilling injury. Control and temperature-conditioned grapefruit were stored monthly over three seasons from 1986 to 1989. Fruits were rated for chilling injury and the levels of squalene were determined. An inverse relationship found between CI and squalene level suggested that squalene may protect grapefruit from CI.