SIMULATION OF THE EFFECT OF HEATING ON DISINFESTATION PROTOCOLS FOR PAPAYA

Abstract

The disinfestation protocol for fruit often requires a delicate balance between suppression of the pest and avoidance of fruit damage. In Hawaii both hot-water and hot-air treatments are used for papaya destined for export. A computer simulation of the heat flow can be used to obtain the temperature Tα(x,t) at every point x in the papaya and every time t for any given heating protocol α. The activity of the ethylene forming enzyme (EFE) has been used as a measure of fruit damage and the “kill” of fruit-fly larvae/eggs as a measure of pest control. The degradation of the EFE measured experimentally for a fixed temperature T and at several times t can be analyzed to yield a rate expression R1(T,t). Similarly the survival of fruit-fly larvae/eggs can be used to establish a rate expression R2(T,t). The temperature space-time expression, Tα(x,t), for a chosen heating protocol α, and the rate laws R1(T,t) and R2(T,t) can be used to calculate the effect on EFE activity, EFEα(x,t), and pest control, PCα(x,t), at every point in the fruit and time of the protocol. For example the effect of different heating schedules, different heating fluids or even the role of “pre-conditioning” can be assessed.