Postharvest precooling of fruit and vegetables: A review

Background: Precooling is a critical step in the postharvest cold chain. Studies of the precooling of fruit and vegetables are based on the strong interactions between modelling, engineering, physiology and commercial outcomes. In recent years, new progress in precooling has been achieved. These achievements include different cooling strategies, research into precooling mechanisms, and numerical simulations. This review aims to provide the most recent information about precooling and promote its application in the fruit and vegetable industry. Scope and approach: Different precooling strategies are evaluated with respect to the cooling rate, cooling uniformity, and multiscale simulation. An overview of mathematical modeling approaches used to quantitatively describe precooling processes for computer-aided designs is provided. The effect of precooling on fruit quality at the physiological and molecular levels is outlined. Key findings and conclusions: Numerical simulations have become widely used to improve the precooling performance. Cooling homogeneity, in particular, has attracted increasing attention in recent studies because of the substantial effects of cooling homogeneity on the precooling efficiency and produce quality. The spatial scale of numerical simulations of the precooling process has started to become more precise and specific. Recent numerical simulations have focused on the bin and package scale. Models of transport processes at multiple spatial scales are investigated using multiscale modeling. Moreover, the effect of precooling on produce quality has recently received increasing attention. In addition, the investigation of the effect of precooling on fruit at the metabolomic and genomic levels has become an emerging trend and has provided deeper insights into the molecular mechanisms underlying the effect of precooling treatments on fruit.