Physiology of Lightly Processed Fruits and Vegetables

Fig. 1. Wound ethylene production at 20C by tomato pericarp disks cut from the blossom, equator, and stem regions of mature green fruit. Data are means The physiology of lightly processed (LP) fruits and vegetables is essentially the physiology of wounded tissue. This type of processing, involving abrasion, peeling, slicing, chopping, or shredding, differs from traditional processing in that the tissue remains viable (or “fresh”) during subsequent handling. Thus, the behavior of the tissue is generally typical of that observed in plant tissues that have been wounded or exposed to stress conditions. This behavior includes increased respiration and ethylene production, and, in some cases, induction of wound-healing processes. Other consequences of wounding are chemical or physical in nature, such as oxidative browning reactions and lipid oxidation, or enhanced water loss. Appearance of new RNA and protein species in wounded tissue provides evidence for genomic control of the response. Many factors may affect the intensity of the wound response in LP tissues. Among these are species and variety, stage of physiological maturity, extent of wounding, temperature, O2 and CO2 concentrations, water vapor pressure, and various inhibitors. Wounded tissues undergo accelerated deterioration and senescence. Minimizing the negative consequences of wounding in LP fruits and vegetables will result in increased shelf life and greater maintenance of nutritional, appearance, and flavor quality in these products. Reviews of physiological aspects of lightly processed products (LPP) that have appeared in recent years include Huxsoll et al. (1989), King and Bolin (1989), Rolle and Chism (1987), and Watada et al. (1990). Miller’s (1992) review of the postharvest physiology of mechanical stress in fruits and vegetables is germane to this discussion, as are Shewfelt’s (1987) review of quality aspects and Klein’s (1987) review of nutritional consequences of lightly processing fruits and vegetables.