| Popis: |
The trend for tropical fresh-cut fruits is expanding, particularly in food retail segments. Fruits are usually washed, peeled, sliced, chopped and packaged prior to retail distribution. Postharvest discoloration is often an aggravating concern in this minimally processed sector, as the browning of harvested fruits decreases their cosmetic and economic values. In tropical fruits such as mango, pineapple, longan, and lychee, browning is physiologically associated to fruit desiccation, to chilling injury, and to the natural oxidative degradation of fruit pigments. Biochemical pathways involve the enzymes polyphenol oxidase (PPO) and polyphenol peroxidase (POD), which catalyze the oxidation of free radicals, phenolic compounds, and other antioxidants. Under conditions such as suboptimal temperatures storage, high humidity, plant disease, and natural fruit senescence, plant cells generate free radicals that attack the lipoprotein membranes, resulting in a loss of intracellular compartmentation, ultimately releasing secluded phenols. The brown pigmentation thus results from the enzymatic reactions of either PPO or POD with phenols or from the nonenzymatic process of polyphenol autoxidation. These tropical plants, however, possess antioxidative mechanisms that remove free radicals and potentially inhibit or delay the browning process. Understanding these mechanisms in fresh-cut produce has led to the development of techniques that ideally could control browning discoloration during storage and shop display. Within this chapter, we provide a detailed overview of the enzymatic browning processes and current antibrowning approaches in fresh-cut tropical fruit produce. |
