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During the last decade there has been a continuous rise in consumption of fresh easy-to-peel mandarins. However, mandarins are much more perishable than other citrus fruit, mainly due to rapid deterioration in sensory acceptability after harvest. In the current review we discuss the biochemical components involved in forming the unique flavor of mandarins, and how postharvest storage operations influence taste and aroma and consequently consumer sensory acceptability. What we perceive as mandarin flavor is actually the combination of basic taste, aroma and mouth-feel. The taste of mandarins is principally governed by the levels of sugars and acids in the juice sacs and the relative ratios among them, whereas the aroma of mandarins is derived from a mixture of different aroma volatiles, including alcohols, aldehydes, ketones, terpenes/hydrocarbons and esters. During postharvest storage and marketing there is a gradual decrease in mandarin sensory acceptability, which has been attributed to decreases in acidity and typical mandarin flavor, paralleling an accumulation of off-flavor. Biochemical analysis of volatile and non-volatile constituents in mandarin juice demonstrated that these changes in sensory acceptability were concomitant with decreases in acidity and content of terpenes and aldehydes, which provide green, piney and citrus aroma on the one hand, and increases in ethanol fermentation metabolism products and esters on the other, which are likely to cause 'overripe' and off-flavors. Overall, we demonstrate the vast importance of the genetic background, maturity stage at harvest, commercial postharvest operation treatments, including curing, degreening and waxing, and storage duration on mandarin sensory quality.

We have modified the flavor and aroma of tomatoes by expressing the Ocimum basilicum geraniol synthase gene under the control of the tomato ripening-specific polygalacturonase promoter. A majority of untrained taste panelists preferred the transgenic fruits over controls. Monoterpene accumulation was at the expense of reduced lycopene accumulation. Similar approaches may be applicable for carotenoid-accumulating fruits and flowers of other species.

Postharvest decay caused by fungal pathogens is one of the most important factors causing economic losses for the worldwide industry of fresh horticultural produce. Despite the positive results of the use of conventional chemical fungicides, alternatives for decay control are needed because of increasing concerns related to their widespread and continued use. Low-toxicity chemical alternatives evaluated for control of postharvest diseases of temperate, subtropical and tropical fruit, and fruit-like vegetables are reviewed. These compounds should have acceptable antifungal activity with known and very low toxicological effects on mammals and minimal impact on the environment. In addition, they should be exempt from residue tolerances on agricultural commodities. Authorities confirm these characteristics by approving them as food additives or preservatives or as generally regarded as safe (GRAS) substances. Among these, the most important are inorganic or organic salts, e.g. carbonates, sorbates, benzoates, paraben salts, etc., and composite edible coatings formulated with antifungal ingredients. Hydrocolloids (polysaccharides such as cellulose derivatives, alginates, pectins, or gums, and various plant proteins) and food-grade lipids are the main components of the matrix of composite coatings. Interesting antifungal ingredients for edible coatings include GRAS salts, essential oils, and antagonistic microorganisms. Low-toxicity chemicals of natural origin include plant extracts and essential oils, antifungal peptides and small proteins, and coatings based on chitosan or plant gels like those from Aloe spp. Efficacy and overall performance, advantages, disadvantages, limitations, and potential combinations of these alternatives in hurdle technologies for postharvest decay control are discussed.

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