Flavour volatile production and regulation in fruit

Consumption of fresh fruits is increasing as consumers become more aware of their nutritional value and role in disease prevention. Improving the flavour properties of fresh fruit reaching the consumer would add value, increase consumption, and create new markets for these commodities. One of the important characteristics of fruit ripening is volatile aroma production. Using apples (Malus domestica), strawberries (Fragaria ananassa Duch.) and melons (Cucumis melo L. var. reticulatus Naud; C. melo L. inodorus; C. melo L. cantalupensis) fruit as examples, this review focuses on recent developments in fruit aroma research. Both sensory studies and instrumental analysis confirm the importance of volatile production in fruit and its contribution to eating quality. Sensory analysis should further define the contribution of individual volatile compounds to total flavour quality. Volatile biosynthesis and its contribution to fruit eating quality is very complex, and is influenced by many factors, such as genome, harvest maturity, and postharvest handling and storage. Application of 1-methylcyclopropene (1-MCP) and transgenic lines suppressing ethylene action and biosynthesis demonstrate ethylene involvement in volatile formation and provide useful research tools to elucidate the volatile production process during fruit ripening. Cloning of genes and characterization of enzymes responsible for volatile production helps us to understand the biochemical pathways and control mechanisms. Despite the exciting developments in flavour research, several challenges still remain to be solved. An understanding of the fundamental mechanisms controlling changes in flavour quality is limited, and most biochemical pathways determining this quality trait are still unknown. As part of secondary metabolism, volatile production in fruit is a complex process with tightly controlled systems involving substrates, enzymes and energy from many pathways. It is our hope that the biochemical pathways regulating the synthesis of volatile compounds in fruit will be determined using integrated approaches, including biochemical, genomic, proteomic and microscopy tools to determine fundamental metabolism and its localization. Combining these efforts with direct measurement of sensory properties will lead us to new methods to optimize and retain fruit flavour in the market place.