ISHS Acta Horticulturae 93: Symposium on Quality of Vegetables
TOMATO QUALITY: POTENTIAL FOR DEVELOPING CULTIVARS WITH IMPROVED FLAVOR |
| Author: | M. Allen Stevens |
| Abstract:
Picking tomato fruits before they are table-ripe alter their flavor characteristics. The most important resulting variant flavor characteristics are a decreased sweetness and a pronounced off-flavor. In 'Cal Ace', the reduced sweetness was found to be due largely to reduced sugar content, and the off-flavor to increased concentrations of 2-methyl-2-butenal. Other volatiles appear to contribute to the off-flavor in other cultivars that varied greatly in intensity of off-flavor. Use of mutants with inhibited ripening are one method of developing cultivars that can be picked at later stages, but present genotypes containing these genes have poor color and lack firmness. Some breeders are using genes that increase lycopene content to improve color. Increases in lycopene, however, may change the concentrations of certain volatile compounds and alter flavor. The extreme firmness of certain processing cultivars may be useful for developing cultivars that can be picked at later stages of ripeness. This firmness, a result of greater cell wall levels, results in fruits that can be stored for relatively long periods after they are fully ripe. Certain of the tomato cultivars tested differed greatly in flavor. Sweetness was determined largely by the content of reducing sugars, while sourness was related to titratable acidity and pH. Overall flavor intensity was determined largely by sugar and acid contents. Newly synthesized F1 hybrids with high levels of sugar and acid had much greater sweetness, sourness, tomatolike character, and overall flavor intensity than the standard cultivar 'Cal Ace.' An important goal of plant breeders interested in flavor should be higher sugar and acid contents and, possibly, greater firmness. Increased solids content will be a difficult problem, particularly in high-yielding cultivars with a concentrated fruit set. The genetic potential for increasing acid content appears to be good since there are genotypes with high acid concentration under simple genetic control, but there will then be a problem of competition for limited photosynthate. Genotypes differ in the concentrations of important buffers, and decreased phosphorus content results in lower pH levels. Genotypes also differ greatly in the concentrations of certain volatile compounds. Volatiles have been shown to be important in flavor differences in some cases, whereas in many cases it has not been possible to demonstrate a relationship. One of the striking effects of volatiles is the off-flavor defect in fruits picked before they are ripe. | |
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