ISHS Acta Horticulturae 368: International Symposium on Postharvest Treatment of Horticultural Crops
PRODUCTION AND DEVELOPMENT OF VOLATILE AROMA COMPOUNDS OF APPLE FRUITS AT DIFFERENT TIMES OF MATURITY |
| Authors: | J. Song, F. Bangerth |
| Keywords: | apple, harvest date, aroma production, aroma- precursors, ethylene treatment, amino acids and fatty acids |
| Abstract:
The degree of maturity of an apple fruit is one of the most important factors in determining aroma production. Immaturely harvested fruits generally have a low production of aroma volatiles. Our investigations with the apple cv. "Golden Delicious" indicated that beside a lower ethylene production and reduced respiration, fruits harvested about 4 weeks before an estimated "optimum harvest time" were very low in their production of volatile compounds. This deficiency in aroma production was more and more overcome as fruits approached the optimal harvest date. When these fruits were treated with precursors of volatile substances (e.g. various aldehydes) the release of corresponding alcohols and esters was greatly stimulated. The enhanced aroma production, however, lasted only for a comparatively short time (72 hours). This, and the finding that the development of lipoxygenase activity during ripening did not coincide with aroma production, led to the conclusion that enzymes catalysing the later steps in aroma production are not a limiting factor in the biosynthesis of volatile aroma compounds of early harvested fruits. The analysis of fatty acids, early precursors of volatile aroma compounds, indicat that earlier harvested fruits contained much lower amounts of these constituents, particularly of palmitic-, stearic-, oleic-, and linoleic acids. Ethylene treatment of early harvested fruits stimulated fatty acids as well as aroma production. The production of "branched chain" aroma compounds was stimulated by ethylene treatment earlier than "straight chain" aroma compounds, indicating that ethylene treatment also affects the biosynthesis of branched amino acids. It is concluded that the low aroma production of early harvested apple fruits is due to a reduced capacity for the synthesis of fatty acids and particular amino acids of these fruits. | |
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