Date of Award:

5-1968

Document Type:

Dissertation

Degree Name:

Doctor of Philosophy (PhD)

Department:

Nutrition, Dietetics, and Food Sciences

Department name when degree awarded

Food Science and Technology

Committee Chair(s)

D. K. Salunkhe

Committee

D. K. Salunkhe

Committee

L. E. Olson

Committee

H. O. Van Orden

Committee

P. B. Larsen

Abstract

Investigations were carried out to isolate, identify, and to characterize, major volatile components of tomato fruit. Simultaneously, the confirmation was extended to the reported tomato volatiles. The volatile extracts from field- and artificially-ripe fruits were compared qualitatively as well as quantitatively. The changes which occurred in the volatile components of the fruit at the onset of senescence also were delineated.

A typical chromatogram from field-ripe tomatoes contained 60 peaks. The functional group properties of individual peaks were derived by chemical analysis. The short-chain (C3-C6) alcohols represented 10 per cent, aldehydes and ketones 32 per cent, and hydrocarbons, long-chain alcohols, and esters were in 58 per cent of the total amount of the volatiles from the field-ripe fruits.

Among alcohols and carbonyls, 3-pantanol, 1-nonanal, 1-decanal, and 1-dodecanal and among esters, propyl acetate, geranyl acetate, and cetronellyl butyrate were tentatively identified as volatile compounds of tomato fruit. Linalyl acetate, citronellyl butyrate, and geranyl butyrate were identified for the first time as the components of tomato volatiles.

Comparisons of volatile concentrations of field- and artificially-ripe tomatoes were made. In the latter category of fruits the concentrations of 1-butanol, 3-pentanol, 2-methyl-3-hexanol, 3-methyl-butanal, 2,3-butanedione, propyl acetate, isopentyl butyrate, and other unidentified carbonyls were higher than those observed in the field-ripe fruits. These short-chain compounds, especially the C4-C6 moities, probably are formed in their maximum concentrations during the early stages of maturation. Under the conditions of restricted nutrient availability, sun light, and limited enzymatic activity during artificial ripening, the long-chain compounds are not sunthesized appreciably. The concentrations of some of these short-chain compounds may be to a level of masking the effects of more desirable compounds contributory to ripe tomato aroma. Notably, a pulp from the artificially ripe fruits lacked the characteristic ripe tomato aroma. The concentrations of the long-chain carbonyls and the terpene esters were low in the artificially ripe tomatoes as compared to the field-ripe ones. This may indicate major contribution of these compounds to ripe tomato aroma. An attempt has been made to theorize the mechanisms of the biogenesis of these components of tomato volatiles.

The concentrations of the volatiles from field-ripe and overripe tomatoes were compared. During overripening the amounts of alcohols, aldehydes, ketones, acetates, and propionates generally decreased. However, the concentrations of diacetyl and butyric acid esters increased. It was assumed that at the onset of senescence the metabolic pathways for the formation of diacetyl and butyric acid were highly operative in tomato fruit. The mechanisms of these pathways were postulated.

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