It is proposed to describe briefly the rise in popularity of the tomato during the 20th century to become the world's fourth most significant fruit, making an important contribution to human nutrition. The grading standards for fruit used in various major tomato-producing countries will be outlined. A major part of the review will be devoted to describing changes in composition during the maturation, ripening, preservation, and storage of good quality tomatoes especially as regards carbohydrates, organic and amino acids, proteins, steroids, pigments, minerals, and the lipids, volatiles, and other minor constituents. A range within which composition should normally fall will be given. Additionally, the effects on composition of environment, cultivar, nutrition, and physiological disorders inter alia will be described. How new growing methods and genetic manipulation could influence the tomato of the future will also be considered.

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SUMMARY An enzyme that attacks carboxymethyl cellulose may be extracted efficiently from tomato fruit by salt solutions. From a high initial value in small green fruit, activity fell gradually during fruit swelling. With incipient ripeness, the activity increased again and continued to rise to the full red condition. The green areas of “blotchy” ripened fruit showed 40% less activity than the adjacent red tissue. Fruit of tomato species in the sub‐genus Eriopersicon contained considerably more activity than examples from the sub‐genus Eulycopersicon. Firmness measurements on fruit from both sub‐genera were not significantly correlated with the cellulase activities, and from this and other evidence it is concluded that is is not a major factor controlling the softening of at fruit, at least during the ripening period.

The use of colour to separate tomatoes into groups at distinct stages of ripeness is usually a subjective procedure. In an attempt to reduce variability, tomatoes previously sorted by eye into five categories from mature green to full red were reassessed using a tristimulus colour difference meter. Various methods of presenting the samples to the machine for colour testing and of transforming the results were compared, and a formula was developed so that objective limits for each ripening stage could be calculated. In order to obtain matched samples of fruit at any particular stage of ripeness, the instrument can be programmed to reject fruit falling outside the appropriate limits. The colour components of tomatoes of several cultivars chosen subjectively to be at the same stage of ripeness (orange-red) were shown to be related to fruit firmness.

(8,12).

The effects of calcium ions and the cheluting agents EDTA and citrate on the ability of partially-purified polygalacturonase (PG) from ripe tomato fruit to degrade polygalacturonate, preparations of isolated middle lamellae and cell walls (ML-CW), and outer pericarp tissue from tomatoes were examined. The inhibition of degradation by calcium ions was counteracted by the presence of EDTA or citrate, and these chelating agents also reduced the resistance to attack by PG on ML-CW and tomato pericarp tissue. Degradation by PG of ML-CW and pericarp tissue from all ripeness stages was stimulated by chelating agents. Susceptibility of fruit tissue containing the nonripening (nor) gene to degradation by PG was similar to that shown by normal mature green fruit tissue. With increasing maturity of the mutant fruit, resistance to degradation declined, but not as rapidly as with normally ripening fruit. It appears that calcium associated with the ML-CW and its removal regulate the rate and extent of degradation by PG during normal tomato fruit ripening. 'Published with the approval of the Director of the Arkansas Agricultural Experiment Station, University of Arkansas, Fayetteville, AR 72701.