PROCESSING TOMATO CULTIVARS WITH FIRMNESS, LONG VINE STORAGE AND HIGH VISCOSITY POTENTIAL

One of the most significant changes in California processing tomato cultivars in the past decade has been the development of machine-harvest types with very firm fruits. Additional advantages of these cultivars are long vine-storage characteristics which allows growers to wait for harvest until virtually 100% of the fruits are ripe and their high viscosity potential, which provides products with greater consistency.

In the mid 1960's G. C. Hanna crossed VF 65, an elongated firm-fruited cultivar developed at the University of California, with two firm-fruited breeding lines from Florida (FLA 1339 and FLA 1346). This cross resulted in several firm-fruited cultivars which were released to processors and seedsmen in 1970. This paper will be a discussion of the characteristics of these firm-fruited tomatoes, their advantages to the processing industry, and the difficulties plant breeders can expect with their use in breeding programs.

The outstanding characteristics of the firm-fruited cultivars results from greater amounts of cell walls (alcohol insoluble solids) in the fruits (Stevens and Paulson, 1976). It is not yet known whether the greater amount of cell walls results because there are more cells present or because of greater cell wall thickness. The cell walls are largely composed of cellulose and pectins, and are a complex mixture of carbohydrates and organic acids.

The principle advantage of the firm-fruited cultivars for growers is their handling and vine storage characteristics. These characteristics have enabled growers to realize more of the total yield potential of the tomato plants. with the older processing cultivars, growers usually started harvest when 80–85% of the fruits were ripe. With the firm-fruited cultivars, they are able to wait until more than 95% of the fruits are ripe because they remain in good condition for a relatively long time after they are fully ripe. This long vine-storage characteristic is due primarily to the greater firmness of these cultivars at the onset of ripening (Ramadan, unpublished data). The rate of fruit softening is no different than the softer cultivars, but because the initial firm-ness is much greater they remain in usable condition for a much longer time period. The firm-fruited cultivars generally have a high level of crack resistance.

For the processor, the chief advantages of the firm fruited cultivars are less broken fruits and lower losses during the handling connected with unloading and washing at the processing plant. These cultivars also give greatly increased case yields of products which are sold on the basis of consistency level. It is possible to make more cases of ketchup from these cultivars than the older ones which had much lower viscosity potential.