DETINNING IN CANNED TOMATOES CAUSED BY ACCUMULATIONS OF NITRATE IN THE FRUIT

ABSTRACT— The 1965 experimental crop of Floradel variety tomatoes accumulated no nitrate and removed only about 15% of the tin from their containers in a 2-yr storage period. The 1966 Florida crop of Homestead 24 variety tomatoes accumulated from about 50–80 ppm in the fruit and removed about 70% of the tin from their cans. All fertilizer application variables except the lowest resulted in about the same level of nitrate accumulation. The nitrate in most of these variables was exhausted in about 6 mo and the rate of detinning leveled off soon after. The correlation between loss of nitrate and tin removal was significant at the 5% level. Detinning in these cans approached a "problem level' in that about 70% of the tin was removed in 18 mo. In the 1965 tomato crop at Ohio State University there was no apparent connection between the levels of applied nitrogen and the nitrate accumulated in the fruit. In the 1966 Ohio tomatoes, the treatments with no applied nitrogen accumulated less nitrate in the fruit than the other treatments with varying levels of nitrate fertilization. The differences among the detinning histories of the various treatments followed in a general way the differences in nitrate accumulation. Detinning in individual cans varied between extremely wide limits. There were no differences apparent among the treatment variables in the 1965 crop. In the 1966 tomatoes the zero applied nitrogen treatment consistently showed less detinning than the others. In both the 1965 and 1966 crops the nitrate in the canned samples was exhausted after about 2 mo of storage. Essentially all of the detinning in these tomatoes occurred during the first 6 mo. Regression equations from pooled results of field studies and work on nitrate fortification of non-aggressive tomatoes suggest that an initial nitrate concentration of the order of 100 ppm can constitute a rapid detinning problem in tomatoes in a 303 can having a tin coating weight of 1.00 Ib/bb.