| Abstract: | A comparative study has been made of the individual non-volatile organic acids in ethanolic extracts of the red and green areas of the walls of tomato fruit showing symptoms of ‘blotchy’ ripening. The titratable and total acidites of the green areas were lower, and the combined acidity higher than those of the red areas. Potassium concentrations in the differently coloured areas did not differ significantly. Concentrations of the dicarboxylic amino-acids, pyrrolidonecarboxylic, malic and citric acids in the green areas were all significantly lower than in the corresponding red areas. Citric acid concentrations were much lower and glutamic acid concentrations higher than those found previously in the walls of uniformly ripened fruit of similar colours. The malic/citric acid ratio in the green areas was approximately double that in the red areas. In both cases values were greater than those normally encountered in evenly ripening fruit. The proportions of the total acidity present as malic acid in the differently coloured areas was strikingly similar to that found in the walls of normally ripened fruit of the same colour and variety. On the other hand the proportion of citric acid was markedly reduced in the ‘blotchy’ fruit walls. It is suggested that low citric acid concentrations combined with the persistence of high polyphenol-oxidase activity may be conducive to ‘blotchy’ ripening of tomato fruit. |
