CARBOHYDRATE CONTENT OF TOMATO FRUIT

Abstract

The carbohydrate content of mature tomato fruit has received considerable attention since Atwater and Bryant (1) indicated the total sugar content to be about 3.39 per cent, and the starch less than 0.1 per cent, on the fresh basis. In a later publication of the same series containing revised data, Chatfield and Adams (6) gave the average reducing sugar content as 3.37 per cent. Myers and Croll (11) reported the reducing sugar content of two samples of tomatoes to be 3.39 and 2.91 per cent, and the total sugar content 3.47 and 3.25 per cent. Bell, Long, and Hill (2) determined the available carbohydrate content of two samples to be 2.6 and 3.0 per cent., respectively. Lawrence and McCance (9) have placed it at 2.4 per cent. Rosa (13, 14) has presented a study of the composition of tomatoes at different stages of maturity. For the mature fruit, the reducing sugar content of five samples varied from 2.63 to 3.80 per cent. For two of these the sucrose content, by invertase inversion, was 0.04 and 0.11 per cent. The starch content, by diastase inversion, varied from 0.012 to 0.52 per cent, for the five samples. For the same two samples upon which sucrose determinations were made the values for acid-hydrolyzable material, by hydrolysis with 5 per cent, hydrochloric acid, were 0.180 and 0.212 per cent, respectively. Benoy and Webster (3) have reported that the total and reducing sugar concentrations were equal. They reported values of 2.43 per cent, for each, and 0.069 per cent, of starch on the fresh basis. Bigelow and Stevenson (5) and Bigelow and Fitzgerald (4) have studied the chemical composition of commercial tomato products prepared in the eastern tomato-growing sections of the United States. Their values for reducing sugar content of filtrates from pulps averaged about 4.20 per cent. Cruess, Saywell, and Hark (8) have given preliminary data on the composition of California tomatoes. The present investigation was undertaken in order to secure a more complete knowledge of the carbohydrate composition of California tomatoes. The plan has been to study the composition of composite samples of both the entire fruit and the several more or less distinct botanical regions of the fruit. Determinations have been made of the reducing sugars, sucrose, starch, and acid-hydrolyzable material and the dextrose-levulose ratios.