& Human Nutrition, Michigan State C. E. PANTOSandP. MARKAKIS University, East Lansing, MI 48823 A Research Note ASCORBIC ACID CONTENT O F ARTIFICIALLY RIPENED TOMATOES INTRODUCTION TOMATOES are a good source of ascorbic acid. In fact, the 6.5 million tons of tomatoes produced annually (1971) in this country could provide approximately one-third of the recommended dietary allowance for Americans. An average value for the ascorbic acid content of tomatoes is 23 mg per 1OOg of fresh fruit (USDA, 1963). In a previous communication (Malewski and Markakis, 197 1) we reported that four cultivars of tomatoes grown in the field reached their highest ascorbic content about 6 wk after anthesis (flower opening) and just before the entire fruit turned red. Except for processing or local use, however, tomatoes are harvested at an earlier stage of development, usually mature-green, and shipped to large markets where they are ripened. In this note we report on the ascorbic acid content of tomatoes ripened off the vine. Two specific reports on the effect of storage on the ascorbic content of unripe tomatoes are those by Scott and Kramer (1949) and Craft and Heinze (1954). Both groups used the Rutgers variety in their studies but the first group reported loss of ascorbic acid during storage of green-mature tomatoes at 70Â°F and riper tomatoes at 35-50âF, while the second group found no pronounced change in the ascorbic acid content of mature-peen tomatoes stored at 32O, 40Â°, 50Â°, 65 and 75OF for periods up to 14 days. MATERIALS & METHODS Table 1 -Ascorbic acid content (mg/lOOg fruit) of two tomato cultivars harvested mature-green and ripened at four different temperatures Cultivar 71-816 Temp. oF 55 Days in storage 71-817 analyzed for ascorbic acid by the 2,6-dichloroindophenol method (AOAC, 1970). Three titrations on a composite liquid sample were applied. The replicate titrations differed by less than 5% from each other. An analysis was also made on tomatoes left on the vine until they turned almost fully red and tomatoes left 1 wk longer. growth and ripening used in this study, contained one-fourth to one-third more ascorbic acid when they were ripened on the vine rather than artificially. This finding should not be surprising since other varietal characteristics (aroma, taste, etc.) of fruits develop to a different degree when ripening occurs on the plant rather than artificially. RESULTS & DISCUSSION THIRTY 4-in. seedlings of the tomato cultivars No. 71-816 and 71-817, supplied by the Horticulture Dept. of this University were planted on June 25, 1971 on the University farm. Individual blossoms were tagged a month later and tomatoes were harvested when a whitish area appeared around the blossom end of the green fruit, about 5 wk after anthesis. The tomatoes were stored in stainless steel cabinets thermostatically controlled at 55â, 60â, 65â and 70â F and with relative humidity of 86-92%. At 0, 2, 4, 6, 8 and 10 days from the day of harvesting three tomatoes were randomly sampled and THERE WAS a decline in the ascorbic acid content of the tomatoes with time of storage at all temperatures and for both cultivars (Table 1). Regarding the progress of ripening, on the sixth day of stor90% of the fruit age, approximately stored at 70Â°F was fully red, 80% of the fruit at 65âF, 50% of those at 55Â°F and 40% of those at 40â F. The color of the tomatoes stored at the two lower temperatures continued to turn red up to the tenth day, while the texture remained firm; some loss in firmness was observed in the tomatoes stored at the higher temperatures beyond the sixth day. Tomatoes left on the vine and analyzed when they were almost fully red (40 days from anthesis) contained 24.8 and 25.2 mg/lOOg fruit for cultivars No. 71-816 and 71-817, respectively. One week later, the fruit on the vine were overripe and contained 19.2 and 18.8 mg/lOOg, respectively. It may be concluded that table-ripe tomatoes of the cultivars, and under the conditions of During December, 1972, 2-lb samples of tomatoes ripened artificially at three different commercial ripening establishments (as deduced from the labels) were obtained from local food stores; they contained 14.4, 14.6 and 14.8 mg of ascorbic acid per 1OOg of fruit.
Journal of Food Science – Wiley
Published: Mar 1, 1973
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