Date of Award
Master of Science
Plant and Soil Science
AN ABSTRACT OF THE THESIS OF Travis Killion, for the Master of Science degree in Plant, Soil, and Agricultural Systems, presented on April 4, 2014, at Southern Illinois University Carbondale. TITLE: LYCOPENE AND ASCORBIC ACID CONTENT OF FRESH TOMATOES BASED ON GENOTYPE, MATURITY STAGE AND COLD STORAGE INTERVAL MAJOR PROFESSOR: Dr. S. Alan Walters Tomatoes are one of the most widely consumed vegetables and provide a major source of antioxidants to human diets around the world. Since this vegetable is consumed in such high quantities, the nutritional qualities of the tomato fruit were determined based on the tomato's genetic makeup, the stage at which it was harvested, and length of time in cold storage. Therefore, field and storage studies were conducted during the 2012 and 2013 growing seasons at the SIUC Horticulture Research Center in Carbondale. Three field experiments were conducted to determine ascorbic acid (AA, also commonly known as vitamin C) and lycopene content of fresh tomato fruit based on cultivar, harvest stage and time in cold storage. The first experiment evaluated 20 tomato cultivars, while `Rocky Top' tomato was grown using standard production practices and harvested at different stages (mature-green, breaker, turning, pink, light red, and red) to determine the effect of harvest stage on the resulting lycopene and AA content of a red-ripe fruit. Harvested fruit were stored at room temperature (21º C) until they had developed to the red ripe stage and were then immediately evaluated. The effects of short-term cold storage on the lycopene and AA content of red-ripe harvested `Rocky Top' tomato fruit were also determined; tomatoes were placed in cooler at 4º C, with samples retrieved at 0, 1, 2, 3 and 4 weeks. Results indicated that cultivars differed (P ≤ 0.05), with smaller-sized tomatoes having ii higher AA content than larger-sized cultivars. The AA content ranged from 13.4 to 29.8 mg per 100 g of tomato fruit, with higher amounts being observed in the smaller tomato varieties (`Red Currant' and `Sugar Plum'). Lycopene analysis indicated that there were also significant differences amongst cultivars, and the analyses indicated differences between the 2012 and 2013 growing seasons. Higher lycopene content was found in the red varieties, with lower amounts found in lighter colored tomatoes, especially those that were orange colored. In 2012, lycopene content ranged from 4.80 to 100.39 μg/g in tomato fruit, while in 2013, values ranged from 41.4 to 83.7 μg/g. The short-term cold storage evaluation determined that both AA and lycopene concentration decreased over time. For AA and lycopene, a 43% and 24% loss occurred in `Rocky Top' tomato fruit, respectively, after 4 weeks in cold storage. For the tomato stage of maturity experiment, tomatoes harvested at the red-ripe stage had the greatest AA concentrations (0.187 mg/g), with a gradual decline occurring based on the ripeness of the fruit when it was harvested. Fruit that were harvested at a more ripe stage had greater AA concentrations compared to those harvested at lesser ripened stages, with red ripe tomatoes that developed from fruit harvested at the green maturity stage having the least AA content (0.116 mg/g). Similar to AA, lycopene concentrations were higher in tomatoes harvested closer to the red-ripe stage and steadily declined in tomatoes harvested at earlier stages of development, with lowest values observed in red-ripe fruit that developed from mature green tomatoes. Based on the results from this study, tomatoes vary significantly among cultivars, harvest stage, and time in cold storage for both AA and lycopene content. Marketing tomatoes based on antioxidant content has not been widely utilized, but may help local growers explore a different approach to selling tomatoes and to increase profits and customer bases.
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