46F-9 |
Effect of thermal processing on the nutritional value of tomatoes |
R. H. LIU, V. Dewanto, X. Wu, and K. Adom. Department of Food Science, Cornell University, Stocking Hall, Ithaca, NY 14853 Processed fruits and vegetables have been considered to have lower nutritional value than their fresh commodities. Our group reported vitamin C in apples contributed less than 0.4% of total antioxidant activity indicating most of the activity comes from other phytochemicals, such as phenolics. Therefore, processed fruits and vegetables may retain their antioxidant activity. Our objectives were: 1) to determine the content of total phenolics, flavonoids, vitamin C, and lycopene; 2) to measure the total antioxidant activity of raw and heat-treated tomatoes. Phytochemicals were extracted using 80% acetone. Phenolics and flavonoids were measured by spectrophotometer. Lycopene was determined by HPLC. Antioxidant activity was measured by Total Oxyradical Scavenging Capacity (TOSC) assay. The raw tomatoes had 133.8 ± 5.6 mg vitamin C/g tomato. After heating at 88°C for 2, 15, and 30-min, the vitamin C content significantly dropped to 120.1 ± 3.9, 113.1 ± 1.3, and 94.47 ± 3.34 mg vitamin C/g tomato, respectively (p<0.01). The raw tomatoes contained 201.1 ± 4.1 mg trans-lycopene/100g tomato. After heating at 88°C for 2, 15 and 30-min, the trans-lycopene content significantly increased to 310.5 ± 3.8, 545.2 ± 2.2 and 531.5 ± 5.2 mg trans-lycopene/g tomato (p<0.01). The antioxidant activity of raw tomatoes was 4.13 ± 0.36 mmole vitamin C equivalents/g tomato. With heat treatment at 88°C for 2, 15 and 30-min, the total antioxidant activity significantly increased to 5.29 ± 0.26, 5.53 ± 0.24 and 6.70 ± 0.25 mmole vitamin C equivalents/g tomato, respectively (p<0.01). There were no significant changes in both content of phenolics and flavonoids with thermal processing. Our findings indicate thermal processing increased total antioxidant activity of tomatoes. This information may have a significant impact on consumers' food selection by increasing their consumption of fruits and vegetables.
Session 46F, Nutrition
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