Effects of Steaming and Stir-Frying on Physicochemical and Antioxidant Properties of Tomato Skin, Pulp and Seed

Teng, Xin Yee (2018) Effects of Steaming and Stir-Frying on Physicochemical and Antioxidant Properties of Tomato Skin, Pulp and Seed. Final Year Project (Bachelor), Tunku Abdul Rahman University College.

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Abstract

Tomato (Lycopersicon esculentum) is the major source of antioxidant compounds, therefore is linked to few health benefits such as reduces the risk of cancers and cardiovascular diseases. Tomato can be consumed raw or cooked, whereby some prefers the tomato pulp without skin and seed. This study was carried out 1) to study the physico-chemical and antioxidant properties of tomato skin, pulp and seed 2) to compare the effects of steaming and stir-frying on physicochemical and antioxidant properties of tomato skin, pulp and seed. Fresh tomato was used as standard reference. Results showed that tomato skin, pulp and seed were not significant different (P>0.05) in pH and total soluble solids (TSS). pH of tomato skin, pulp and seed decreased significantly after steaming and stir-frying. TSS of tomato skin, pulp and seed decreased significantly after steaming, but surprisingly increased significantly after stir-frying. In this case, fresh tomato skin had the highest lycopene content (2.37±0.14 mg lycopene/100kg FW), total phenolic content (TPC) (83.46±0.32 mg GAE/100g), total flavonoid content (TFC) (23.29±0.42 mg CE/100g), 2, 2-diphenyl-1-picrylhydrazyl (DPPH) radical scavenging activity (54.5±39.89%) and 2, 2'-azinobis (3-ethylbenzothiazoline-6-sulfonic acid) diammonium salt (ABTS) radical scavenging activity (28.7±14.91%) compared to fresh tomato pulp and seed. After heat treatments, ascorbic acid content (ACC) of tomato skin, pulp and seed decreased. Lycopene content of tomato skin pulp and seed also decreased after stir-frying, but increased after steaming. TPC of tomato skin and pulp, ABTS radical scavenging activity of tomato skin, pulp and seed increased significantly after stir-frying. When steaming time increased from 3 minutes to 8 minutes, TPC of tomato skin and seed, TFC and DPPH radical scavenging activity of tomato skin, pulp and seed decreased. As conclusion, tomato skin exhibited better physicochemical and antioxidant properties compared with tomato pulp and seed. Stir-frying treatment improved the tomato nutritive properties.