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Abstract
Tomato seeds represent a very large waste byproduct from the processing of tomatoes into products such as tomato juice, sauce and paste. One potential use for these seeds is as a source of vegetable oil. This research investigated the oil content of tomato seeds using several extraction techniques as well as an examination of the oil extracts to determine the composition of the minor constituents such as phytosterol and antioxidant composition. The oxygen radical absorbance capacity (ORAC) of the tomato seed oils were also measured and correlated with antioxidant contents. This research demonstrated that tomato seed oil yield was highest using hot ethanol and followed by hot hexane and finally SC-CO2. The SC-CO2 treatment, however, had the highest total phytosterol content as well as highest individual phytosterol content. Sitosterol, cycloartanol, and stigmasterol were the most abundant phytosterols present in the extracts. The highest concentrations of antioxidants were found in the hexane extract. The most abundant antioxidants found in the tomato seed oils were all-trans-lycopene, cis-3-lycopene and β-carotene. ORAC was highest for the hexane extract. Oil yield was inversely proportional to both α-tocopherol and γ-tocopherol content and positively correlated with cis-3-lycopene content. ORAC values were positively correlated with only all-trans-lycopene and cis-3-lycopene demonstrating their role as antioxidants in the tomato seed oil.
Keywords Tomato seed oil * Supercritical carbon dioxide * Accelerated solvent extraction * Phytosterol * Antioxidant * ORAC
Introduction
In 2002, ca. 12 million tons of tomatoes were canned and the commercial processing of tomatoes produces large amounts of waste [1, 2], with between 33 and 40% of the raw tomatoes ending up as processing waste [3, 4]. Seeds and skins constitute the main waste by-product of the tomato processing industry [5, 6]. To maximize profits, tomato processors need to find uses for these waste materials. Tomato seeds have been shown to contain ca. 20% oil [7] with a fatty acid composition of tomato seed essentially like that of low linolenic soybean oil [8]. It has been suggested that tomato seeds would be a good source of salad oil [9].
Tomato seed oil has previously been effectively extracted using supercritical CO2 (SC-CO2) [6, 10]. In addition, SC-CO2 has been used to extract minor constituents from tomatoes, including phytosterols [11], tocopherols [11,...