Tomato waste extract (Lycopersicon esculentum) as a natural antioxidant in soybean oil under heating

The tomato processing industry generates a large amount of waste, usually composed of peels and seeds. It is known that the tomato is rich in bioactive compounds, mainly carotenoids (lycopene and ?-carotene), however, studies on the functionality of its residues are scarce. Thus, these residues are discarded without the knowledge of possible antioxidant potential. The objective of this work was to determine the stability of bioactive in soybean oil added to the extract of agroindustrial tomato waste under heating.  The extract obtained with ethyl alcohol at the ratio of 1: 5 (w/v) was initially analyzed for total phenolic compounds, lycopene, ?-carotene, and antioxidant activity using the DPPH and ?- carotene / linoleic acid. Subsequently, the extract and the synthetic antioxidants, butylhydroxytoluene (BHT) and tert-butylhydroquinone (TBHQ) were applied in soybean oil, and the treatments subjected to heating in Rancimat (180oC/5 h). The thermoxidated samples were analyzed for the composition of tocopherols by high-performance liquid chromatography (HPLC), phytosterols, and fatty acid profile by gas chromatography (GC). The extract of agro-industrial tomato residues showed moderate results concerning its antioxidant activity, 68% by the DPPH method, and 26.2% of auto-oxidation of the ?-carotene / linoleic acid system. The synthetic antioxidant TBHQ had a greater protective effect on soybean oil when compared to the control, providing greater retention of phytosterols (85%) and tocopherols (93%). Tomato extract can be used as a natural antioxidant in industrialized oils, but with less effectiveness than the antioxidant TBHQ.