Lycopene and Other Bioactive Compounds' Extraction from Tomato Processing Industry Waste: A Comparison of Ultrasonication Versus a Conventional Stirring Method

The tomato (Lycopersicon esculentum) is a prominent fruit in Mediterranean countries with established biological activities for consumers. Given the widespread distribution of the fruit and its large production, the need to utilize the by-products seems imperative. With a view to valorizing the main carotenoid of tomato processing industry waste, lycopene, as well as other bioactive compounds (i.e., polyphenols), the optimization of a green extraction method involving ultrasound-assisted bath extraction (UBAE) was carried out. The results showed that the optimized UBAE technique achieved substantial yields of total carotenoids (420.8 mu g of lycopene equivalents per gram of dry weight (dw)) and total polyphenols (2.62 mg of gallic acid equivalents per gram of dw). Flavonoid naringin (0.48 mg/g dw) and non-flavonoid coniferyl alcohol (0.32 mg/g dw) were the most abundant identified polyphenols. However, comparison with a conventional stirring extraction revealed that the latter technique marked double figures in all assays, including antioxidant activity assays. The study revealed that UBAE was not a preferable technique for recovering carotenoids because of the possible degradation of labile compounds found in tomato processing industry waste. Given that the extraction solvent was pure ethanol, the study established a foundation for the development of a unique lycopene-enriched product in the food industry. It is essential to conduct additional studies using alternative food-grade solvents or other environmentally friendly extraction methods.