Processing of Tomato Byproducts for Recovery of Value-Added Compounds and Bioethanol Feedstock

Consumer perception of industrial processes and food production are more focused on food quality, human health, environmental safety, and energy security. Hence, effort has been given toward adding value to wastes of agri-food industries. A team of researchers from various universities, led by Mouna Kehili of University of Sfax, aimed to develop a process that uses tomato by-products of a Tunisian industry for the recovery of value-added compounds.

The developed process combined supercritical CO₂ extraction of carotenoids within the oil fractions from tomato seeds (TS) and tomato peels (TP), followed by a batch isolation of protein from the residues. The remaining lignocellulosic matter was then submitted to a liquid hot water (LHW) hydrolysis and can be used for bioethanol production.

The experiments extracted oleoresin, lycopene, and β-carotene from TP and oil, lycopene and β-carotene from TS. Protein extraction yields of 13.28% in TP and 39.26% in TS, revealed that the two are also rich sources of essential amino acids. LHW treatment showed that a temperature of 160°C was the most appropriate for cellulose and hemicellulose hydrolysis from TP and TS.

These results indicate that tomato by-products can be a good source of lycopene-rich oleoresin, tomato seed oil and good quality protein as well as lignocellulosic matter with potential for bioethanol production.