Towards New Sustainable Squalene Resources: Extraction from Apulian “Aged Extra-Virgin Olive Oil Sludge” (AEVOO-S). A Comparison Between Organic Solvent and Supercritical Fluid Techniques

Valorisation of agro-industry organic wastes has gained importance in the last decades since it pursues two major goals: environment protection and economic profit. Squalene that represents one the most important natural antioxidant for pharmaceutical and cosmeceutical industry, can be recovered from olive oil production wastes, playing a prominent role to substitute of the shark liver oil as main squalene resource, with great benefits from the marine species protection. The “Aged Extra Virgin Olive Oil-Sludge” (AEVOO-S) a less studied olive oil waste contains squalene in a good concentration depending by the starting Extra Virgin Olive Oil (EVOO) quality (cultivar, extraction processes) and storage conditions. In the present work, fresh EVOO, aged olive oil (AEVOO) and isolated sludge have been characterized and compared in some chemico/ physical properties that confirm the applicability of this waste as a further alternative squalene source. Organic solvent under different conditions and supercritical-CO2 extraction of squalene methodologies, were evaluated in order to optimize its recovery. The results showed that at room temperature, chloroform extracts the highest squalene amount (up to 500 mg/100 g of sludge) but with low selectivity (high amount of free fatty acids were also detected) whereas Microwave Assisted Extraction using n-hexane as solvent, provided high squalene yield (456 mg/100 g of sludge) but with less free fatty acid. Due to the high viscosity of the semi-solid sludge, supercritical carbon dioxide does not show the high squalene extraction ability showed using oils. Graphical Abstract: [Figure not available: see fulltext.].