The application of a novel process based on the hydrothermal treatment of olive oil waste (alperujo) led to a final liquid phase that contained a high concentration of simple phenolic compounds. This study evaluated the effects of time (15-90 min) on the composition of the phenolic compounds isolated at a fixed temperature of 160 °C. Phenolic compounds were extracted with ethyl acetate. Both qualitative and quantitative HPLC analyses of the extracts showed variation of the concentrations of phenolic compounds with time. In addition, new phenols that were not present in the untreated control have been characterized. The antioxidant activities of different phenolic extracts was measured by various assays conducted in vitro: antiradical capacity (using DPPH and ABTS radicals), ferric reducing power (P(R)), inhibition of primary and secondary oxidation in lipid systems, and other tests, such as inhibition of tyrosinase activity. The results show that the phenolic extracts inhibited oxidation in aqueous and lipid systems to a significantly greater extent than the untreated control, and they performed as well as or better than vitamin E in this capacity.

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Strawberries have antioxidant, cardiovascular, and antiproliferative properties. The agroindustrial production of strawberry concentrate generates a food waste after extrudation that is usually landfilled. This strawberry extrudate is a rich source of valuable bioactive compounds such as phenols and sugars. In the present study, industrial thermal treatments currently in use for the valorization of other agricultural wastes were determined to be suitable for the treatment of strawberry extrudate. Thermal treatment conditions in the range of 90 ºC to 200 ºC were studied. Thermal treatment at 150 ºC for 60 minutes without acid addition was the most efficient process based on the solubilization of sugars and phenols as well as the antioxidant capacity of the liquid phase produced. Instead of sending this residual fraction to landfill, such treatment would permit the use of strawberry extrudate as a source for the recovery of valuable bioactive compounds.