Ultrasound-assisted enzyme catalyzed hydrolysis of olive waste and recovery of antioxidant phenolic compounds

Abstract

Abstract The ultrasound-assisted enzyme hydrolysis (UAEH) procedure for extraction of phenolics from olive waste (OW) was established. The optimized conditions obtained with response surface methodology (RSM) were pH 5.75, treatment 40 min and temperature 55 °C, the yield obtained reached to 4.0%. The extraction kinetics model was fitted well to the ln ( C t / C 0 ) = kt , and the rate constants ( k ) increased with the increased in the extraction temperature. Moreover, the values of k were higher and the activation energy was lower than ultrasound treatment alone. The thermodynamic parameters indicated the extraction process was easier under the UAEH. Compared with the petroleum ether and n-butyl alcohol, ethyl acetate extract fraction had high phenolic content (64.4 mg/g), especially hydroxytyrosol and tyrosol (17.2 mg/g and 14.1 mg/g), and exhibited excellent antioxidant activities in DPPH·, ABTS + ·and FRAP assay. These finding revealed that OW could be used for a enrich source of natural phenolic compounds for development of food industry. Industrial relevance Olive waste (OW) has been widely paid attention as sources of high-added value compounds, such as phenolic which can be obtained by the several methods. And phenolic extract as a food additive can not only improve the sensory quality of food, but also can enhance antioxidant capacity in fatty food matrices. Moreover, the use of this extract has better economic benefits than synthetic additives usually used in food industry. In this study, a novel green, simple and efficient technology was employed to extract the phenolic compounds, which was suitable for large-scale industrial use. The results indicated that ultrasound-assisted enzyme hydrolysis (UAEH) has significant potential in the extraction process of phenolics from OW exhibiting higher phenolic yield in shorter extraction times.