The use of gamma radiation for extractability improvement of bioactive compounds in olive oil wastes

Abstract

Olive pomace is an environmentally detrimental waste from olive oil industry, containing large amounts of bioactive compounds that might be used by the food industry. In this work, the effects of gamma radiation on phenolic compounds and bioactive properties (antioxidant, antimicrobial activities and hepatotoxicity) of Crude Olive Pomace (COP) and Extracted Olive Pomace (EOP) extracts were evaluated. Hydroxytyrosol was the main phenolic compound identified in both olive pomace extracts (24-25 mg/g). The gamma radiation treatment of olive pomace improved at least 2-fold the extractability of phenolic compounds. Moreover, results suggested that gamma radiation at 5 kGy increased the antioxidant activity in EOP, while keeping the ability to protect erythrocytes against oxidation-induced haemolysis. Gamma radiation at 5 kGy could be a suitable technology for olive oil pomaces waste valorization, contributing to enhance extraction of phenolic compounds and bioactive properties, especially when applied on extracted material.

Developing an Olive Biorefinery in Slovenia: Analysis of Phenolic Compounds Found in Olive Mill Pomace and Wastewater

“…A previous report determined that 50-70% of the total phenolic content in olive pomace from the same region was attributed to secoiridoids [31]. In contrast to our results, Madureira et al [39] determined that the major compound present was hydroxytyrosol in extracted and crude pomace from Portugal. This might be due to both differences in the cultivar types screened and environmental factors in the two studies, which would seem to indicate the importance of the evaluation of the phenolic compound content in relation to geographic location and the olive varieties cultivated.…”

Phenolic Compounds from Irradiated Olive Wastes: Optimization of the Heat-Assisted Extraction Using Response Surface Methodology

“…This industry generates large amounts of wastes, where many potentially interesting compounds remain. Olive pomace is rich in bioactive compounds that can be divided in several classes: simple phenols (e.g., tyrosol and hydroxytyrosol) and their derivatives, benzoic and cinnamic acid derivatives (e.g., gallic acid, syringic acid, caffeic acid, p-coumaric acid, verbascoside), flavonoids (e.g., apigenin, luteolin, rutin) and secoiridoids (e.g., oleuropein and oleuropein aglycone isomers) [1][2][3]. Although olive oil wastes can have a negative impact to the environment when discharged without treatment, the recovery of these compounds increases the sustainability of the sector, obtaining high added-value products with low production costs and reducing the environmental risk.…”

“…Numerous studies have reported the extraction of bioactive compounds from olive pomace [1,3,[7][8][9]. The extraction of these compounds can be performed by using conventional or emerging technologies, which can be advantageous since they take reduced extraction time, accelerate heat and mass transfer, increase the extraction selectivity and purity, and use safer solvents comparing to the conventional ones [10,11].…”

“…Ionizing radiation, a clean and environmentally friendly technology, has proven to be capable of improving phenolic extraction and antioxidant activity on industrial wastewater [16], fresh fruits such as cherry tomatoes [17], raspberries [18,19] and strawberries [20], and dried medicinal plants [21]. More recently, the potential of gamma radiation as an enhancer for phenolic compounds extraction and antioxidant capacity has been shown, with the application of low doses (5 kGy), enough to increase the extractability of the main phenolic compounds from olive pomace by 2.4-fold compared to non-irradiated samples [1].…”

“…The current study aims to explore the extraction of some phenolic compounds from olive pomace by heat-assisted extraction (HAE) using a circumscribed central composite design (CCCD) testing different conditions, namely the percentage of ethanol (0-100%), extraction times (20-120 min) and temperature (25-85 • C). The olive pomace samples used in this work were the irradiated ones for which the best results in a previous work of the authors were obtained [1]. The characterization of the individual phenolic compounds was performed, summarized and modeled by Response Surface Methodology (RSM) in order to understand the combined effects of operating variables and to maximize the responses analyzed.…”