Abstract
The impact of the olive oil refining process on major antioxidant compound levels was evaluated by means of UHPLC analysis of lampante olive oils collected at different stages of the refining procedure (degumming, chemical and physical flash neutralization, bleaching, and deodorization). For this purpose, the evolution of the tocopherol fraction was investigated by means of the UHPLC-FL method, while the influence of the refining process on the total hydrolyzed phenolic content was assessed by measuring hydroxytyrosol and tyrosol levels after acid hydrolysis of the phenolic extracts. Refining was found to have a marked effect on total hydroxytyrosol and tyrosol contents, as they are completely removed in the early steps of the refining procedure. In contrast, the variation trends of tocopherols are not always clear-cut, and significant decreases in content from 7% to 16% were only revealed during refining in four out of nine samples. In addition, five of the nine refined oils showed final tocopherol concentrations higher than 200 mg/kg, the limit imposed by international standards regarding the content of such compounds in commercial olive oils. This study supports the need for a revision of the International Olive Oil Council (IOC) standard relative to the limit established for tocopherol addition to refined oils to avoid possible legal and economic trade issues.
Highlights
Extra virgin and virgin olive oils are obtained solely through physical means by mechanical or direct pressing of the olives
Council (IOOC), refined olive oil is the olive oil obtained from lampante olive oils by refining methods that do not lead to alterations in the initial glyceridic structure
Samples 7, 8, and 9 are characterized by a free acidity close to the maximum level established by the International Olive Oil Council (IOC) trade standard for edible virgin olive oil [1], which in this case included ordinary virgin oil with the upper free acidity limit of 3.3%
Summary
Extra virgin and virgin olive oils are obtained solely through physical means by mechanical or direct pressing of the olives. They are not subjected to any treatment other than washing, decantation, centrifugation, and filtration, and they may be consumed without refining. A significant amount of oil produced in the Mediterranean area (over 20% of total production) is of such poor quality that it must be refined in order to be fit for human consumption [2]. Other minor substances that can affect the quality of the oil, such as phospholipids, pigments, peroxides, Foods 2020, 9, 292; doi:10.3390/foods9030292 www.mdpi.com/journal/foods
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