Abstract
Virgin olive oils from the fruits of Croatian autochthonous varieties Oblica, Lastovka and Levantinka were characterized for the first time. Headspace volatiles were analyzed by HS-SPME/GC-FID/MS. The main volatiles were C6 compounds. The most abundant was (E)-hex-2-enal (62.60%–69.20%). (Z)-Hex-3-enal was not found in Lastovka oil, while Levantinka oil did not contain hexanal. Tocopherols, chlorophylls and carotenoids were determined by HPLC-FL. Levantinka oil was characterized by the highest α-tocopherol level (222.00 mg/kg). Total phenolic contents (TPs), as well as antioxidant activity (DPPH assay) of the oils hydrophilic fractions (HFs) were assessed by spectroscopic methods. The antioxidant activity of Oblica oil HF was the most pronounced (0.91 mmol TEAC/kg) and the HF contained the highest TPs amount (212.21 mg/kg). HFs phenolic composition was determined by HPLC-DAD. The main identified phenols were secoiridoids dominated in Oblica oil: decarboxymethyl ligstroside aglycone (p-HPEA-EDA up to 158.5 mg/kg), oleuropein aglycone (3,4-HPEA-EA up to 96.4 mg/kg) and decarboxymethyl oleuropein aglycon (3,4-DHPEA-EDA up to 93.5 mg/kg).
Highlights
Virgin olive oil (VOO) has been a valuable vegetable oil extracted from fresh and healthy olive fruits (Olea europeae L.) by mechanical and other physical methods
The acidity, peroxide value (PV), K232 and K270 of investigated VOOs were assessed by EU method (Table 1)
Considering other C6 compounds it can be seen that (Z)-hex-3-enal was not found in Lastovka oil, while Levantinka oil did not contain hexanal
Summary
Virgin olive oil (VOO) has been a valuable vegetable oil extracted from fresh and healthy olive fruits (Olea europeae L.) by mechanical and other physical methods (washing, decantation, centrifugation or filtration). Extra VOO is appreciated worldwide for its taste and flavor that is colored by various volatile compounds: aldehydes, alcohols, esters, hydrocarbons, ketones, furans and others [7] It has been stated [8] that C6 compounds, the major components of VOO headspace, mainly contribute to green odor notes. These compounds are produced by lipoxygenase-mediated oxidation of polyunsaturated fatty acids containing cis-cis-penta-1,4-diene structure during the crushing and malaxation steps of the oil production [9]. (4) HPLC-DAD targeted phenolics analysis of the hydrophilic oil fractions (HFs) and assessing the HFs antioxidant activity (DPPH assay)
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