Effect of processing technology on chemical, sensory, and consumers' hedonic rating of seven olive oil varieties

Quality of oil extracted by cold press from Nigella sativa seeds conditioned and pre-treated by microwave

Black cumin (Nigella sativa) seed (BS) oil has received much interest in the food and pharmaceutical industries due to its valuable nutritional properties, but this oil has low oxidative stability. The effect of microwave pre-treatment at 0 to 2.5 min and conditioning with different buffers at pH 3 to 9 of BS, before oil extraction by cold press, were investigated. The oil extraction yield was higher; acid value (AV) and peroxide value (PV) were lower in the oil extracted from seeds, which were first microwaved and then moisturized and vice versa. BS with pH 3, microwave time of 1.25 min, and moisturizing level of 5%, which gave oil extraction yield of 27.2%, AV of (2.9 mg NaOH/g oil), and PV of (8.3 meq O2/kg oil), was selected as an optimum sample and its quality changes were investigated during storage compared with the oil extracted from the control sample (without any pre-treatment). In conclusion, the oil extracted from the pre-treated BS had higher bioactive components and lower AV and PV during the storage; therefore, microwave radiation and pH adjustment before oil extraction from BS by cold press are recommended.

Fatty Acid and Phenolic Profiles of Virgin Olive Oils from Local and European Varieties Planted in Lebanon

In Lebanon, olive oil is an integral part of its history and culinary traditions. However, the quality of this product, originating from different growing regions of the country, is rarely addressed. The objectives of this study were to compare the fatty acids and phenolic profiles of virgin olive oils produced from two local and eight European varieties, and to use these profiles as a tool for their characterization. Seventy-six samples were collected from two olive-growing regions of Lebanon and at two harvesting times. Fatty acid composition was determined by gas chromatography with a flame ionization detector, total phenols was determined by spectrophotometry and individual phenols by high performance liquid chromatography with diode array detector. All samples were also analyzed using near infrared spectroscopy. The experimental data were collected in numerical matrices and treated by chemometric methods. The results showed the significant effect of the geographical origin, the olive variety and the harvesting time on the ripening and industrial yield of the olives and on the major fatty acids and phenols of olive oil. Moreover, the used chemometric methods allowed the discrimination of European olive varieties based on their high contents of oleic acid, oleacein and oleocanthal.

Application of Dispersive Liquid-Liquid Aerosol Phase Extraction to the Analysis of Total and Individual Phenolic Compounds in Fried Extra Virgin Olive Oils

Seventeen extra virgin olive oil samples from Valencian Community (Spain) were submitted to a domestic-frying process (180 °C) during different degradation times (5, 10, 30, 60, 120 min). A dispersive liquid-liquid aerosol phase extraction by using a methanol/water (50:50) extracting solution was used to isolate the polyphenol fraction. Total phenolic content (TPC) was determined, whereas the determination of seven individual target polyphenolic compounds (hydroxytyrosol, tyrosol, oleuropein, vanillic acid, p-coumaric acid, ferulic acid, and vanillin) was carried out by using ultrahigh-performance liquid chromatography coupled to a tandem mass spectrometer. Statistically significant differences in the TPC values were found for Blanqueta and Manzanilla samples from different harvesting years. The domestic-frying process impacted the TPC and the individual phenolic compounds content. Thermal treatment for 2 h gave rise to a 94% decrease in the TPC. A first-order kinetic model was suitable to accurately describe the degradation of the individual phenolic compounds.