The Impact of Mild Frost Occurring at Different Harvesting Times on the Volatile and Phenolic Composition of Virgin Olive Oil

Abstract

The organoleptic characteristics of virgin olive oil (VOO), together with its nutritional and health properties, have led the olive tree to be cultivated beyond the Mediterranean basin, reaching latitudes with colder climates, with minimum temperatures below 0 °C and with a higher probability of early frosts. The freezing of olives generates destruction within the tissues and promotes degradation reactions. In this study, the impact of mild frost occurring at different harvesting times on the composition of volatiles and phenolic compounds in VOO were investigated. Arbequina variety olives were harvested at different stages of ripening. Half of the olives were subjected to oil extraction and the other half were frozen at −3 ± 1 °C for 12 h prior to oil extraction. A significant decrease of phenolic compounds with harvesting time was observed in both types of oils (fresh and frozen olives). Oils from frozen olives presented a slightly higher content of total phenols, except in the advanced ripening stage (September), and a slightly lower content of volatile compounds at all harvesting times. In addition, a higher content of 3,4-DHPEA-EDA was observed in oils from frozen olives, which is attributed to an early action of the endogenous β-glucosidase enzyme on oleuropein in freeze-damaged olive fruits. Principal component analysis and Discriminant Partial Least Square Regression allowed the oils to be classified according to the type of fruit (fresh and frozen) and the month of harvest. This study would indicate that mild frost would have a low impact on the chemical composition of virgin olive oil, although, this depends on the ripening stage.

Effect of refining and pressing temperature on chemical attributes of canola oil produced in Chile

“…The tocopherol profile was determined according to AOCS Ce 8-89 22 as described by Pino et al 23 . A Merck-Hitachi HPLC system equipped with a pump L-6200A (Merck, Darmstadt, Germany), a Rheodyne 7725i injector with 20 µL sample loop, a LiChro-CART Superspher Si 60 column (25 cm × 4 mm id, 5 µm particle size; Merck, Darmstadt, Germany), and a Hitachi Chromaster 5440 fluorescence detector coupled to a computer with Clarity chromatographic software (DataApex, Prague, The Czech Republic) were used.…”

“…Total Phenol Content was determined according to Pino et al 23 . Hydrophilic compounds were extracted from canola oils with a methanol/water mixture (80/20) and then total phenols were determined in an aliquot of the extract by the Folin-Ciocalteau spectrophotometric method.…”

“…Antioxidant capacity was determined by the Hydrophilic ORAC Assay (H-ORACFL), which was carried out according to Pino et al 23 . Using fluorescein as the fluorescent molecule and Trolox (6-hydroxy-2,5,7,8-tetramethylchroman-2carboxylic acid) as standard solutions.…”

Recent Advances in Natural Polyphenol Research

“…Insoluble phenolics are in cell walls, while soluble phenolics are in the plant cell vacuoles [18]. The degree of ripeness during harvest time, pedoclimatic conditions, infections, processing, and storage can affect the polyphenolic content [19]. The phenolic acids (e.g., derivatives of cinnamic acid and benzoic acid), flavonoids (e.g., flavonols, flavanones, flavones, flavanols, isoflavones, and anthocyanins), lignans, and stilbenes are the most naturally occurring classes of compounds (Figure 1).…”

“…The biosynthesis of complex polyphenols is linked to primary metabolism: the flavonoids' ring B and the chromane ring originate from the amino acid phenylalanine, obtained from the shikimate pathway, whereas ring A is formed from three malonyl-CoA units added through sequential decarboxylation condensation reactions [22]. In food, polyphenolic compounds can impact astringency, bitterness, flavor, color, and oxidative stability [19].…”