Paolo Amirante

Influence of Different Centrifugal Extraction Systems on Antioxidant Content and Stability of Virgin Olive Oil

Publisher Summary The different centrifugal decanters employed in olive processing influence oil yields, qualitative characteristics such as total phenols and induction time values, and composition of volatile compounds such as aldehydes, alcohols, esters, hydrocarbons, ketones, furans, and other compounds that are responsible for the unique and delicate flavor of olive oil. Total phenols as well as induction time values are higher in oils obtained by the centrifugal decanter of two phases. The induction time is the length of time before the rate of lipid oxidation of an oil sample rapidly accelerates. The induction time of olive oil samples, as measured by the Rancimat instrument, showed a significant correlation to the concentration of total phenolic compounds. Dual-phase decanters work on the same principle as the three-phase decanters, except little or no water is added prior to centrifugation. This allows the retention of more polyphenols and volatiles. The “third-generation” three-phase decanters allow for the improvement of oil yields without compromising the quality of the product. This is the best solution with respect to the two-phase decanters because it is possible to extract the oil without adding water to the process, thus obtaining dry pomace, which is more easily transportable and workable.

Influence of the Crushing System: Phenol Content in Virgin Olive Oil Produced from Whole and De-stoned Pastes

Publisher Summary The mechanical processes used to extract virgin olive oil from olive fruit include the crushing of the olives, malaxation of resulting pastes and separation of the oily phase essentially by pressure or centrifugation. All these operations affect the quality of virgin olive oil. Olive paste preparation is the most important phase of the process when oil is mechanically extracted from the olives. The use of differing machines in olive oil production has inevitable repercussions on the cost-effectiveness of the oil-making process, on the amounts of oil extracted and especially on the quality of the oil obtained. In order to obtain the best virgin olive oil, quality olives must be processed as quickly as possible after harvesting from the trees. Normally they should be delivered to the mill within a day or so of picking, in order to keep down oxidation and acidity. When extracting oil from olives, it is very important to clean them properly first, in order to ensure the levels of hygiene required for a high-quality olive oil product. Once cleaned, the olives must be crushed, in order to make the olive paste that itself is the first stage in extracting the oil. How this is done is crucial for both the quantity and the quality of the olive oil product. Mechanical oil extraction from de-stoned pastes can improve the oil phenolic concentration. The quality characteristics of virgin olive oil also depend on oxidative enzyme reactions that take place in olive paste during the extraction process. Two enzymes, polyphenol oxidase (PPO) and peroxidase (POD), are highly concentrated in the olive kernel. PPO and POD can oxidize phenolic compounds resulting in a reduced phenolic concentration of oil. The de-stoning process, excluding the olive seed before malaxation, partially removes the peroxidase activity in the pastes. This results in an increase in oxidative stability and nutritional value of virgin olive oil.

The Malaxation Process: Influence on Olive Oil Quality and the Effect of the Control of Oxygen Concentration in Virgin Olive Oil

Publisher Summary Malaxing is an extremely important phase in olive oil extraction. During the malaxing phase the olive paste is subjected to a slow continuous kneading, aimed at breaking off the emulsions formed during the crushing process and facilitating adequate coalescence. It is necessary to heat the olive paste at a carefully monitored temperature during malaxation in order to diminish the viscosity of the product and to stimulate its enzymic activity, therefore increasing the extraction yields. This operation facilitates high extraction yields, by helping small oil droplets to coalesce. These can be separated subsequently using a decanter centrifuge. The malaxing process determines the balance between the quality and the quantity of the oil extracted, by varying a range of parameters (time, temperature, and atmosphere in contact with the olive paste), as the olive paste is gradually heated and the enzymes within are activated. All this must be done without affecting the biochemical structure of the olive paste, as this would affect the flavor, shelf-life and nutritional properties of the oil. This operation is one of the critical points in olive oil extraction. Many studies have been carried out to investigate its influence on the olive oil quality. Nowadays the olive oil consumer asks for healthy products. There has been a large increase in demand for high-quality virgin olive oil, attributed not only to its potential health benefits, but also to its particular organoleptic properties. In fact, the sensory quality plays an important role in customer preferences. The operating environment during malaxation affects the volatile and phenolic composition of virgin olive oil and, as a consequence, its sensory and healthy qualities.