Modulating the bitterness of Empeltre olive oil by partitioning polyphenols between oil and water phases: Effect on quality and shelf life.

Bitterness is a positive sensorial attribute of olive oil that mainly depends on phenol concentration. However, excessive bitterness may be unpleasant for consumers. The aim of this investigation was to evaluate if partitioning polyphenols between oil and water phases could modulate the bitterness of an Empeltre olive oil containing a phenolic concentration higher than the typical content for this olive oil variety. The linear relationship observed between the percentage of oil in the extraction system and the percentage of phenols removed from the oil permitted estimating the olive oil-to-water ratio required to reduce the concentration of phenols for a given value in order to modulate Empeltre olive oil bitterness. Olive oils after liquid-liquid extraction did not develop any negative sensory attributes, and their physicochemical parameters were not substantially affected. Liquid-liquid extraction using water as a solvent is a procedure capable of effectively reducing the total phenol compounds of Empeltre extra virgin olive oil and, as a consequence, of reducing its bitterness intensity without affecting the highest commercial category determined by the parameters legally established by European Community regulations just after extraction and during nine months of storage.

Assessing the efficacy of PEF treatments for improving polyphenol extraction during red wine vinifications.

The influence of the electric field intensity and pulse width on the improvement of total polyphenol index (TPI) and colour intensity (CI) during extraction in an ethanolic solution (30%) and during fermentation-maceration has been investigated in different grape varieties: Grenache from two harvesting times, Syrah and Tempranillo. The aim of this study was to develop a procedure to establish the PEF treatment conditions that cause enough permeabilization in the skin cells of different grape varieties to obtain a significant improvement in the vinification process in terms of increment on the polyphenol content or reduction of maceration time. Results obtained in this investigation indicate that extraction of polyphenols in a solution of ethanol (30%) for 2 h could be a suitable procedure to know if the PEF technology is effective for improving extraction of polyphenols from the grapes during vinification and to determine the most suitable PEF treatment conditions to obtain this objective. Improvement in the extraction during vinification only was observed with those grapes and under treatment conditions in which the improvement of the polyphenol extraction was higher than 40%. Other interesting observation from this research is the highest efficacy of PEF when treatments of the same duration are applied using longer pulses. Therefore, in a continuous process, where the flow processed is determined by the frequency applied by the PEF generator, it is possible to increase the processing capacity of the PEF installation. INDUSTRIAL RELEVANCE: Benefits from PEF treatment of the grapes before the maceration step in the vinification process have been demonstrated. Nevertheless, the characteristics of the grapes may change in different vintages and grape varieties. Therefore, it is of high importance to be able to determine the optimum PEF conditions in order to obtain the desired benefit during the vinification. The rapid method developed permits to determine PEF process parameters before the application of the PEF treatment with the objective of facilitating the phenolic extraction and therefore, reducing the maceration time. In these cases, it would be possible to remove the skins from the rest of the wine earlier, and therefore, increase the processing capacity of the winery.

Olive oil quality and ripening in super-high-density Arbequina orchard.

BACKGROUND: The aim of this work was to evaluate the evolution of the quality of extra virgin olive oil obtained from a super-high-density Arbequina orchard, under a drip irrigation system, throughout the ripening process. For this objective, physicochemical, nutritional and sensory parameters were studied. In addition, the oxidative stability, pigment content and colour evolution of olive oil were analysed during the ripening process. RESULTS: Free acidity increased slightly throughout the ripening process, while peroxide value and extinction coefficient decreased. Total phenol content and oxidative stability showed a similar trend, increasing at the beginning of ripening up to a maximum and thereafter decreasing. α-Tocopherol and pigment contents decreased with ripening, leading to changes in colour coordinates. Sensory parameters were correlated with total phenol content, following a similar trend throughout the maturation process. CONCLUSION: By sampling and monitoring the ripeness index weekly, it would be possible to determine an optimal harvesting time for olives according to the industrial yield and the physicochemical, nutritional and sensory properties of the olive oil.