In a significant advancement for the olive oil industry, the integration of high vacuum technology into a novel assisted extraction system is revolutionising virgin olive oil (VOO) processing. This innovative technique, recently tested at a lab-scale pilot plant, has unveiled its profound impact on the physicochemical properties of olive paste and oil, resulting in enhanced VOO quality.
The use of high vacuum technology brought about remarkable changes in the mechanical and structural attributes of olive cells, substantially improving the coalescence of oil droplets. This was attributed to the significant cellular and intracellular mass transfer during the extraction process, as confirmed by cryo-scanning electron microscopy (Cryo-SEM) analysis.
One of the primary objectives of this research was to evaluate the effects of high vacuum-assisted extraction on the quality characteristics of VOOs derived from three different cultivars, all processed at varying malaxation temperatures. The findings were profound, with a noteworthy increase in the phenolic content, ranging from 25.2% to 48.6%. Concurrently, the levels of volatile compounds responsible for VOO flavor exhibited a decline in correlation with malaxation temperature.
Preliminary tests assessing the influence of high vacuum on VOO quality, conducted at elevated malaxation temperatures, demonstrated a substantial increase in phenolic compounds. The data indicated percentage increases of 33.2%, 40.1%, and 50.1% for VOOs obtained at 40 °C, 50 °C, and 60 °C, respectively. This significant enhancement was attributed to the combined effects of high vacuum and high temperature, both facilitating the release of abundant phenols from fruit tissues. Additionally, the synergy between pressure and high temperature improved the liquid mass transfer and the solubility of phenolic compounds into the oil phase. The absence of oxygen, facilitated by the high vacuum, inhibited the enzymatic degradation of phenolic compounds by polyphenoloxydase (PPO) and peroxidase (POD).
In contrast, the concentrations of volatile compounds responsible for VOO flavor experienced significant reductions, particularly in the categories of aldehydes, alcohols, and esters. The high vacuum-assisted extraction process was shown to have a substantial stripping effect on these volatile molecules due to intense evaporation and condensation processes, leading to the extraction of the aqueous phase from the olive paste.
The results highlighted the necessity of lower malaxation temperatures (no higher than 30°C) to preserve VOO aroma effectively. Subsequent trials using lower kneading temperatures confirmed the trend of increasing phenolic composition, demonstrating that the impact of high vacuum was more pronounced than the influence of temperature alone.
This novel extraction technique was not limited to one olive cultivar. It was applied to olives from the Peranzana and Coratina cultivars as well, and the phenolic compositions of their VOOs exhibited similar increasing trends, although the extent of the increase varied depending on the genetic origins of the fruits. In summary, the application of high vacuum during malaxation significantly enhanced the phenolic content of VOOs, with increases ranging from 202 mg/kg to 407 mg/kg.
Notably, the application of high vacuum did not result in any significant changes in the legally regulated quality parameters, such as free fatty acids, peroxide values, K232, K270, and ΔK, compared to control VOO samples from various cultivars.
However, the reduction in volatile compounds due to the high vacuum-assisted extraction process appears to be cultivar-dependent. The decline in volatile compounds responsible for the desirable sensory attributes of VOO was particularly pronounced for ethanol, ethyl acetate, and acetic acid, which can contribute to off-flavors. Smaller reductions in these volatile compounds were observed at lower malaxation temperatures, minimising the adverse effects on VOO quality.
In conclusion, the implementation of high vacuum-assisted extraction has demonstrated a positive impact on VOO quality, notably increasing phenolic compounds while decreasing volatile compounds, especially at lower malaxation temperatures. Further research is warranted to assess the potential industrial-scale application of this technique, its impact on extraction yield, and its potential implications for VOO quality, especially concerning volatile and phenolic fractions. The findings open new horizons for the olive oil industry, promising enhanced product quality and stability.
- Research by: Agnese Taticchi a, Sonia Esposto a, Gianluca Veneziani a, Antonio Minnocci b, Stefania Urbani a, Roberto Selvaggini a, Beatrice Sordini a, Luigi Daidone a, Luca Sebastiani b, Maurizio Servili a
- a ~ Department of Agricultural, Food and Environmental Sciences, University of Perugia, Via S. Costanzo, 06126 Perugia, Italy
- b ~ BioLabs, Institute of Life Sciences, Scuola Superiore Sant’Anna, Piazza Martiri della Libertà 33, I-56127 Pisa, Italy
Read more: https://doi.org/10.1016/j.foodchem.2020.128369
About Olive Oil Vacuum Extraction Processing Plants
The malaxing group can consist of several malaxers which are sealed and are equipped to work under vacuum. When the olives are crushed the paste feeds into the tank thereby filling the tank whilst the vacuum system is removing the air in contact with the paste. Thus creating the environment for the paste to malax for longer durations without air and minimising the risk of oxidation.
- The Sintesi’s low-oxidation, vertical malaxing tanks minimise the paste’s exposure to environmental factors that lower quality by causing oxidative stress, maintaining the quality of your oil as much as possible. Available in models in a mono gramola (single malaxer) for 150 & 400 models and in a modular plant with twin malaxers for 200 & 350 models. More about: Sintesi Olive Oil Processing Plants
- The Cultivar Series start at a production capacity of up to 500kgs per hour through to 3T/hr with a single decanter. More about: Cultivar Olive Oil Processing Plants
Amanda Bailey on Olives by The Olive Centre 