The effect of blanketing with CO2, naturally evolved during malaxation of olive pastes, on the quality of virgin olive oil was investigated at lab-scale. The O2 depletion was monitored along with CO2 emission to confirm the previously hypothesized accelerated respiration. Malaxation experiments were conducted for 180 min both in sealed (SC) and in the traditional open-to-air conditions to ascertain whether the oil quality was affected by O2 concentration as afforded by CO2 blanketing. The quality of olive oils obtained at different time intervals was monitored by total acidity, peroxide value (PV), specific extinction coefficients K232 and K270, total chlorophyll and total hydrophilic phenols, and HPLC hydrophilic phenols profile. A rapid decrease in oxygen concentration and a simultaneous increase in CO2 concentration were recorded, confirming the accelerated respiration. The oil produced in SC showed a lower PV and K232 coefficient and a higher chlorophyll (10–17 mg/kg) and hydrophilic phenols (110 mg/kg) concentration. No differences in total acidity and K270 coefficient were observed. The hydrophilic phenols profile indicated that, at least for the Frantoio cultivar and an advanced ripeness state, the maximal extraction is generally achieved already after 20 min. Most of the individual hydrophilic phenols have higher concentrations (up to 50%) in SC.
"In the reality, the malaxation under inert gas is not widely widespread due to the high cost of nitrogen and argon that cannot be ignored (Clodoveo, 2013a). In fact, in order to address this problem, Parenti et al. (2006) suggested to profit by the phenomenon of CO2 emission coupled with the O2 depletion during malaxation under sealed conditions. The last evolution is represented by malaxer equipped with sensors, which are able to measure the temperature of the olive paste and the oxygen concentration in the headspace and inside the olive paste (Amirante et al., 2008; Amirante et al., 2012a). "
[Show abstract][Hide abstract] ABSTRACT: The aim of virgin olive oil elaboration process is to obtain the highest recovery of the best quality oil from the fruits. The aim of the researchers is to understand the key elements that allow to modulate the complex series of physical, physico-chemical, chemical and biochemical transformations in order to develop innovative and sustainable plant solutions able to increase simultaneously both yield and quality of product. The basic principles applied also in the newest olive oil industrial plants still follow the technical knowledge which have been empirically learned by humans thousands of years ago. In fact, it is well known that three factors, mixing, water adding and warming, are the three macroscopic driving forces able to favour the separation of the oily phase from the mass of crushed olives. In this consolidated scenario, can new elements emerge? The whole process should be considered more than a simple extraction of the oil present in fruit cells, but a complex elaboration of a product, which is depleted and enriched of both constitutive and neo-synthesised compounds through complex phenomena only in part discovered. In fact, while it is evident that numerous studies have been conducted to elucidate the behaviour of olive paste during virgin olive oil extraction process, a key conclusion is that the current level of understanding can be improved further by means the development of more rigorous researches with more focused targets aimed to understand the rheological changes, the coalescence phenomena, the changes in hydrophobic and hydrophilic phenomena, the partition equilibrium of minor compounds between aqueous and oily phases and, last but not least, the favourable and unfavourable enzymatic reactions. This paper provides an analysis of the present research field and its strengths and weaknesses are discussed. Potentially important future directions for research are also proposed.
Journal of Agricultural Engineering 10/2014; Vol 45(No 2):49-59. DOI:10.4081/jae.2014.193
[Show abstract][Hide abstract] ABSTRACT: The relationship between olive paste malaxation temperature and the concentration of olive oil hydrophilic phenols (HP), i.e. simple phenols, secoiridoids and lignans, was investigated. Malaxation experiments were performed at laboratory scale for 45 min at 21, 24, 27, 30, 33 and 36 °C. A significant (p <0.05) increment of total phenols concentration was found with a maximum at 27 °C, whereas for higher temperatures (30–36 °C) a progressive decrement was observed. A similar pattern was recorded approximately for all the secoiridoid compounds, i.e. a quasi-linear increment of concentrations with increasing temperature until 30 °C, followed by a marked decrease in correspondence with the higher malaxation temperature (33 and 36 °C). The amount of simple phenols increased linearly with increasing temperature and no decrements were observed up to the maximal temperature investigated (36 °C), while no significant differences were found for lignans. A small increment of peroxide values and total chlorophyll was recorded as a function of the increasing malaxation temperature, whereas no differences were observed in the free acidity. The results highlight that there is not a univocal relationship between HP concentration and malaxation temperature. An equilibrium between degradation (chemical and biochemical oxidation and hydrolysis) and transfer (partitioning) phenomena was hypothesized.
European Journal of Lipid Science and Technology 08/2008; 110(8):735 - 741. DOI:10.1002/ejlt.200700307 · 1.81 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: The sensory and health properties of virgin olive oil (VOO) are highly related to its volatile and phenolic composition. Oxygen control in the pastes during malaxation may be a new technological parameter to regulate enzymatic activities, such as polyphenoloxidase, peroxidase, and lipoxygenase, which affect the phenolic and volatile composition of VOO. In this work, we monitored CO2 and O2 concentrations during industrial-scale olive paste malaxation with various initial O2 concentrations within the malaxer headspace. Results show that the O2 concentration in the malaxer headspace did not affect CO2 production during processing, whereas a strong influence was observed on the changes of the phenolic composition of olive pastes and VOOs, with high correlation coefficient for the total phenols (R = 0.94), especially for oleuropein and demethyloleuropein derivatives (R = 0.81). In contrast, aroma production during malaxation was minimally affected by the O2 concentration in the malaxer headspace.
Journal of Agricultural and Food Chemistry 11/2008; 56(21):10048-55. DOI:10.1021/jf800694h · 2.91 Impact Factor
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