Changes in Olive Paste Composition During Decanter Feeding and Effects on Oil Yield

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The effect of olive paste moisture on both oil extraction yield and phenolic content and profile from extractable olive oil is studied at the lab‐scale by stressing physical and biochemical phenomena through gradual dilution of freeze‐dried olive paste at a wide range of moisture levels. Olive fruits of Frantoio and Leccio del Corno cultivars are freeze‐dried immediately after harvesting and then milled. Gradual dilution of the obtained freeze‐dried olive pastes allows obtaining olive pastes at moisture 0–60%, from which olive oil samples are immediately extracted. The experiments show that oil extraction yield and phenolic transfer yield increase in extractable oil and reach a maximum (i.e., phenols up to ≈1200 mg kg−1 for Frantoio cultivar) at olive paste moisture values lower than typical values of the olive paste during milling of whole olive fruits. Then, these yields decrease when the olive paste moisture gradually continues to ride above that value. The data also indicate that olive paste moisture plays a crucial role on enzymatic phenomena affecting phenolic profile of the extracted oils and confirms the hypothesis that lignans, absent or linked to other molecules into the fruits, are released or biosynthesized during oil extraction thanks to the co‐presence of enzymes and water. Practical Applications: The results point out that olive paste moisture appears to be as essential in controlling extra virgin olive oil processing as time, temperature and air exposure. Processing procedures along the olive oil chain able to reduce the olive fruit's moisture, may complement the technological innovations for improving oil extraction and phenolic transfer yields. For example, suitable blends of olive batches with different moisture content could be used to control the olive paste moisture and, consequently, the extra virgin olive oil quality. Small mills able to produce express olive oil from olive paste waffles of ≈1 kg, were recently proposed in the market: results of this study also suggest the possibility to dry olives for obtaining dried olive paste waffles suitable to produce small amounts of express olive oils with the selected qualitative characteristics after rehydrating them at the suitable moisture content. Phenolic content in olive oils extracted from lyophilized and rehydrated olive paste is affected by the percentage of water and reach maximum values at moisture content lower that 40%.

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Moisture in Rehydrated Olive Paste Affects Oil Extraction Yield and Phenolic Compound Content and Profile of Extracted Olive Oil

Cecchi

Breschi²,

Migliorini³

et al. 2019

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“…There is an increasing body of scientific literature in the field of extra virgin olive oil processing. The aim is to maximize product quality and identify reliable tools that can modulate quality and preserve, at the same time, extraction efficiency . Among the conventional processing steps (washing, crushing, malaxation, centrifugal extraction and clarification, oil filtration) malaxation seems to be crucial.…”

Section: Introductionmentioning

confidence: 99%

Ethanol From Olive Paste During Malaxation, Exploratory Experiments

Masella¹,

Guerrini²,

Angeloni³

et al. 2018

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Ethanol is a precursor of ethyl esters in olive oil. Its presence is generally ascribed to microbial degradation of damaged olives. At the same time, it is an anaerobic metabolite that naturally accumulates in olive fruit during ripening. As the possible link with olive processing is poorly studied, this laboratory‐scale experiment measures gaseous ethanol in the headspace above olive paste malaxated in sealed conditions. Malaxation take place in the presence or absence of oxygen, using sanitized or untreated olives. The findings show that ethanol accumulates in the headspace in oxygenated trials, reaching roughly 80 μmol kg−1 of olive paste. Under anoxic conditions ethanol accumulation is ten times higher, while olive treatment is not significant. Ethanol kinetics during malaxation are modeled as a biexponential system in which two components are simultaneously present, originating from parallel reactions at different constant rates. The first is the ethanol present in the olives and gradually released in the headspace. The second is ethanol neoformation under anoxic conditions. Under oxygenated conditions, the first component predominates, while under anoxic conditions, the opposite holds. Practical Application: Online monitoring of gaseous ethanol above olive paste during malaxation could easily be implemented in olive oil processing plants. Ethanol kinetics could indicate the presence of unwanted anoxic conditions and help in setting appropriate oxygen levels in the kneaded paste. Future studies may find a link between ethanol kinetics in the malaxation headspace, and the occurrence of ethyl esters in oils. If this is the case, operators would be able to fine‐tune the process to avoid unwanted effects. Ethanol is an anaerobic metabolite that naturally accumulates in olive fruit during ripening. Gaseous ethanol is found to be released from the olive paste during malaxation (sealed conditions). Furthermore, under anoxicity, the ethanol release is roughly ten times higher in response to the absence of oxygen, that is, cell anaerobic respiration take place.

“…It is well-known that VOCs are affected by several operating factors. The first relate to "in-field" factors, such as the environment, agronomy, genetics, timing, and the type of harvesting; then there are "out-of-field" factors, such as the transport and storage of fruit, [8] operating conditions during extraction, [6,9,10] and oil storage, packaging and transport conditions. [11] VOC concentrations are low in unbroken olives.…”

Section: Introductionmentioning

confidence: 99%

Demonstration of the Effectiveness of a Pilot, Variable Speed Crusher Featuring an In‐Line Oxygen Dosing System

Angeloni

Guerrini

Corti

et al. 2022

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At the industrial scale, improvements to extra virgin olive oil (EVOO) processing are an important opportunity to increase both added‐value, and the product's organoleptic and chemical parameters. Concerning all the operations used during EVOO extraction, crushing and malaxation have an effect on the extraction efficiency and minor components composition extremely significant. In this context, a pilot industrial‐scale crusher is designed and developed that can control the amount of oxygen that is dosed directly into the produced olive paste. In this study, the effectiveness of this new technique, combined with different crushing speeds on EVOO quality, is evaluated. It is demonstrated that supplying oxygen to the paste enriches the volatile fraction, the mean increase is about 30% for the compounds associated to positive sensory notes, while the concentrations of the compounds associated to sensory defects are stationary on 5.2 mg kg−1. Practical Applications: This result is confirmed by a sensory analysis, notably an increase in fruity intensity. It is also shown that crushing speed affects the extraction of compounds such as biophenols, and increases the bitter taste. Increased bitterness is detected for samples crushed at 3500 rpm compared to those crushed at lower speed (mean 5.7±0.3 compared to 4.5±0.4).