Olive Paste Research Articles

Shelf life of extra virgin olive oil manufactured with combined microwaves and megasonic waves at industrial scale

Previous research has demonstrated that the innovative application of combined microwaves and megasonic waves for preconditioning olive paste enabled olive oil production in continuous mode, while delivering higher olive oil yields. The present work further examines the impact of these technologies on the chemical and sensory stability of the oils obtained in previous studies, with reference to international extra virgin olive oil standards. Olive oil samples obtained after traditional malaxation (Control), microwave conditioning (MW), traditional malaxation assisted with megasonics (MS), and the combination of both microwave conditioning followed by megasonics (MW + MS) in a commercial olive oil plant at 350 kg/h, were characterised and evaluated across 1 year at 3-month intervals. All oil samples evaluated met the international extra virgin olive oil standard parameters across the shelf life study. Ethyl esters and waxes increased uniformly across storage indicating no effect of MW or MS on fermentation processes during conditioning. The application of these technologies enhanced the phenolic content in the oils across one-year, with fluctuations among technologies, in comparison to the traditional control process (Control < MW ≈ MS ≈ MW + MS). Overall, this study demonstrates that both MW and MS conditioning technologies and their combination, applied industrially, can create higher quality extra virgin olive oils across storage.

Assessment of the olive oil extraction plant layout implementing a high-power ultrasound machine

The objective of this study is to assess the effects of installation and operation of a high-power ultrasound machine (HPU) for the treatment of olive paste by using ultrasound technology in order to evaluate the best way installation and the best definition of the operating conditions of the machine. The study was conducted installing in an industrial olive oil mill a continuous processing ultrasound machine, which used a frequency of 20 kHz able to work at 3200 kg h−1 as feed capacity. Checking of performance has been carried out by the assessment of the different operating and process conditions, assessing in particular the impact of the ultrasound treatment before and after the malaxation phase on performance indicators of the continuous olive oil plant (plant extractability, olive paste rheological characteristic) and on selected chemical properties of the olive oil extracted (quality parameters, antioxidant content, and volatile profiles). In the tested conditions, high-power ultrasound treatment did not produce significant effect on the legal parameters (free acidity, peroxide index and spectrophotometric indexes), while a significant increase in the content of phenolic compounds was generally observed; higher enhancements were more evident when the high-power ultrasound treatment was carried out before the malaxation phase.

CFD Analysis of a Tubular Heat Exchanger for the Conditioning of Olive Paste

The use of a heat exchanger for the conditioning of the olive paste could enhance the olive oil extraction process. Particularly, paste pre-heating could reduce the malaxation time and, most of all, improve the temperature control during this process (e.g., 27 °C). In this study, a three-dimensional computational fluid dynamics (CFD) analysis of a tubular heat exchanger was carried out to better understand the influence of the inlet conditions of the olive paste on thermal and hydrodynamic behavior within it. CFD analysis was performed with SOLIDWORKS Flow Simulation (ver.2016). The heat exchanger consists of a tube-in-tube module, in which the inner tube was fed with the olive paste, while the jacket was filled of hot water. The main aim was that to predict the heat transfer and pressure drop in paste side of the exchanger. Multiple analyses by varying the mass flow rate and inlet temperature of the paste were carried out, and temperature and pressure drop were estimated. The numerical model has proved very useful in identifying the main factors affecting the optimization of the heat exchanger in order to improve the extraction process of the olive paste.

Emerging trends in olive oil fraud and possible countermeasures

A review of most common types of fraud in the olive oil sector has been carried out. The work was supplemented by the results of an international on-line survey of EU and non-EU stakeholders in the olive oil sector. The review confirms that most common infringements (fraud or non-compliance) are the marketing of virgin olive oil as extra virgin, and blends of other vegetable oils (sunflower, corn, palm, rapeseed, etc.) with olive oil being marketing as olive oil. The on-line survey focused on current and future issues facing a range of stakeholders, e.g. exporters, importers, control laboratories. Of seemingly high priority to industry were emerging issues with regards to fraud arising from the addition of deodorized oil and from mixing with oil obtained by a second centrifugation of the olive paste (remolido). On the same line, a questionnaire, addressed to the EU Food Fraud Network National Contact Points, highlighted that the most frequent fraudulent practice is mixing with lower quality olive oils and that EU, non-EU and mix of EU and non-EU oils are the cases which need more control activities in relation to false designations of origin.

Fatty acids profile (GC-FID) and analytical evaluation of Chemlali olive oil according to a combined laboratory scale ultrasounds and microwave extraction

The aim of this work was to investigate the possibility of combination between micro-waves and ultra-sounds in order to determinate their impact on quality parameters, antioxidant capacity and phenolic compounds as well as fatty acid composition. The protocol consisted in microwave followed by a sonication treatment of olive paste for 5, 10 and 15 min. Results showed that the total phenolic content of olive oil increased positively with the increasing time of treatment ranging from 356 to ~ 639 mg GAE.kg−1 of olive oil. On the other hand, the fatty acid profiles of all studied oils were determined by GC-FID. Besides, olive oil obtained after 15 min of microwave olive past treatment followed by 10 or 15 min of ultrasound treatment showed that these oils had the highest value of Z-vaccenic (C18:1n-7) + Oleic (C18:1n-9) acids. These results encourage further developments for a combined continuous microwave and ultrasonic conditioning technology to fasten the olive oil extraction, to enhance total phenolic, chlorophyll as well as carotenoid contents and Fatty acid composition.

Food By-Products to Extend Shelf Life: The Case of Cod Sticks Breaded with Dried Olive Paste.

Recently, the interest in recovery bioactive compounds from food industrial by-products is growing abundantly. Olive oil by-products are a source of valuable bioactive compounds with antioxidant and antimicrobial properties. One of the most interesting by-products of olive oil obtained by a two-phase decanter is the olive paste, a wet homogeneous pulp free from residuals of the kernel. To valorize the olive paste, ready-to-cook cod sticks breaded with dried olive oil by-products were developed. Shelf-life tests were carried out on breaded cod sticks and during 15 days of storage at 4 °C pH evolution, microbiological aspects, and sensory properties were also monitored. In addition, the chemical quality of both control and active samples was assessed in terms of total phenols, flavonoids, and antioxidant activity. The enrichment with olive paste increased the total phenols, the flavonoids, and the antioxidant activity of the breaded fish samples compared to the control. Furthermore, the bioactive compounds acted as antimicrobial agents, without compromising the sensory parameters. Therefore, the new products recorded a longer shelf life (12 days) than the control fish sample that remained acceptable for nine days.

High vacuum-assisted extraction affects virgin olive oil quality: Impact on phenolic and volatile compounds

High vacuum technology has been incorporated into a new assisted extraction system applied to virgin olive oil (VOO) processing, which was tested at a lab-scale pilot plant to evaluate its impact on the physicochemical properties of the olive paste and oil. The vacuum system induced changes in the mechanical and structural properties of the olive cells, improving the coalescence of the oil droplets due to substantial cellular and intracellular mass transfer during the process, as shown by cryo-scanning electron microscopy (Cryo-SEM) analysis. The effects on the quality characteristics of VOOs extracted from three cultivars at different malaxation temperatures were evaluated. A significant increase in the phenolic content, from 25.2% to 48.6%, was observed. The content of volatile compounds responsible for the VOO flavor decreased as a function of malaxation temperature. The reduction of some volatile molecules related to the VOO off-flavor (ethanol, ethyl acetate and acetic acid) was also shown.

Partial De‐Stoning of Olive Paste to Increase Olive Oil Quality, Yield, and Sustainability of the Olive Oil Extraction Process

AbstractStone recovery in the olive oil extraction process can be an opportunity to increase both incomes and environmental sustainability. To this aim a new partial de‐stoning machine (called Moliden) is installed at the first stage of an olive oil extraction plant to investigate its influence on the quality and sustainability of the extraction process. Quantitative and qualitative results are compared with those achieved using a conventional extraction process. Despite the 60% of stone recovered, no significant differences are registered for oil yield and extractability. A high‐quality biomass is recovered by the partial de‐stoner machine, belonging to A1 class quality when compared to the standard of the wood pellet, with the only exception of the moisture content. The partial de‐stoning also improves the extra virgin olive oil (EVOO) quality in terms of hydrophilic phenols resulting in an enhancement of bitter and pungent sensory notes and most of all provides a beneficial effect for human health.Practical Applications: The new concept of partial de‐stoner machine proposed in this work allows reducing the equipment employed in the extraction process of olive oil, since it consists of two sections: crushing and de‐stoning. When compared with a standard unit, which recover pits from pomace, it provides a higher quality stone to be used as a biomass fuel. This leads to economic benefits for the millers and has a significant impact on the environmental sustainability of the process.

Development of a modified malaxer reel: Influence on mechanical characteristic and virgin olive oil quality and composition

Malaxation represents a critical and deeply studied step of the virgin olive oil extraction process due to its influence on yield and quality. Nonetheless, few experimental works have been focused on the mechanical aspects of the malaxer machine itself, with the aim of increasing its performance. In this framework, we investigated the effects of design changes of the rotating parts of the malaxer machine on the oil yield and on the virgin olive oil quality, antioxidants and volatile compounds.The modified reel determined a significant increase in extraction yield, respect to the traditional one, as a consequence of the decrease in consistency index of the olive paste. By the qualitative point of view the extracted oil could be categorized as extra virgin. However, malaxer modification brought to a decrease of the antioxidants and an increase of the oxidative phenomenon, as showed by volatiles originated from oxidative degradation and by the enzymatic activities in olive paste. Nonetheless, the outcomes suggested that a possible reduction of malaxation time by the modified reel could be useful to increase the work capacity and to possibly preserve oil quality.

Quick spectrophotometric methods for antioxidant capacity and phenolic compounds determination: Different physico-chemical treatments of Chemlali olive paste

Quick spectrophotometric methods for antioxidant capacity and phenolic compounds determination: Different physico-chemical treatments of Chemlali olive paste

Antioxidant quantification in different portions obtained during olive oil extraction process in an olive oil press mill.

Different antioxidant compounds are generally transferred from olives to olive oil during the production process. This work characterized the principal total bioactive compounds (tocopherols and phenols) in olives, olive oil and by-products of four cultivars grown in Calabrian areas (southern Italy), considering the effect of harvesting period. Antioxidant capacity, total and individual phenolic compounds were also analysed. Drupes, olive paste, pomace and olive wastewater showed similar phenolic compounds, while olive oil possessed a different composition, suggesting that phenols are not only transferred from drupe to oil, but also they change during oil production. Tocopherols varied among cultivars and harvesting period: generally, they were more abundant in samples produced in the first harvesting period. Qualitative and quantitative differences in phenolic composition and antioxidant activity were significantly found among cultivars in all the matrices. The highest amount of total phenolic antioxidants ended up in olive wastewater with variability due to the olive cultivar, while only a small part of them finished in the oil. This work shows evidence that the availability of bioactive compounds in different portions from the olive oil extraction belong to different varietal origins. In particular, new information was acquired on Ottobratica Calipa, a new olive clone, that produced an olive oil with an interesting antioxidant amount. © 2020 Society of Chemical Industry.

Study of the influence of technological coadjuvants on enzyme activities and phenolic and volatile compounds in virgin olive oil by a response surface methodology approach

Although the use of technological coadjuvants during virgin olive oil extraction helps in maximising the process efficiency, it could influence the characteristics of the final product. So far, why this happens is still not understood. In this context, an influence on the biochemical activities occurring during the malaxation step was supposed, and this hypothesis was verified by a response surface methodology approach. The effect of two independent variables, namely malaxation temperature and amount of coadjuvant, on polyphenol oxidase, peroxidase and lipoxygenase activities as well as on the corresponding phenolic and volatile compounds of the oils was studied. Calcium carbonate enhanced the activities of oxidases leading to a reduction of phenolic compounds, which were negatively correlated with the coadjuvant usage. Micronized natural talc behaved the opposite but had a general weaker influence, often overcome by that of mixing temperature. A significant shift of the olive paste pH toward that optimal for oxidases enzymes was highlighted under the use of calcium carbonate. The findings evidenced a “side effect” of the use of technological coadjuvants in the context of virgin olive oil extraction.

Modified Rotating Reel for Malaxer Machines: Assessment of Rheological Characteristics, Energy Consumption, Temperature Profile, and Virgin Olive Oil Quality.

The properties of food products are the result of changes produced in raw materials as a result of process treatments. In the olive oil extraction process, these changes can be observed as differences in quality, nutritional characteristics, taste, and flavor, and are especially due to the time and temperature of the malaxation phase. These parameters are closely related to the mechanical design of malaxer machines. In this study, a new reel model for malaxer machines was designed. The new model was incorporated into an industrial malaxer machine and experimental tests were carried out to study the effects of two different reel designs (modified and unmodified profile) on the rheological characteristics of olive paste, the energy consumption of the plant, and the temperature profile inside the machine. The main commercial parameters of the produced olive oil were studied, as well as the extraction yield and the extraction efficiency of the plant. The malaxer machine equipped with the modified reel showed better homogenization of the paste, which led to improved heat exchange and rheological properties. The results of this study showed that a specific modification of the rotating reel can improve the performance of the malaxer in terms of improving the viscosity of the paste, 127,157.67 (mPa sn) for the malaxer with the modified reel at the beginning of malaxation, reaching a final value of 64,626.00 (mPa sn) at the end. The unmodified malaxer showed an initial viscosity coefficient of 133,754.00 (mPa sn) and a final value of 111,990.67 (mPa sn). This led to a reduction in malaxing times, an increase in the work capacity of the plant, and a reduction in total energy consumption and slowed down the oxidative phenomena responsible for the decrease in the quality of olive oil.

Evaluation of a multisensorial system for a rapid preliminary screening of the olive oil chemical compounds in an industrial process

In this study, a sensory system, named BIONOTE, based on gas and liquid analyses was used to analyse the headspace of olive oil samples obtained at the end of the extraction process for a preliminary screening of the volatile and phenolic compounds. Olive oil samples were obtained using different olive paste conditioning systems, including microwave and megasound machines at different processing time. The same olives batch was used for the entire test. BIONOTE showed the ability to discriminate between 64 virgin olive oils originated from different technologies or by using different process parameters, as demonstrated by the partial least square discriminant analysis (PLS-DA) models calculated. The percentage of correct classification in different conditions are in a range from 92.19% to 100%. In addition, the research shown that the multisensorial system can provide a preliminary estimation of some volatile and phenolic compounds concentrations detected by laboratory analysis. Data analysis has been performed using multivariate data analysis techniques: PLS-DA cross validation via leave one out criterion. Future perspectives are to further develop BIONOTE in order to increase the number of detected chemical compounds and finally to include the mathematical models obtained in the BIONOTE microcontroller for a rapid chemical characterization of olive oil in the mill.

Comparative Effect of Hammer Mill Screen Size and Cell Wall-Degrading Enzymes During Olive Oil Extraction.

The influence of hammer mill screen size (4.5 and 8.5 mm) and enzyme addition (control and 500 ppm) on olive fruit cell wall breakdown and its consequences in terms of oil recovery and the phenolic content of olive oil was studied at the laboratory scale for “Arbequina” and “Koroneiki” at two different maturities. Water recovery and water-soluble carbohydrates in olive paste after malaxation were measured as an indicator of cell wall breakdown. Smaller screen size and enzymes increase oil recovery for Arbequina with a maturity index of 1.6 (6.3–6.6%); and for Koroneiki at a maturity index of 0.2 (15.0–38%) and 2.6 (1.3–4.3%). For both cultivars, the increase in oil recovery is larger in green fruits compared to more ripe fruit. Water recovery and water-soluble carbohydrates increase with small screen size and the enzyme treatments, even when no increment in oil recovery is observed. The water recovery range was 143–239% for Arbequina and 150–262% for Koroneiki; water-soluble carbohydrate range was 1.8–12.7 g/kg for Arbequina and 0.5–5.4 g/kg for Koroneiki. In general, smaller hammer mill screen size and enzymes increase total phenols in the oil, with a larger difference between control and treatment for green fruit than for the ripe fruit. For Arbequina, increases in total phenol content were in the range of 45–60 and 5–20% at maturity index 1.6 and 3.3, respectively. For Koroneiki, the increases were in the range of 31–121 and 7–9% at maturity index 0.2 and 2.6, respectively. Application of cell wall-degrading enzymes improves the cell wall breakdown caused by hammer mill, leading to higher oil recovery and total phenol content. The magnitude of the effect depends on the cultivar and olive fruit maturity.

Change in some quality parameters and oxidative stability of olive oils with regard to ultrasound pretreatment, depitting and water addition

Ultrasound pretreatment with different times (0, 4, 8, 10 min) on olive paste previous malaxation of olive oil extraction along with depitting and water application procedures were studied. The effects of these procedures on oil yield, quality parameters and oxidative stability have been studied. Therefore, the olive oil yield increase with increasing time of ultrasound treatment. On the other hand, the application of ultrasound did not adversely affect the quality characteristics, as well as the antioxidant activity, when comparing with untreated paste. Furthermore, the oxidative stability data, we can conclude that ultrasound treatment can affect the olive oil oxidative stability. This study could provide useful information for industry to produce olive oil with high yield and quality.

Antioxidants in Extra Virgin Olive Oil and Table Olives: Connections between Agriculture and Processing for Health Choices.

This review focuses on the conditions required to increase and maintain the antioxidant nutrients in both extra virgin olive oil (EVOO) and table olives (TOs) from the agronomic and technological practices to the gastronomy. The main antioxidants of TOs and EVOO are phenol alcohols and acids, secoiridoids, lignans and flavones, all of which possess the ability to prolong the oil’s shelf-life and exhibit healthy properties for humans. The precise detection of secoiridoid derivatives remains the breakthrough for the nutritional and health quality certification of extra virgin olive oils (EVOOs) required for EFSA health claims. To attain the necessary antioxidant quality in both EVOO and TOs, it is necessary to hard focus on the several steps in the production chain, including olive cultivar, agronomic conditions, harvesting methods, and transformation technology. The quality level is maintained if the storage conditions aim to minimize the oxidative processes that occur due to oxygen and light. In terms of minor polar biophenols, there is disagreement on which between the organic or conventional EVOOs show higher concentration values. The strict disciplinary of production of protected designation EVOOs does not ensure higher phenol values in comparison to the artisanal EVOOs. In gastronomy, the EVOOs are preferable to seed oils, particularly during frying vegetable. The EVOOs show higher heat stability, linked both to the fatty acid composition and the phenol content, that is important for preventing fatty acids oxidation. Concerning TOs, the commercial presentation includes olives and olive paste. Both products show a remarkable loss of natural antioxidants after pasteurization and during storage as the thermal treatment mostly impacts on TOs secoiridoids.

Fluid dynamic-based Engineering design of a Full-Scale Device for the improvement of Extra Virgin Olive Oil Yield and Quality by means of Combined Acoustic Cavitation and Thermal Conditioning

After some hesitations, the scientific community is jointly converging on the benefits due to the ultrasound treatment by means of mechanical effects generated by acoustic cavitation phenomena occurring into the olive oil paste proposed initially by Amirante and Clodoveo. In recent works, many authors have now confirmed that this promising emerging technology produces relevant beneficial effects if applied to the extraction process under well-controlled conditions. In the last years, the industrial applications of ultrasound (US) in the Extra-Virgin Olive Oil (EVOO) extraction process are changing the paradigm of the knowledge in this field of interest due to a great effort of the research activity. In the present work, the design of the device by means a Three-Dimensional (3D) Multiphase Computational Fluid Dynamic (CFD) analysis was performed, which describes the ultrasound effects in the olive paste, necessary to control the US waves propagation. Thus, fluid dynamic analysis allowed to predict the flow path in the ultrasound devices, to evaluate the flow parameters of the olive paste inside the SHE and the cavitation phenomenon, with the aim to find an optimal design, capable to ensure the best ultrasounds and mixing effects. Moreover, experimental results demonstrated that the machine can guarantee an actual simultaneous improvement of the olive oil extraction yield, as well as of the product quality. Finally, the results from sensory evaluations are summarized confirming the goodness of EVOO obtained by means of US.

Pulsed Electric Fields for the Treatment of Olive Pastes in the Oil Extraction Process

The aim of this study was to evaluate the ability of pulsed electric field (PEF) technology to improve the extractability and enhance the oil quality in an industrial olive oil extraction process. Using a PEF device on olive pastes significantly increased the extractability from 79.5% for the control, up to 85.5%. The PEF system did not modify the primary legal quality parameters or total concentrations of phenols, aldehydes, and esters. On the contrary, the non-thermal treatment slightly enhanced the dialdehydic forms of decarboxymethyl elenolic acid linked to hydroxytyrosol (3,4-DHPEA-EDA) and tyrosol (p-HPEA-EDA), and decreased the total saturated and unsaturated C5 and C6 alcohols of the PEF EVOO (Extra Virgin Olive Oil) compared to the control test. This study confirmed that PEF technology can improve olive oil extraction and quality.

Cereal foods fortified with by-products from the olive oil industry

The oil industry produces large volume of waste, olive mill waste water (OMWW) and olive paste (OP), which represents a disposal and a potential environmental pollution problem. They are also promising sources of valuable compounds that can be recovered and used. The effects of OMWW and OP addition to bread and pasta, separately and combined, were studied. Both sensory and chemical properties as related to phenols content and antioxidant activity of raw materials, and fortified bread and pasta were evaluated. Results suggested that the enrichment of bread and pasta with OMWW slightly improved the chemical quality without compromising the sensory properties. While, foods enrichment with OP had considerably improved chemical quality, the sensory acceptability was worse due to the bitter and spicy taste of OP. To choose the best cereal food between bread and pasta to be enriched, a mathematical model, the whole quality index (WQI), was used. Bread was better than pasta for re-using olive oil by-products. Between OMWW and OP, the latter was more suitable for food fortification, despite the sensory problems of the enriched product. Also, when the two by-products were combined, the best product continued to be the bread.