Two-phase Olive Oil Extraction Research Articles

Effect of two-phase olive pomace acidification on odor prevention and kernel oil acidity reduction as a function of storage duration

The adoption of two-phase olive oil extraction processes has led to a significant increase in the amounts of two-phase olive pomace produced each year. This material is typically led to kernel oil extraction facilities that are forced to store the excessive amounts until treatment. During storage, malodorous compounds, like 4-ethylphenol, are formed that are then released to the atmosphere during drying, causing serious problems in a radius of several kilometers. At the same time, increased microbial activity in the stored pomace deteriorates kernel oil, diminishing its value. This deterioration is expressed as increased kernel oil acidity. In this work, the evolution of 4-ethylphenol concentration and kernel oil acidity as a function of storage duration and waste acidification were examined. The concentration of 4-ethylphenol in the unmodified two-phase olive pomace seems to be maximized after 23 d of storage, while kernel oil acidity reached a plateau of 10% after 70 d. Acidification at pH 2 prevented the production of 4-ethylphenol and kept kernel oil acidity at 5% for more than 100 d of storage. The results presented herein are a step towards understanding the processes taking place during two-phase olive pomace storage and exploring ways of minimizing their effects.

Biogas Potential of the Side Streams Obtained in a Novel Phenolic Extraction System from Olive Mill Solid Waste.

The olive oil production is an important industrial sector in many Mediterranean areas, but it is currently struggled by the necessity of a proper valorisation of the olive mill solid waste or alperujo. The alperujo is the main by-product generated during the two-phase olive oil extraction, accounting for up to 80% of the initial olive mass. The alperujo is a source of valuable compounds, such as the pomace olive oil or highly interesting phenolic compounds. In the present research, a novel biorefinery approach has been used for phenolic compounds recovery. However, the extraction of these valuables compounds generates different exhausted phases with high organic matter content that are required to be managed. This study consists of the evaluation of the anaerobic biodegradability of the different fractions obtained in a novel biorefinery approach for the integral valorisation of alperujo. The results show that the different phases obtained during the biorefinery of the alperujo can be effectively subjected to anaerobic digestion and no inhibition processes were detected. The highest methane yield coefficients were obtained for the phases obtained after a two-months storages, i.e., suspended solids and liquid phase free of suspended solids, which generated 366 ± 7 mL CH4/g VS and 358 ± 6 mL CH4/g VS, respectively. The phenol extraction process reduced the methane yield coefficient around 25% due to the retention of biodegradable compounds during the extraction process. Regardless of this drop, the anaerobic digestion is a suitable technology for the stabilization of the different generated residual phases, whereas the high market price of the extracted phenols can largely compensate the slight decrease in the methane generation.

New Liquid Source of Antioxidant Phenolic Compounds in the Olive Oil Industry: Alperujo Water

The current management of alperujo as the main solid by-product from the two-phase olive oil extraction system has led to the appearance of a new liquid effluent that until now was treated together with the alperujo itself. The composition and antioxidant properties of its bioactive components at different depths of the pond were studied using colorimetric and HPLC with UV and MS detectors, DPPH, reducing power and rancimat. The concentration of suspended solids varied between 1.71 and 8.49 g/L, total fat was between 0.74 and 1.47 g/L, and total phenols were found between 3.74 and 4.11 g/L, which included hydroxytyrosol, 3,4-dihydroxyphenylglycol and tyrosol as the main phenols. Two types of extracts were obtained through two industrial systems with ethyl acetate and by chromotography, with an average content in total sugars of 2.1% and 3.16%, total phenols of 17.9% and 28.6% and hydroxytyrosol of 51.5 and 79.0 mg/g of extract, respectively. The activity presented by the chromatographic extract was higher in terms of free radical sequestering capacity, reducing power and the inhibition of lipid oxidation. Obtaining bioactive extracts would improve the formulation of food with natural components and at the same time would be the first step in a biorefinery to improve the management of the new effluent.

Utilization of olive pomace as a source of bioactive compounds in quality improving of toast bread

Olive oil pomace is produced as by-product with a large quantity during olive oil processing. It is a promising source for polyphenolic compounds and fibers which could be used in food industry. In this work proximate chemical analysis of olive pomace (two-phase olive oil extraction) was studied. Also, seven extracting solvents were tested in extracting the phenolic compounds from the olive pomace (OP). Total phenolic, flavonoids, and flavonols contents of the different extracts were determined. In addition to, the antioxidant activity of the phenolic extracts was investigated using 2, 2-diphenyl-1-picrihydrazyl (DPPH) to assess the efficiency of the extracting solvents. The obtained data rivaled that protein, fat, ash and fiber contents of OP were 2.48, 2.33, 1.33 and 20.37% (FW), respectively. It is clear that the OP contains a large quantity of fibers and it had cellulose content about 40.7% of the fiber content. Furthermore, the total phenolic content was varied in the different extracts and ranged from 8.29 to 36.24 mg GAE g -1. While, the total flavonoids were ranged from 2.23 to 12.52 mg QE g-1. Methanol and water (80:20) recorded the highest antioxidant activity with EC50 of 1.373g/g DPPH while, the acetone extract recorded the lowest antioxidant activity with EC50 of 8.052g /g DPPH. Toast bread was fortified with the cellulose isolated from OP at three replacement levels of 2, 4, and 6% and the results showed that there were no significant differences between control sample and the sample fortified with 2% cellulose in most of sensory characteristics tested. Addition of pomace cellulose at replacement level of 2% enhanced the texture of the bead and was more acceptable than the control. The results concluded that olive pomace is a good source for dietary fibers and polyphenolic compound which could be used in the food industry.

The use of industrial thermal techniques to improve the bioactive compounds extraction and the olive oil solid waste utilization

Abstract The development of thermal treatments is helping to optimize the management of waste generated by the two-phase olive oil extraction system. A new treatment reactor, based on the steam explosion system, has been scaled up to the industrial level and offers several physical and chemical advantages. The reactor has been adapted to work into the pomace oil extractors. Chemical advantages include the efficient solubilization of simple phenols, like hydroxytyrosol, and sugars in the liquid fraction, and a significant reduction of humidity and toxicity of the residual solid fraction, in which cellulose and oil are concentrated, making the solid residual waste more suitable for subsequent bioprocess applications. All of these parameters will lead to the widespread use of steam treatment in the near future to improve the management and obtain the maximum exploitation of this byproduct.

Treatment of Two-Phase Olive Mill Wastewater and Recovery of Phenolic Compounds Using Membrane Technology.

The semi-solid wastes (pomace or alperujo) produced in the two-phase olive oil extraction process contains extremely high organic load and phenolic substances. Efficient treatment of such kinds of wastes using membrane filtration, should be sought to reduce the hazardous effects to the environment. On the other hand, phenolic compounds can be isolated and purified up to a level of commercial exploitation using the membrane technology. Firstly, the extraction process with mixtures of water and ethanol was optimized by testing extraction parameters (e.g., solvent’s mixture, duration, and temperature) at laboratory scale. Next, extraction was conducted using larger volumes and the treatment was continued in a pilot membrane filtration system, consisted of ultrafiltration (UF), nanofiltration (NF) and reverse osmosis (RO) membranes. The extracted solution from the olive oil pomace was fed to the pilot membrane filtration system, where all fat, lipids, and solids were removed while the phenolic compounds were concentrated in the retentate streams of NF and/or RO. Total phenolic content (TPC) at the RO’s concentrate stream was 225 mg/L and at the final effluent was lower than 10 mg/lt. The chemical oxygen demand (COD) value at the final effluent was much lower (~280 mg/L) than in the feed stream (>32,000 mg/L).

Comparison between different liquid-liquid and solid phase methods of extraction prior to the identification of the phenolic fraction present in olive oil washing wastewater from the two-phase olive oil extraction system

Phenolic compounds from olive mill wastewater (OMW), are characterized by a strong antioxidant activity. At the same time, they represent an environmental problem because they are difficult to degrade. The purpose of this work was to identify these biologically active compounds in the OMW from two-phase olive oil production in order to convert a polluting residue into a source of natural antioxidants. After optimizing the extraction process of phenolic compounds using liquid-liquid extraction (LLE) and solid phase extraction (SPE) methods, it was determined that the most appropriate sequence comprised a previous centrifugation to remove the lipid fraction, followed by liquid extraction with ethyl acetate or SPE. The most important compounds identified in olive oil washing wastewater (OOWW) were tyrosol, hydroxytyrosol and succinic acid; whereas the ones in the wastewater derived from the washing of the olives (OWW) were cresol, catechol, 4-methylcatechol, hydrocinnamic acid and p-hydroxy-hydrocinnamic acid.

Study of Waste from Two-Phase Olive Oil Extraction as an Additive in Ceramic Material

The properties of ceramic materials are intimately related to a variety of factors, among them shaping procedure and sintering time. These factors condition, the microstructure and properties of the materials developed. Our study has formed materials from clays commonly used in the area of Bailén (Jaén) and wet pomace proceeding from the extraction of olive oil. The materials were shaped through extrusion. In this study, raw materials have been characterized and studied interesting properties of sintered materials, such as compressive strength, water absorption, open porosity or bulk density. The study concluded that the addition of wet pomace from olive oil industry into traditional brick entails a saving of raw materials and reducing the environmental impact generated by their manufacture. The best results are obtained for the samples with waste content of 3 wt %.

Boundary flux optimization of a nanofiltration membrane module used for the treatment of olive mill wastewater from a two-phase extraction process

The boundary flux theory was used to modelize the performance of a nanofiltration (NF) membrane in the treatment of the effluents exiting a two-phase olive oil extraction process, in particular olive mill (OMW) and olives washing (OWW) wastewater streams. The results obtained from the pressure-cycling experiments exhibit a boundary flux pattern with very low long-term fouling for all analyzed feedstocks. This observation is confirmed by the low values of the sub-boundary fouling parameter (α) obtained by the fitting of the experimental flux data measured during batch-run operation to the boundary flux model. Reduced long-term fouling (28.6–33.3%) occurred during NF operation of the effluents after the proposed secondary treatment, which comprised pH-temperature flocculation followed by ultraviolet (UV) photocatalysis with ferromagnetic-core nanocatalyst and an ultrafiltration separation step (UF). Otherwise, a decrease of long-term fouling in the range of 57.1–60% was observed by using the secondary-treated 1:1 (v/v) mixture of OMW and OWW as feedstock. Moreover, processing both feedstocks to the complete secondary treatment led to increased feed recovery rates (85–90%) and boundary flux values (12.3–19.6Lh−1m−2). Finally, the standard limits to reuse the purified effluents for irrigation were successfully achieved.

Assessing the impact of biotransformed dry olive residue application to soil: Effects on enzyme activities and fungal community

Dry olive residue (DOR), a solid by-product of the two-phase olive oil extraction system, is rich in organic matter and nutritionally important compounds. However, the agronomic application of this residue may impact negatively on the soil ecosystem due to its toxic components. The aim of the present study was to investigate the impact of raw DOR, Coriolopsis floccosa-transformed DOR and Fusarium oxysporum-transformed DOR on soil biological properties. To do this, soil enzyme activities, fungal community size (quantitative PCR) and fungal community structure (DGGE of 18S rRNA gene) were measured. The impact of biotransformed and nonbiotransformed DOR applications to soil depended on two factors: the variable sensitivity of the soil to the residue's composition and the duration of exposure to amendments. The application of this biotransformed residue enhanced soil enzyme activities (phosphatase, β-glucosidase and urease) with respect to soil amended with nonbiotransformed residue. The quantification of the 18S rRNA gene copy number indicated that the different amendments stimulated relative abundance. DGGE analysis showed that the amendments produced changes in fungal community structure although variations in fungal diversity were only detected after C. floccosa-transformed DOR addition at 60 days, probably due to the enhancement of species such as Chaetomium globosum and Chalazion helveticum.

Effects of Dry Olive Residue Transformed by Coriolopsis floccosa (Polyporaceae) on the Distribution and Dynamic of a Culturable Fungal Soil Community

Dry olive residue (DOR) is an abundant waste product resulting from a two-phase olive oil extraction system. Due to its high organic and mineral content, this material has been proposed as an organic soil amendment; however, it presents phytotoxic and microtoxic properties. Thus, a pretreatment is necessary before its application to soil. Among the strategies for the bioremediation of DOR is treatment with ligninolytic fungi, e.g. Coriolopsis floccosa. This work aimed to assess the diversity of culturable fungi in a soil of the southeast Iberian Peninsula and to evaluate the short-term impact of untransformed and C. floccosa-transformed DOR on soil mycobiota. A total of 1,733 strains were isolated by the particle filtration method and were grouped among 109 different species using morphological and molecular methods. The majority of isolates were ascomycetes and were concentrated among three orders: Hypocreales, Eurotiales and Capnodiales. The soil amendment with untransformed DOR was associated with a depression in fungal diversity at 30 days and changes in the proportions of the major species. However, when C. floccosa-transformed DOR was applied to the soil, changes in fungal diversity were less evident, and species composition was similar to unamended soil.

Reuse of olive mill effluents from two-phase extraction process by integrated advanced oxidation and reverse osmosis treatment

In this work, complete reclamation of the olive mill effluents coming from a two-phase olive oil extraction process (OME-2) was studied on a pilot scale. The developed depuration procedure integrates an advanced oxidation process based on Fenton's reagent (secondary treatment) coupled with a final reverse osmosis (RO) stage (purification step). The former aims for the removal of the major concentration of refractory organic pollutants present in OME-2, whereas the latter provides efficient purification of the high salinity. Complete physicochemical composition of OME-2 after the secondary treatment was examined, including the particle size distribution, organic matter gradation and bacterial growth, in order to assess the selection of the membrane and its fouling propensity. Hydrodynamics and selectivity of the membrane were accurately modelized. Upon optimization of the hydrodynamic conditions, the RO membrane showed stable performance and fouling problems were satisfactorily overcome. Steady-state permeate flux equal to 21.1Lh−1m−2 and rejection values up to 99.1% and 98.1% of the organic pollutants and electroconductivity were respectively attained. This ensured parametric values below standard limits for reuse of the regenerated effluent, e.g. in the olives washing machines, offering the possibility of closing the loop and thus rending the production process environmentally friendly.

Batch membrane treatment of olive vegetation wastewater from two-phase olive oil production process by threshold flux based methods

The more efficient continuous centrifugation-based olive oil extraction processes brought as drawback a significant increment of the generated effluents, highlighting olive vegetation wastewater (OVW) as the most polluted. In this work, OVW from a two-phase olive oil extraction process (OVW-2) was treated by means of batch membrane operations in sequence comprising UF, NF and RO. This treatment is capable of successfully removing the organic matter and other pollutants from the wastewater, but membrane fouling can limit drastically membranes operation and longevity. Threshold flux-based methods represent a reliable tool to avoid fouling problems and were formerly applied to treat OVW streams coming from a three-phase production line (OVW-3). Below threshold flux conditions, no relevant rates of fouling are observed, thus making the treatment process technically and economically feasible. In order to increase the threshold flux values, some pretreatment processes were conducted on the feedstock, such as pH-T flocculation and successively photocatalysis by novel lab-made titanium dioxide nanoparticles. The latter provided 22.3%, 17.6% and 20.4% further threshold flux increase to UF, NF and RO, respectively. At the end, a permeate with COD equal to 121mg/L was successfully obtained, respecting both Italian and Spanish standards for discharging purified OVW-2 in municipal sewers.

Assessment of olive mill solid residue (pomace) as an additive in lightweight brick production

The disposal of olive oil industrial waste is an environmental problem regardless of the manufacturing process. Contamination of soils with wet pomace (a waste product of the two-phase olive oil extraction method) can be a serious problem. Moreover, it cannot be composted or burned without expensive pre-treatment. In this work, we used wet pomace as a pore-forming additive in the manufacture of clay bricks to evaluate the possibility of obtaining a lightweight construction material with good insulating characteristics. To this end, bricks were prepared by adding 5, 10, 15, 20, and 25wt% wet pomace to the clay without additional water. The results indicate that the incorporation of 10wt% wet pomace is beneficial for manufacturing good-quality bricks, obtaining an apparent density of 1.43g/cm3, a compressive strength of 40.22MPa, and a thermal conductivity of 0.72W/mK.

Non-supplemented aqueous extract from dry olive mill residue: A possible medium for fungal manganese peroxidase production

The low moisture content of the dry olive mill residue (DOR), solid waste from the two-phase olive oil extraction process, enables its long-term storage and its ready reconstitution with water thus leading to a candidate liquid growth medium for the microbial production of enzymes of commercial interest. To test this hypothesis, two white-rot fungi (WRF), namely Lentinus tigrinus CBS 577.79 and Phlebia sp. DABAC 9, were grown in shaken cultures on non-supplemented aqueous extracts of the dry olive mill residue (ADOR) and compared for their ability to grow therein and produce Mn-dependent peroxidase (MnP). Then, in order to assess the feasibility of scale transfer to the reactor level, the two fungi were grown in a 3-L bubble-column reactor on 25% (w/v) ADOR at 28°C and an aeration rate of 0.3vvm. Under these conditions, L. tigrinus and Phlebia sp. produced 42.60±1.74 and 38.88±1.68 nkatal mL−1 MnP with respective mean volumetric productivities of 222.9 and 324.1nkatalL−1h−1. These results clearly show that the use of non-supplemented ADOR as a production medium enables a significant MnP production thus representing an excellent basis for process optimization.

Fired clay masonry units production incorporating two-phase olive mill waste (alperujo)

This work deals with the use of alperujo, the main residue from the two-phase olive oil extraction process, as a raw material in fired clay masonry units production. Different amounts (3, 6 and 12wt%) of clay were substituted by alperujo, and the properties of the resulting ceramic units were compared to those of conventional products. Results show that a number of advantages can be obtained. At 12wt% alperujo addition, masonry units present lower density (1710kgm−3 compared to 1850kgm−3 reference value) and higher thermal insulation effectiveness (18% reduction in the bulk of fired clay thermal conductivity). With respect to mechanical properties, the fired bending strength attained of approximately 14Nmm−2 is sufficiently high for this type of unit. In addition, the heating value obtained from the organic content of the added alperujo can cause a decrease in the heating requirements in the firing process.

Co-composting of olive husks with high moisture contents: Organic matter dynamics and compost quality

As the adoption of new generation, two-phase olive oil extraction systems becomes more widespread, there is an increasing need to evaluate the feasibility of co-composting processes to treat the resulting olive husk by-products that often present particularly elevated moisture contents with respect to traditional two-phase systems. The present work compares process parameters, organic matter dynamics and compost quality during the co-composting of two olive husks having different initial moisture contents, with the adoption of agricultural organic residues as bulking/absorbent agents and forced aeration. Despite the elevated moisture content, the co-composting conditions adopted were effective in reducing the elevated contents of water soluble organic matter, phenolic and lipidic compounds as well as reducing the extreme phytotoxicity of the experimental husk. Organic matter evolution during composting showed that the stabilization process in the two husks was comparable, and final compost quality was adequate in both cases.

Bioactive Compounds with Added Value Prepared from Terpenes Contained in Solid Wastes from the Olive Oil Industry

Starting from solid wastes from two-phase olive-oil extraction, the pentacyclic triterpenes oleanolic acid and maslinic acid were isolated. These natural compounds were transformed into methyl olean-12-en-28-oate (5), which then was transformed into several seco-C-ring triterpene compounds by chemical and photolytic modifications. The triene seco-products were fragmented through several oxidative procedures to produce, simultaneously, cis- and trans-decalin derivatives, both potential synthons for bioactive compounds. The chemical behavior of the isolated fragments was investigated, and a suitable approach to several low-molecular-weight terpenes was performed. These are interesting processes for the value-addition to solid waste from the olive-oil industry.

Valorisation of wastewater from two-phase olive oil extraction in fired clay brick production

Wastewater issued from oil-washing stage (OWW) in the two-phase olive oil extraction method was used to replace fresh water in clay brick manufacture. The extrusion trials were performed with one of the ceramic bodies currently being used in a local brick factory for red facing bricks (RB) production. Fresh water or OWW was added to a final consistency of 2.4 kg/cm 2, the same value as used at industrial scale for this kind of clay mixture. Comparative results of technological properties of facing bricks are presented. Results show that the products obtained with olive oil wastewater are comparable to traditional ones in terms of extrusion performance and technological properties of end products. Even dry-bending strength of the body formed by wastewater improves by 33% compared to fresh water body. In addition, heating requirements can be reduced in the range 2.4–7.3% depending on the final product. This application can alleviate environmental impacts from the olive oil extraction industry and, at the same time, result in economic savings for the brick manufacturing industry.

Isolation of a powerful antioxidant from Olea europaea fruit-mill waste: 3,4-Dihydroxyphenylglycol

Nutritional and antioxidant properties of phenolic compounds are important in relation to human health and palatability of products. 3,4-Dihydroxyphenylglycol (DHPG) is a strong antioxidant found in small amounts in virgin olive oil and table olives, with an antioxidant activity even higher than that of the powerful hydroxytyrosol. The origin of this antioxidant is completely unclear since has never been reported as a free plant metabolite. In this respect possible precursors of DHPG have also been discussed in this study. The presence of soluble compounds that either contain DHPG in their molecular structure or act as substrates for its synthesis has been showed for the first time. The quantities of DHPG recovered in olive drupe tissue by thermal treatment exceed widely the values indicated in the literature, showing the release or formation of additional DHPG from precursors after heating. In addition, DHPG obtained under certain extraction conditions from fresh solid waste of two-phase olive oil extraction systems (alperujo) is its most important phenolic compound. Therefore, the solid olive waste is a good source of this simple monomer phenol. The chemical structure, purity and racemic nature of isolated DHPG were also analysed for the first time by NMR experiments.