Olive Oil Extraction Process Research Articles

Effects of long-term olive mill wastewater spreading on the physiological and biochemical responses of adult Chemlali olive trees (Olea europaea L.)

Olive mill wastewater (OMW), a by-product from the olive oil extraction process, is annually produced in huge amounts in olive-growing areas and represents a significant environmental problem in Mediterranean areas. Whereas its high organic load and polyphenols concentrations are associated with troublesome environmental effects, its rich mineral and organic matter contents represent valuable nutrients. This study aimed to investigate adult ‘Chemlali’ olive trees subjected to OMW application at three doses (50, 100, and 200m3ha−1year−1) after eight successive years in an olive field. The main focus of the study was on gas exchange characteristics, photosynthetic pigments, soluble sugars, total phenolic compounds, antioxidant activity, leaf mineral nutrient and yield of the trees. The findings showed significant raises of net photosynthesis (Pn) and stomatal conductance (Gs) in OMW treated olive trees by 50 and 100m3ha−1. The lowest Pn and Gs rates were recorded in treatment with the highest OMW dose (200m3ha−1). In addition, olive trees amended with 200m3ha−1 exhibited a significant decrease of both chlorophyll (a+b) and carotenoid contents, while olive plants which received 50 and 100m3ha−1 of OMW showed higher photosynthetic pigments contents compared to the control olive trees. However, there was no significant difference in carotenoid content. Soluble sugars, total phenol contents and antioxidant activity increment were noticed in leaf plants amended with a 200m3ha−1 dose. The OMW spreading rates at 50 and 100m3ha−1 significantly increased the mineral contents of leaves (N, P, K, Ca and Mg). Nevertheless, the highest OMW application was associated with a significant reduction of olive leaf nutrient concentrations. Olive yield showed a continuous improvement of up to 100m3ha−1year−1 spread rate. The present study confirms that olive trees responses were dependent on OMW dose applied. Consequently, key physiological parameters of adult olive trees seemed to benefit from spreading OMW at moderate doses (50 and 100m3ha−1year−1) while the application of a higher dose (200m3ha−1year−1) seemed to disrupt them.

Shelf-life evaluation of virgin olive oil extracted from olives subjected to nonthermal pretreatments for yield increase

Abstract Critical process parameters for the yield and quality of olive oils are the temperature and treatment duration of the malaxation process. A balance between oil yield and quality must be achieved. Novel technologies such as High Pressure (HP) and Pulsed Electric Fields (PEF) that cause alterations to cell permeability, may promote the olive oil extraction process during malaxation, resulting in higher oil yields. Three different varieties of Olive fruits (Tsounati, Amfissis and Manaki var.) were subjected to different HP (200 and 600 MPa, 25 °C for 1 and 5 min) and PEF (1.6–70.0 kJ/kg) process conditions before malaxation (30 min at 30 °C). The extraction yield was increased up to 18 and 16% for PEF and HP treated olive fruits, respectively. The shelf-life tests indicate that the oil quality from nonthermally pretreated olives is dependent on the technology and process conditions used. An increase of oil oxidative stability for PEF and HP treated olives was shown, compared to control samples. The results show that HP and PEF could be applied for the production of superior quality virgin olive oil with increased yield.

Destinação e reaproveitamento de subprodutos da extração olivícola

The waste obtained from olive oil extraction process are by products generated in different ways and composition, according to the used extraction equipment, the olive variety and the fruit maturity. In the olives pressing traditional process, using continuous three-phase process, the waste produced comprise the liquid portion (vegetation water) + solid portion (solid waste). The olive solid portion to suffer new extraction produces the oil residue, while the aqueous residue is usually discarded without control, causing various environmental problems. When using a two-phase system for oil production, the problem is eliminated, resulting in a new waste, known as ‘alperujo’ and water vegetation. The industries of olive extraction are trying to invest in alternatives that enable the use of their waste as fertilizer, herbicide, animal feed and residual oil. Therefore, studies in this area are needed in order to generate new alternatives for the reuse of extractive industry waste, contributing to the sustainability and reducing environmental impact.

Destinação e Reaproveitamento de Subprodutos da Extração Olivícola

The waste obtained from olive oil extraction process are by products generated in different ways and composition, according to the used extraction equipment, the olive variety and the fruit maturity. In the olives pressing traditional process, using continuous three-phase process, the waste produced comprise the liquid portion (vegetation water) + solid portion (solid waste). The olive solid portion to suffer new extraction produces the oil residue, while the aqueous residue is usually discarded without control, causing various environmental problems. When using a two-phase system for oil production, the problem is eliminated, resulting in a new waste, known as ‘alperujo’ and water vegetation. The industries of olive extraction are trying to invest in alternatives that enable the use of their waste as fertilizer, herbicide, animal feed and residual oil. Therefore, studies in this area are needed in order to generate new alternatives for the reuse of extractive industry waste, contributing to the sustainability and reducing environmental impact.

Enumeration and rapid identification of yeasts during extraction processes of extra virgin olive oil in Tuscany.

The aim of this study was to evaluate the occurrence of yeast populations during different olive oil extraction processes, carried out in three consecutive years in Tuscany (Italy), by analysing crushed pastes, kneaded pastes, oil from decanter and pomaces. The results showed yeast concentrations ranging between 10(3) and 10(5)CFU/g or per mL. Seventeen dominant yeast species were identified by random amplified polymorphic DNA with primer M13 and their identification was confirmed by restriction fragments length polymorphism of ribosomal internal transcribed spacer and sequencing rRNA genes. The isolation frequencies of each species in the collected samples pointed out that the occurrence of the various yeast species in olive oil extraction process was dependent not only on the yeasts contaminating the olives but also on the yeasts colonizing the plant for oil extraction. In fact, eleven dominant yeast species were detected from the washed olives, but only three of them were also found in oil samples at significant isolation frequency. On the contrary, the most abundant species in oil samples, Yamadazyma terventina, did not occur in washed olive samples. These findings suggest a phenomenon of contamination of the plant for oil extraction that selects some yeast species that could affect the quality of olive oil.

Treated Olive Mill Wastewater Effects on Soil Properties and Plant Growth

Olive-oil production has a vital impact on the socioeconomic development in most Mediterranean countries, where 97.5 % of the world oil is produced. However, the olive-oil extraction process generates considerable quantities of an agro-industrial effluent, olive mill wastewater (OMW), which has negative impact on the environment and biological life. The objective of this study was to evaluate the potential use of OMW treated by different technologies in irrigation and determine its effect on the plant growth and soil quality parameters. Different technologies were used to treat the OMW, the resultant treated OMW was used to irrigate the maize planted in the pot experiment. The results indicated that UOMW increased soil salinity and reduced plant growth, while the treated OMW by different technologies improved plant growth and resulted in lower soil pH. The impact on other soil properties varied depending on the techniques used for treatments. Although treated OMW enhanced plant growth compared with the untreated, the plant growth remained lower than that obtained using the potable water with fertilizers, indicating lack of some essential plant nutrients.

Agronomic and economic implications of using treated olive mill wastewater in maize production

Olive mill wastewater (OMWW) is a byproduct of the olive oil extraction process, characterized by high polluting load and polyphenols content. The treatment of OMWW, using microfiltration and XAD4 resin, results in recovery of polyphenols, and also in an effluent (treated OMWW) with decreased organic load and phytotoxic properties, compared to the initial OMWW. The effects of the treated OMWW (T-OMWW) application on maize kernel yield and quality, and soil quality were investigated through a two-year field experiment. T-OMWW was applied by drip irrigation to maize cultivation using two rates of 25–50 t ha−1 year−1, with the addition of mineral fertilization. Furthermore, a treatment of only T-OMWW applied at the rate of 50 t ha−1 year−1 and an only mineral fertilization treatment were used. Maize kernel yield and quality were not significantly different between mineral fertilization and T-OMWW application, hence indicating that T-OMWW could fully substitute mineral fertilization under the conditions of our study. Based on the experimental results, an economic analysis was undertaken in order to evaluate the economic implications of T-OMWW application by drip irrigation to maize production. Three scenarios were investigated: (a) mineral fertilization only, (b) T-OMWW application at the rate of 50 t ha−1 year−1 only, and (c) T-OMWW application at the rate of 25 t ha−1 year−1 combined with reduced mineral fertilization. The cost analysis showed that T-OMWW application at the rate of 50 t ha−1 year−1 was the least expensive of the three scenarios investigated, irrespective of the distance between the olive mill and the farm. The use of the farm tractor and tanker for the T-OMWW transportation was more cost effective than hiring a liquid transport company, for distance up to approximately 20 km. For greater distance, hiring a liquid transport company was more economical.

Two‐phase olive mill waste (alpeorujo) as carbon source for biosurfactant production

AbstractBACKGROUNDThe olive oil extraction process currently used in Spain and other Mediterranean countries generates large amounts of a semi‐solid by‐product known as ‘alpeorujo’ or ‘two‐phase olive mill waste’ (TPOMW). Although TPOMW can be a source of valuable compounds, it is mostly dried and burnt to produce energy. This paper, and for the first time, reports the use of TPOMW as the main carbon source for the production of surfactin, a high added value biosurfactant, by Bacillus subtilis DSM 3256.RESULTSBacillus subtilis DSM 3256 was able to grow on TPOMW, the surface tension of the culture medium being reduced to 30.1 ± 0.9 mN m−1. FTIR and mass spectrometry determinations confirmed that the biosurfactant produced was surfactin. The highest surfactin concentration was obtained after 36 h fermentation, and the product yield from biomass (YP/X) was 0.068 g g−1. Part of the phenolic compounds of TPOMW was extracted with the biosurfactant.CONCLUSIONTwo‐phase olive mill waste can be used as the main carbon source for the production of surfactin. Surfactin yield from biomass was similar to that achieved with other bacterial strains and carbon sources. The biosurfactant was successfully applied to the remediation of sandy soils contaminated with engine oil. © 2015 Society of Chemical Industry

Structural Characterization and Biological Activities of Polysaccharides from Olive Mill Wastewater.

Olive mill wastewater (OMWW), the main waste product of olive oil extraction process, was investigated as a source of polysaccharides. The yield of alcohol insoluble residue (AIR) was 20.5 % based on the dry matter of OMWW. Extraction with water gave water soluble (WSF) and insoluble (WIF) fractions from AIR with yields of 13.3 % (w/w) and 3.7 % (w/w) based on the dry matter, respectively. Chemical composition and monosaccharide analysis indicated that glucose was the main monosaccharide of these extracts in addition to galactose, arabinose, rhamnose, and galacturonic acid. Prebiotic and antioxidant activities of polysaccharidic fractions from OMWW were evaluated. Results gave evidence for their scavenging capacity toward the 2,2'-diphenyl-1-picrylhydrazyle (DPPH) (IC50 value of 89.43 μg/mL) and hydroxyl radicals (IC50 value of 158.70 μg/mL), resistance toward artificial human gastric juice, and ability to be fermented by Lactobacilli strains.

Micronized natural talc with a low particle size and a high carbonate rate is more effective at breaking down oil‐in‐water emulsion

Micronized natural talc (MNT) has demonstrated to be very useful to break down emulsions formed during the virgin olive oil extraction process, improving the oil yield. This study was aimed to obtain more insights into the mechanisms of MNT to break down oil‐in‐water emulsions. For this purpose, laboratory scale experiments were performed in order to evaluate the effect of different pectin concentrations (0.5, 1, 1.5, and 2%), used as an emulsifier agent, on the behavior of an oil‐in‐water interface. Afterward, to evaluate the effect of MNT dosage as well as its physicochemical characteristics on breaking o‐reducing emulsions, four MNTs differing in their particle size (D50) and carbonate rate were assayed at doses ranging from 0 to 1%. Increasing pectin concentration gave a rise in the emulsifying activity (EA). The emulsifier effect of pectins was weakened by the addition of increasing MNT dose. MNT physicochemical characteristics markedly affected the breaking of oil‐in‐water emulsions. Nonetheless, its effect depends on the dose of MNT applied to the emulsion. The highest decrease in EA was observed for MNT with the lowest D50 (2.4 μm) and the highest carbonate rate (4%) at 0.5%. In general, MNT containing lower D50 and high rate of carbonate showed better capacity for breaking oil‐in‐water emulsion.Practical applications: So far as can be ascertained, no quantitative study has been made, in vitro, on the relative merits of MNT addition as a technological aid in breaking down oil‐in‐water emulsions. This study provides deeper insights into the clarification of the effect of pectins as emulsifier agents, on aqueous emulsions of Hojiblanca virgin olive oil and how the addition of different doses of MNT, with different physicochemical characteristics, carried out the breaking of the oil‐in‐water emulsions.Effect of micronized natural talc physicochemical characteristics and dosage on the break‐down of oil‐in‐water emulsion.

On-line system based on hyperspectral information to estimate acidity, moisture and peroxides in olive oil samples

The analysis of the quality of virgin olive oil involves the determination of a series of properties, such as chemical indexes and organoleptic characteristics. In addition, the determination of these properties in real-time could be useful in order to improve the olive oil extraction process since the process parameters could be regulated with the real-time moisture information.In this paper, the feasibility of using a non-invasive hyperspectral device, in order to determine on-line three parameters of the olive oil (free acidity, peroxide index and moisture) is studied. In order to study the correlation between these parameters and the information obtained by the hyperspectral sensor (absorption level), three different methods were applied: genetic algorithms (GA), least absolute shrinkage and selection operator (LASSO), and successive projection algorithm (SPA). From the experimental results, reduced values in cross validation were obtained and the optimal wavelengths were pointed out.

Investigation on microbiology of olive oil extraction process

Several batches of approx. 200 kg olives from Frantoio and Moraiolo cultivars were processed in an oil mill at two dates of harvesting. Samples were collected in several steps of extraction process for sensory, chemical and microbial analyses. All extracted olive oil from the second olive harvesting date was affected by sensory defects and hence classified as being “non-extra virgin”. A distinction between extra virgin olive oil and nonextra virgin olive oil obtained from both harvesting dates was explained by the volatile compounds content of olive oil samples and by yeast and mould counts collected at different processing steps.

Evaluation of phytotoxicity effect of olive mill wastewater treated by different technologies on seed germination of barley (Hordeum vulgare L.).

Olive-mill wastewater (OMW) is a by-product effluent of olive oil extraction process that is produced in large amount in the Mediterranean region. OMW is believed to induce phytotoxic effect on organisms including seed germination and plant growth. The objective of this study was to evaluate the impact of untreated and treated OMW with different techniques on seed germination of barley (Hordeum vulgare L.). The following treatments were investigated: (1) tap water (control); (2) OMW treated by aerobic biological technology in a Jacto Reactor (JR); (3) OMW treated by solar fenton oxidation (SFO); (4) OMW treated by microfiltration followed by nanofiltration (MF+NF); (5) OMW treated by microfiltration followed by reverse osmosis (MF+RO) process; (6) diluted OMW with tap water (25 % OMW); (7) diluted OMW with tap water (50 % OMW); (8) diluted OMW with tap water (75 % OMW); and (9) untreated OMW (100 % OMW). A germination test was conducted in an incubator at temperature of 23 (∘)C. In each petri dish, a filter paper was mounted and ten seeds of barley were placed on the filter paper. Five milliliter of water were added to each petri dish. The seed germination was determined by counting the number of germinated seeds to calculate the percentage of germination (G %). Germination rate index (GRI), seed vigor index (SVI), and phytotoxicity index (PI) were also calculated. Then, the dry weights and lengths of the shoots and the roots of the germinated seeds were measured. The results show that 100, 75, and 50 %OMW were very phytotoxic and completely prohibited seed germination. However, phytotoxicity decreased significantly following treatments of OMW with all techniques investigated and by the 25 % OMW dilution, as results of removing the phenols and other phytotoxic organic compounds from the OMW or by diluting it. This was evidenced by relative enhancement of the dry weights and lengths of shoot and root as well as the G %, GRI, SVG, and PI. It was concluded that if OMW will be used for irrigating crops, it has to be first treated or diluted with tap water at a ratio of 1:3 OMW:water at least. The most efficient treatment techniques in reducing the phytotoxicity of OMW were the MF+RO, followed by SFO and JR.

3D computational fluid dynamics simulation and experimental validation for prediction of heat transfer in a new malaxer machine

In the mechanical olive oil extraction process, heating is a common practice to promote the extraction of extra virgin olive oil, especially in a malaxer machine. Nevertheless, the process of heat transfer in the malaxer machine has not been fully explored. Temperature is a dominant factor in various physiochemical changes and in enzymatic reactions that occur during the malaxation process and a bad management of this parameter may affect the quality of the oil irreversibly. To establish a model of the temperature distribution of the whole malaxer machine, computational fluid dynamics (CFD) may be the most effective method. In this study, a mathematical model that analyses the fluid flow and heat transfer of an olive paste malaxing process was developed and solved using a finite element-based software (COMSOL Multiphysics). The objective is to study the olive paste behaviour in order to improve the design of a malaxer machine increasing the effect of the fluid flow on the heat transfer performance. The results of this paper show that particular design parameters influence the flow and temperature fields inside the malaxer machine. The validity of our mathematical model is corroborated by our experimental work on the olive paste heating in an experimental industrial malaxer prototype equipped with specifically designed kneading tools in an industrial continuous olive oil plant. Good agreement exists between the simulated and experimental results. The 3D CFD simulation model has been developed for two different geometry configurations of the machine. The temperature field and the trajectories of single particles determine an intermediate cold area that is wider in traditional malaxer machines (with a single set of blades) compared to the examined malaxer prototype (with a double set of blades). Additionally, a warm area close to the horizontal axis is shown to be smaller and characterised by higher temperatures. The presence of two sets of blades reduces the unevenness of the temperature field during olive paste kneading.

What’s now, what’s new and what’s next in virgin olive oil elaboration systems? A perspective on current knowledge and future trends

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.

Plant innovation in the olive oil extraction process: A comparison of efficiency and energy consumption between microwave treatment and traditional malaxation of olive pastes

In this study, we discuss the introduction of microwave radiation replacing the malaxation of olive paste and associated experimentation. A major limitation of olive oil extraction plants is the discontinuity in the extraction process due to the current technology used during the conditioning of the olive paste. In this work, a microwave-assisted system was developed and applied in an industrial-scale olive oil extraction plant to preliminarily analyse the installation and determine any advantages to improving the process continuity. The apparatus, which is specifically designed to be industrially implemented, was evaluated in terms of electrical and thermal energy consumption and the extraction yield of the olive oil. Special attention was given to a microstructural investigation of the olive paste using SEM analyses. The microwave treatment does not significantly influence the extraction yield compared with conventional malaxation, but the SEM results demonstrated that the microwave technique efficiently breaks down cell walls and membranes, thus increasing the release of oil. In addition, some benefits are observed that result from making the olive oil extraction process continuous. The results acquired from this study are promising for microwave implementation in olive oil extraction plants in the future.

Olive pomace extract (OPE) as corrosion inhibitor for steel in HCl medium

ObjectiveTo explore the possibility of reuse olive pomace extract as a corrosion inhibition of steel in an acidic medium (HCL, 1 mol/L), and to compare the inhibitory effect of olive pomace (OP) samples collected from three extraction process of olive oil: press process, continuous process three-phase and continuous process two-phase and olive pomace continuous process two-phase without stone and stone of olive (both fractions were separated by mill) in the eastern region of Morocco. MethodsThe electrochemical behavior of the C38 steel in HCl medium in the absence and presence olive pomace was studied by gravimetric and electrochemical techniques such as potentiodynamic polarization, linear polarization and impedance spectroscopy. The effect of temperature was also studied. The experimental data with several adsorption isotherms at different temperatures were tested to determine the standard free energy of adsorption process and the adsorption mode of inhibitor on the surface of the steel were studied. ResultsThe samples of the olive pomace tested in the corrosion experiment have a very complex and heterogeneous physicochemical composition. They contain a variety of organic and inorganic compounds of very different nature and concentration, allowing the olive pomace play a very important role in anti-corrosion activity. The inhibition efficiency increased with increased olive pomace concentration to attain a maximum value of 92.1% at 1.4×10−5 with small differences among the other samples of olive pomace. ConclusionsThe use of solid waste (pomace) of crushing olives (oil mills) as green inhibitors in the fight of corrosion plays a dual function, firstly, destituting the pollution of the receiving environments (soil, water, etc.) and on the other hand, a recovery of components (bioactive) such as phenolic compounds.

Replacement of the mixing fresh water by wastewater olive oil extraction in the extrusion of ceramic bricks

This investigation deals with the possibility of incorporating effluents resulting from olive oil extraction activity, as wastewater from olive-washing stage (OW) or wastewater from olive-oil washing stage (OOW), in the brick-making process. The feasibility of replacing mixing fresh water (FW) by OW or OOW of the extraction process of olive oil, in the process for manufacturing clay bricks, has been studied. FW, OW or OWW (22wt%) was added to the clay in order for it to acquire enough plasticity to the stage of molding by extrusion. Samples containing OW or OOW were found to be comparable in extrusion performance to a control product that used FW. Once extruded, test specimens were dried at 110°C (24h) and fired at 850 or 950°C (3°C/min) for 4h. The influence of replacing fresh water by wastes on the technological behavior of fired bricks was assessed by linear shrinkage, bulk density, water suction, water absorption and apparent porosity. Their mechanical and microstructural properties were also investigated by compressive strength and scanning electron microscopy (SEM), and thermal behavior by thermal conductivity. Results indicated that replacement of FW by OW or OOW produced slight improvements in the physical, mechanical and thermal properties of bricks. This may have been due to porosity generated by these wastes mainly closed pore type.Therefore, the use of these residues can alleviate the environmental impact generated by the industry of extraction of olive oil and, at the same time, represent an economic and water saving for the ceramic industry.

Specification and implementation of a continuous microwave-assisted system for paste malaxation in an olive oil extraction plant

An industrial prototype continuous microwave-assisted system (MWS) to condition olive paste was specified, built and implemented as an industrial process. The developed system was tested to assess its performance during implementation in an industrial olive oil extraction plant. The extraction efficiency of the olive oil plant was investigated for different operating conditions of the MWS and compared with conventional methods to condition the olive paste. The results indicate that exposing the olive paste to microwaves determines the thermal and non-thermal effects that influence the coalescence phenomena and the extraction efficiency. The experiments showed the feasibility of the continuous microwave-assisted prototype and great the potential to become an alternative technique to effectively condition olive paste. The MWS removes the limitations of the batch malaxation process and produces an olive oil extraction process that is truly continuous.

Low energy-demanding recovery of antioxidants and sugars from olive stones as preliminary steps in the biorefinery context

Olive stones constitute the main solid by-product of the olive oil extraction process. As a lignocellulosic material, their use as a source of fermentable sugars, antioxidants and other applications has been proposed. In this work the possibilities of a better use of this material through a relatively low energy-demanding operation, e.g. autoclave treatment, are assessed. Dilute acid extraction was used for evaluating the influence of the main variables (temperature, acid concentration and pretreatment time) on the sugar composition and the antioxidant capacity of liquid fractions (prehydrolyzates) issued from autoclave treatment. Results show that the highest production of fermentable sugars, 27g/100g initial dry matter, was obtained at the most severe pretreatment conditions (130°C for 90min and 2% sulfuric acid), with xylose being 90% of the released sugars, while cellulose degradation was limited. Concerning antioxidant capacity of the prehydrolyzates, the best result was obtained at the highest temperature (130°C) and time (90min) but using no acid. This procedure is proposed as a preliminary step of a broader treatment scheme which can also include further steps of pretreatment and eventually enzymatic hydrolysis and fermentation. As a conclusion, a two-step process strategy is suggested to optimize the recovery of antioxidants in the first step, and the production of fermentable sugars in the second step.