Solid state fermentation of waste pomace from olive processing

Typical samples of the solid waste (50% moisture) from olive oil processing were subjected, after an alkaline pretreatment, to delignification by Phanerochaete chryosporium, Phlebia radiata, Pleurotus ostreatus or Dacrymyces stellatus. The fermented material was then saccharified by Trichoderma spp to provide a substrate for the yeasts, Candida utilis or Saccharomyces cerevisiae. Success was judged by the level of crude protein generated, and a combination fermentation involving Phan chryosporium, T reesei and S cerevisiae increased the level of crude protein from 5.9% in the raw pomace to 40.3% in the fermented material. It is suggested that this solid‐state fermentation process could be used to manufacture an animal feed for the poultry industry in Jordan. © 1999 Society of Chemical Industry     

Study of the acid pretreatment and biodiesel production from olive pomace oil

The objective of this work was to study the two‐step acid base homogenous catalyzed transesterification of olive pomace oil, with the ultimate purpose of producing biodiesel under mild reaction conditions by optimizing the process. Optimization of the experimental procedure was conducted by a factorial design of 2³ under the acidic pretreatment step and during the basic transesterification. The optimal production of methyl esters (97.8%) was achieved for the experimental conditions H₂SO₄ = 20 wt%/CH₃OH = 35:1/T = 40^°C and KOH = 0.6+ fatty acid value /CH₃OH = 9:1/ T = 60^°C, in the acidic and basic stage of the process, respectively. Finally, to properly assess the quality of the biofuel produced, it was tested for all the European Standard properties.     

Stability of refined olive oil and olive‐pomace oil added by phenolic compounds from olive leaves

Refined olive oil and olive‐pomace oil were enriched with olive leaf phenolic compounds in order to enhance its quality and bring it closer to virgin olive oil. The changes that occurred in the concentrations of pure oleuropein, oleuropein aglycone, hydroxytyrosol acetyl and α‐tocopherol at 400 µg/kg of oil during the storage of refined olive oil and olive‐pomace oil under accelerated conditions (50 °C) were investigated. In a period of 4 months, α‐tocopherol decomposed by 75% whereas less than 40% of the phenols were lost. During storage, enzymatic olive leaf extract hydrolysate that contains two major compounds, hydroxytyrosol and oleuropein aglycone showed the highest antioxidant activity and the lowest detected stability, followed by oleuropein. The oleuropein in olive leaf extracts exhibited similar degradation profiles, reducing by 60–50% and 80% for the olive oil and olive‐pomace oil in 6 months, respectively. The acetylated extract, however, displayed a loss of 10 and 5% in olive oil and olive‐pomace oil, respectively. In the fatty acid composition, an increase in oleic acid and a decrease in linoleic acid were observed. The antiradical activities of the olive oil and olive‐pomace oil enriched with olive leaf phenolic compounds at 400 ppm showed that enzymatic hydrolysate extract had the highest protective effect against oil oxidation. Based on the Rancimat method, the oils with added leaf enzymatic hydrolysate extract had the lowest peroxide value and the highest stability. After 6 months of storage and at 120 °C, the oxidative resistance of refined olive oil and olive‐pomace oil reached 0.71 and 0.89 h, respectively, whereas that of the non‐enriched samples fell to zero.     

Comparison of near-infrared, fourier transform-infrared, and fourier transform-raman methods for determining olive pomace oil adulteration in extra virgin olive oil

The adulteration of extra virgin olive oil with cheaper oils is a major problem in the olive oil market. In this study, near-infrared, mid-infrared, and Raman spectroscopic techniques were used to quantify the amount of olive pomace oil adulteration in extra virgin olive oil. The concentration of olive pomace oil in extra virgin olive oil was in the range between 0 and 100% in 5% increments by weight. Of the methods studied, Fourier transform-Raman spectroscopy gave the highest correlation with a correlation coefficient of 0.997 and a standard error of prediction of 1.72%. The spectroscopic techniques have the potential to become a tool for rapid determination of adulteration in extra virgin olive oil, because they are casy to use and cost-effective.     

Photometric assay for polyphenol oxidase activity in olives, olive pastes, and virgin olive oils

A photometric method is proposed that allows the determination of phenolase activity in olive fruits, olive pastes, and virgin olive oil. The method can also be used to quantify partially purified phenolase from olives, and is based on the coupling between 4-methyl-o-benzoquinone, the reaction product of phenolase toward its substrate 4-methylcatechol, and the aromatic amine 4-amino-N,N-diethylaniline. The deep-blue adduct arising from this reaction has been characterized by means of nuclear magnetic resonance and mass spectrometric techniques and identified as 4-(4′-diethylaminophenylimino)-2-hydroxy-5-methyl-cyclohexa-2,5-dienone. This compound shows an absorption band, centered (in dichloromethane) at 617 nm, with an ε of 11,080 M⁻¹cm⁻¹. The main advantage of the proposed method resides in the high absorption coefficient of the adduct and its ultraviolet/visible absorption pattern, with a λ_max in a spectral region void of significant interferences by the pigments that ultimately will probably be present in the extracts to be tested by this proposed method. The method has proven to be sensitive, specific, and reliable. This paper is dedicated to the memory of Professor Francesco Corongiu, Dean of the Faculty of Sciences, University of Cagliari, prematurely deceased one year ago.     

Evaluation of virgin olive oil bitterness by total phenol content analysis

Bitterness is an important sensory attribute of virgin olive oil (VOO). It is usually assessed by tasting, which is a time‐consuming method and needs trained tasters. Bitterness is related to the phenolic compounds and can be estimated by the measurement of the specific absorbance at 225 nm (K₂₂₅). This paper proposes to evaluate oil bitterness intensity as estimated from the K₂₂₅ values measuring the phenol content. A significant relationship between phenol content and K₂₂₅ as well as a prediction model for bitterness intensity estimation from the phenol content was obtained. Classification of oil bitterness was based on the phenol content. Furthermore, when 12 VOO samples were classified by their bitterness intensities as estimated by the prediction model and by sensory analysis, more than 92% of the oil samples were correctly classified. Therefore, by measuring the phenol content, the bitterness intensity can be estimated and oils can be classified by their bitterness. This model may represent an easy method to evaluate the bitterness intensity without any sensory assessment.     

A multi-functional Ru Mo bimetallic catalyst for ultra-efficient C3 alcohols production from liquid phase hydrogenolysis of glycerol

Ru and Mo bimetallic catalysts supported on active carbon modified by phosphotungstic acid (PW) were designed and applied in glycerol hydrogenolysis reaction. The physicochemical properties of the catalysts were characterized and the presence of active sites was investigated from the perspective of the glycerol hydrogenolysis performance. The MoO_x is highly selective for the C—O bond cleavage of glycerol molecules, which can reasonably regulate the strong C—C bond cleavage activity of Ru nanoparticles. By using sequential deposition of Ru and Mo supported on mesoporous PW-C, the characterization results show that the combination of isolated low-valence MoO_x with metal Ru particles can form “MoO_x-Ru-PW”, which provides highly catalytic activity toward C—O bond cleavage, selectively producing more C3 alcohols (mainly 1,2(3)-propanediol). The glycerol conversion of 1% Mo/Ru/PW-C catalyst was 59.6%, the selectivity of C3 alcohol was 96.1%, and the selectivity of propanediol (1,2(3)-propanediol) was 94.9%. It is noteworthy that the selectivity of 1,3-propanediol reached 20.7% when the PW was 21.07% (mass). This study provides experimental evidence for the tandem dehydration and hydrogenation mechanism of the multifunctional Mo/Ru/PW-C catalyst.     

Malaxing temperature affects volatile and phenol composition as well as other analytical features of virgin olive oil

Three Italian olive varieties (Caroleo, Leccino and Dritta) were processed by centrifugation in the oil mill. The olive paste was kneaded at 20, 25, 30 and 35 °C. The results achieved revealed that the oil content in green volatiles from lipoxygenase pathway (including C₅ and C₆ compounds and especially unsaturated C₆ aldehydes) decreased progressively as the kneading temperature increased, dropping markedly at 35 °C. The content of phenols, o‐diphenols and secoiridoids showed an opposite trend, but the temperature of 35 °C was critical also for them, as it was for the majority of the other components, analytical parameters and indices related to quality, typicality and genuineness. In general, an increasing kneading temperatures increased the release of oil constituents from the vegetable tissue. This factor also affected the oil extraction yields. The best overall results were achieved by malaxing the olive paste at 30 °C. In fact, this temperature level led to achieving both pleasant green virgin olive oils and satisfactory oil extraction outputs.     

Enrichment of pomace olive oil in triterpenic acids during storage of “Alpeorujo” olive paste

Triterpenic acids are natural compounds present in plants and foods with beneficial properties for human health and thus they are desirable in the food, cosmetics and pharmaceutical industries. Pomace olive is considered a good source of these substances. In this study, oleanolic and maslinic acids were found to be the main triterpenic acids identified in pomace olive oil obtained from stored “Alpeorujo”. Determination of the two acids was achieved by a new procedure that consists of extracting the acids from the oil with a mixture of methanol/ethanol, and then separating and quantifying them by HPLC. Results showed that their concentration increased up to 16 g/kg of oil during storage of the pomace in large ponds for 7 months. The concentration of both triterpenic acids was similar in the pomace olive oil obtained by using the centrifugation system. By contrast, a much lower concentration of maslinic than oleanolic acid was detected in pomace olive oils obtained by solvent extraction from the previously centrifugated “Alpeorujo” paste. These triterpenic acids also contributed to the acidity of the crude oil. Likewise, the oil of the pomace paste was enriched in other substances such as 4‐ethylphenol and aliphatic alcohols during the storage of the paste in large ponds. Consequently, crude pomace olive oil can be considered a good source of triterpenic acids when obtained from a stored olive paste.     

Chemical structure of long-chain esters from “sansa” olive oil

The major objective of this study was to determine the chemical structure of long-chain esters present in lower-grade olive oil. The classes of esters composing the hexanediethyl ether (99∶1) extract of the wax fraction from a pomace olive oil were: (i) esters of oleic acid with C₁−C₆ alcohols, (ii) esters of oleic acid with long-chain aliphatic alcohols in the range C₂₂−C₂₈ and (iii) benzyl alcohol esters of the very long-chain saturated fatty acids C₂₆ and C₂₈. The analysis and the structure assignments were carried out by gas chromatography coupled with mass spectrometry and by comparison with synthetic authentic model compounds. This work provided precise data on the chemical nature of the wax esters present in olive oil and should represent a means to detect adulteration of higher-grade olive oil with less expensive pomace olive oil and seed oils.     

Elimination of polycyclic aromatic hydrocarbons by bleaching of olive pomace oil

A detailed study of the efficacy of the bleaching process for elimination of polycyclic aromatic hydrocarbons in Spanish olive pomace oils has been carried out. For this purpose active carbon with bleaching earth was used as absorbent. The amount of benzo‐(α)‐pyrene was determined by reversed‐phase high‐performance liquid chromatography with a Fluorimetric detector. The use of exhausted filter‐cakes in countercurrent processes with a cake formed of active carbon and bleaching earth is very efficient for reducing the initial content of benzo‐(α)‐pyrene before the addition of fresh adsorbent, thus reducing the amounts of carbon and earth required.     

The hydrocarbon fraction of virgin olive oil and changes resulting from refining

In numerous Spanish virgin olive oils, 6,10-dimethyl-1-undecene, various sesquiterpenes, the series ofn-alkanes from C14 to C35, n-8-heptadecene and squalene are the only less volatile components detected by gas chromatography in the hydrocarbon fraction. In oils from olives of the Arbequine variety, a series ofn-9-alkenes has also been found. In refined oils, notable features are the absence of the most volatile compounds and the appearance of other hydrocarbons produced during the refining process. Among these,n-alkanes, alkadienes (mainlyn-hexacosadiene), stigmasta-3,5-diene, isomerization products of squalene, isoprenoidal polyolefins coming from hydroxy derivatives of squalene and steroidal hydrocarbons derived from 24-methylene cycloartanol were identified. Physical refining produces larger amounts of degradation products and greater losses ofn-alkanes than chemical processing. Squalene is the major hydrocarbon component in all oils, both virgin and refined. The ranges of concentration for the different hydrocarbons found in Spanish virgin olive oils are presented.     

The volatile composition of samples from the blend of monovarietal olive oils and from the processing of mixtures of olive fruits

The volatile fraction deriving from the lipoxygenase pathway of samples obtained by processing olive fruits of 2 cultivars in known proportions was compared with that of samples deriving from the blending of oils extracted from the same cultivars and in the same proportions. The varieties considered for the mixtures were Coratina and Koroneiki, Coratina and Frantoio, and Dritta and Bosana, respectively. The results confirmed that the accumulation of each volatile compound from the lipoxygenase pathway in the monovarietal oils was different and closely dependent on the genetic store of each variety. The concentrations of the mentioned compounds appeared to change in a way proportional to the percent of each monovarietal oil in the samples obtained by blending 2 monovarietal oils. Instead, the oils obtained by processing mixtures of fruits from the 2 corresponding cultivars showed a striking accumulation of volatile compounds, especially of C₆‐compounds, which reached higher concentration at different percentages depending on the cultivars processed.     

Potential of selected Portuguese cultivars for the production of high quality monovarietal virgin olive oil

The effect of cultivar and ripeness stage on the potential nutritional value of monovarietal extra virgin olive oils (MEVOOs) obtained from Cordovil, Carrasquinha, Verdeal, and Negrinha do Freixo cultivars was investigated. MEVOOs produced were characterized by high oleic acid (72–83%), tocopherol (182–530 mg/kg), and phenolic compounds (326–1110 mg/kg) content and by a similar polyphenolic profile. 1‐Penten‐3‐one was found to be the compound with the highest contribution for the aroma of the four MEVOO, related to bitter, pungent, and leaf attributes. MEVOO from Verdeal cultivar showed the best performance in terms of the composition: the highest yield of oil, the highest content of oleic acid, high tocopherol, polyphenol and sterol content, and the lowest content of linoleic acid. These characteristics give to these MEVOO not only a great oxidative stability but also interesting properties from the health point of view. MEVOO obtained with fruits at the maturity index of around 4 were in general richer in beneficial minor compounds. MEVOO produced were discriminated by variety and ripeness stage, using a stepwise linear discriminant analysis. This discrimination will in the future enable the prevention of adulteration of these monovarietal olive oils with specific nutritional composition with other olive oils. Practical implications: High‐quality MEVOOs have recently been introduced in the market, which for growers is a practical way to differentiate and increase the commercial value of extra virgin olive oil. The quantification of major and minor olive oil compounds in monovarietal olive oils represents an objective way of predicting the sensory characteristics, stability, and potential health benefits of the oils, as well as preventing their adulteration with other olive oils. This study will help in the selection of olive varieties during the maintenance or development of new olive orchards and also to select optimum harvest period for these varieties, in order to obtain MEVOOs with the maximum quality and health benefits for consumers.     

Improvement of fluidized‐bed dryers for drying solid waste (olive pomace) in olive oil mills

Olive pomace from the two‐phase method of olive oil extraction (two‐phase olive pomace) must be dried from about 65% [wet basis (wb)] to about 8%, in order to extract part of the remaining pomace oil (about 3 wb‐%). An innovative dryer based on a fluidized bed is developed in this study. The objective is to improve olive pomace drying with low energy cost and high product quality by using optimal operating conditions, e.g. temperature and air flow rate, feeding solid moisture, and a control system. The bed operating temperature was set at 125 °C to obtain a good olive pomace oil quality and to reduce the thermal power consumption and drying time. The dried material is rather homogeneous and contains a negligible amount of polycyclic aromatic hydrocarbons. The fluidized bed was further improved with a moving bed joined by a conical device to the fluidized‐bed freeboard. This is a powerful combination in which the moving bed acts as a pre‐dryer of the wet solid and also as a filter of the output gas, with more than 99.9% of fines retention. The mean power consumption of the improved fluidized‐moving‐bed plant is 1 kWh/kg_water; this means a significant reduction of power cost with respect to the rotary dryers, which require about 1.4 kWh/kg_water.     

Stabilization of refined olive oil by enrichment with chlorophyll pigments extracted from Chemlali olive leaves

This paper presents the first investigation on the effect of enrichment refined olive oil by chlorophyll pigment extracted from Chemlali olive leaves during storage (6 months). The changes that occurred in the quality indices, fatty acids, sterol, and phenolic content were investigated during the storage of refined olive oil under RT (20°C) and accelerated conditions (50°C) in the dark. Additionally, the pigments (chlorophyll and carotene) changes during 6 months of oil storage were evaluated. At the end of the storage, more than 90% of chlorophyll pigments decomposed in all samples, while, carotene pigment loss was lower showing up to 60 and 85% loss for oil stored at 20 and 50°C, respectively, at the end of storage. The reduction of total phenolic compounds exhibited similar degradation profiles, being reduced by 5% and up to 60% for the enriched refined olive oil stored at 20 and 50°C in 6 months, respectively. In the fatty acid composition, an increase in oleic acid and a decrease in linoleic and linolenic acids were less significant in enriched than non‐enriched refined olive oil. On the other hand, sterol composition was less affected by storage in enriched oil samples. However, the sterol concentration of the oil samples showed an increase in β‐sitosterol, 24‐methylene cholesterol, stigmasterol, and a decrease in cholesterol, Δ5, 24‐stigmastadienol percentage at the end of storage. Based on the Rancimat method, the oils with added leaf pigment extract had the lowest peroxide value and the highest stability. After 6 months of storage, the oxidative resistance of refined olive oil fell to 0.2 and to zero for enriched refined olive oil stored at 20 and 50°C, respectively.     

Kinetics of the degradation by catalytic hydrogenation of tyrosol,a model molecule present in olive oil waste waters

Olive mill wastewaters (OMW) constitute an important environmental problem due, among other things, to their high phenolic content. The phytotoxicity of polyphenols makes them resistant to biological treatment. A three‐step process comprising adsorption–concentration, catalytic hydrogenation and regeneration on a fixed bed of adsorbent–catalyst was investigated to remove such compounds. Tyrosol (2‐(4‐hydroxyphenyl)‐ethanol) was taken as representative of the polyphenols present in OMW. The catalytic hydrogenation of tyrosol by 30 g kg^?1 ruthenium/activated carbon catalyst was carried out in order to establish the reaction mechanism and kinetics necessary for the design of a pilot‐scale reactor. Total conversion of tyrosol into non‐aromatic compounds was achieved under mild conditions of temperature and pressure. The overall rate of tyrosol removal at 4 MPa and 353 K was . Copyright © 2003 Society of Chemical Industry