Acidification of Alperujo Paste Prevents Off-Odors During Their Storage in Open Air

Alperujo is the main paste produced by the olive oil industry that must be stored in big open air ponds for months before pomace olive oil is extracted. During this period, malodorous 4-ethylphenol is formed, and it represents a big environmental problem for the oil extracting factories. The aim of this investigation was to prevent the formation of this substance by acidification of the fresh paste. Several batches of fresh Alperujo were stored in 100-L plastic containers for 6 months without pH control and acidified up to pH 2 or 3. Acidification inhibited the formation of 4-ethylphenol as well as the growth of yeasts. By contrast, acidification of the paste did not affect oil acidity, triterpenic acid concentration, waxes or fatty acid composition. An increase in hydroxytyrosol of the aqueous phase of Alperujo was also observed because of hydroxytyrosol glucoside hydrolysis. The results indicated that acidification of Alperujo during storage under open air conditions reduced the formation of 4-ethylphenol, thereby diminishing the environmental impact of the pomace olive oil production.     

Fatty acid esters with short‐chain alcohols in two‐phase olive pomace oils

Two‐phase decanter olive pomace (TPOP) is the by‐product of a centrifugation system, used to produce olive oil, that separates olive oil and moist pomace. The water content in these olive pomaces is about 70%, while it was 45‐50% in the olive pomace stemming from three‐phase systems (oil, water, and pomace) and 30% in the old press system. The aim of this work is focused on quantification and changes undergone during olive pomace storage in ponds of esters of fatty acids with short‐chain linear alcohols, which can be considered as a refining loss. The results indicate that oil deterioration increases very rapidly, in particular when oil is extracted from the TPOP surface. Special attention should be paid to the storage of TPOP, establishing a maximum of 2 months in all cases.     

Formation of Triterpenoids throughout <Emphasis Type="Italic">Olea europaea</Emphasis> Fruit Ontogeny

Drupes were handpicked from olive (Olea europaea L.) trees, cv chemlali, at 13 distinct stages of fruit development, referred to as weeks after flowering (WAF), and analyzed for their free and esterified sterols and triterpenoids content. These two classes of compounds are synthesized via the acetate/mevalonate pathway and share common precursors up to oxidosqualene (OS). Cyclization of OS in either cycloartenol or beta-amyrin constitutes a branch point between primary (sterol pathway) and secondary (triterpenoid pathway) metabolisms. At the onset of fruit development, i.e., between 12 and 18 WAF, drupes were found to contain high amounts of alpha- and beta-amyrins as well as more-oxygenated compounds such as triterpenic diols (erythrodiol and uvaol) and acids (oleanolic, ursolic and maslinic acids). Concomitantly, sterol precursors were barely detectable. From 21 WAF, when the olive fruit reached its final size and began to turn from green to purple, alpha- and beta-amyrins were no longer present, while 4,4-dimethyl- and 4alpha-methylsterols started to be formed, indicating a redirection of the carbon flux from the triterpenoid pathway towards the sterol pathway. Between 21 and 30 WAF, sterol end products, mainly represented by sitosterol, progressively accumulated and triterpenic diols were replaced by triterpenic acids, essentially maslinic acid. Interestingly, the developing olive fruit was found to accumulate significant amounts of parkeol as an ester conjugate. Whatever the stage of development, triterpenoids represent the major triterpenic compounds of the olive fruit.     

Effect of irrigation applied to olive trees (Olea europaea L.) on phenolic compound transfer during olive oil extraction

The main objective of this research was to determine the extent to which irrigation practices affect the partitioning of phenolic compounds between olive paste, pomace, olive oil and wastewater. The current paper also aimed to study the effect of technological natural micro‐talc (NMT) addition during the oil extraction process on the partitioning of the phenolic compounds between solid and liquid phases. The results obtained in this study showed that irrigation applied to olive trees let to a considerable decrease in the phenol content of the olive paste. The water status of the trees affected the phenol synthesis in the olive fruit, and consequently the phenol content of the olive paste, more than the partitioning of the phenolic compounds during the olive oil extraction process. The most remarkable point of the phenol partitioning was related to the simple phenols. While in the samples from non‐irrigated trees the greater proportion of these phenols partitioned into the pomace, in samples from irrigated trees most of them were lost in the wastewater. After comparison of the results obtained from the experiments with and without NMT addition, it was concluded that the use of that co‐adjuvant did not significantly alter either the phenolic profile of the oil phase obtained or the content of the individual phenolic compounds.     

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.     

Supplementation of oils with oleanolic acid from the olive leaf (olea europaea)

A method was studied for utilization of olive leaf, which is a byproduct of olive tree pruning and olive oil production. Our strategy involves two stages. The first is a simple procedure for isolating oleanolic acid, a compound with known biological activity. The second stage involves supplementation of different types of oil with this triterpenic acid. Two protocols were used for incorporating this acid into oils, either as a solid or as a solution, at concentrations from 200 to 1000 ppm. Oleanolic acid in the prepared oils was quantified by gas liquid chromatography. At the concentrations analyzed, the oleanolic acid content measured in all oil samples was equal to the amount added (p <0.05). No significant difference was observed (p <0.05) between the two supplementation procedures in any of the oils.     

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.     

Natural antioxidants and volatile compounds of virgin olive oils obtained by two or three‐phases centrifugal decanters

Research has been carried out to ascertain the influence of different centrifugal decanters employed in olive process on oil yields and qualitative characteristics and composition of volatile compounds of virgin olive oil. Tests were performed in an olive oil mill equipped with centrifugal decanters at two or three‐phases. Results show that oil yields were similar and oils extracted from good‐quality olives do not differ in free fatty acids, peroxide value, UV absorptions and organoleptic assessment. Total phenols and o‐diphenols content as well as induction time values are higher in oils obtained by the centrifugal decanter at two‐phases, because it requires less quantity of water added to olive paste in comparison to the three‐phases centrifugal decanter. The amount of water added determines the dilution of the aqueous phase and lowers the concentration of the phenolic substances more soluble in vegetable waste water. Due to the partition equilibrium law the concentration of the same substances consequently diminishes in the oil. In this research, the coefficient of the partition equilibrium of total phenols between oil and vegetable water has been calculated and discussed. No significant difference occurred, due to the different decanters employed, in the average values of the volatile components of the head‐space of oils.     

Pentacyclic triterpenic acids from Argania spinosa

This work reports for the first time the presence of pentacyclic triterpenic acids in Argania spinosa. By solid/liquid extraction with absolute ethanol and GC‐FID analysis, we report that ursolic acid is the major triterpene in the leaf and fruit of argan (0.10–0.44% DW), followed by significant amounts of oleanolic acid (0.05–0.19% DW). Their contents in the leaf were four times higher than in the fruit. Minor levels of betulinic and maslinic acids were also determined in the fruit pulp. Our results suggest that the developmental stage of the plant organ and the environmental conditions modulate the biosynthesis of triterpenic acids in argan. Advanced stages of ontogeny and severe climatic conditions induced a selective production of lupenyl and ursanyl structures. Argan fruits and leaves constitute interesting raw materials for the obtaining of ursolic and oleanolic acids that are strongly demanded by the functional food and pharmaceutical industries. The utilization of dry pulp of argan fruits, a by‐product of the argan oil industry, for the obtaining of new triterpene‐based formulations of high added value would increase the profitability of these crops and might help to guarantee the survival of the A. spinosa forests in the long term. Practical applications: Argan fruits and leaves constitute interesting raw materials for obtaining ursolic and oleanolic acids. Morocco accumulates every year more than 44 500 tons of dry fruit pulp as a by‐product of the argan oil industry. The utilization of this biomass for the obtaining of bioactive compounds of high added value that could be used in the design of new functional food and drugs would help to increase the profitability of the argan crops and represent an intelligent manner of contributing to the A. spinosa survival.     

Quality characteristics of olive leaf‐olive oil preparations

Olive leaf‐olive oil preparations were obtained by vigorous mixing at various levels of addition (5, 10, 15%w/w) of new or mature leaves. After removal of the plant material via centrifugation, quality and sensory characteristics of the preparations were determined. Oxidative stability (120°C, 20 L/h) and DPPH radical scavenging were increased ～2–7 fold depending on the level of leaves used due to enrichment with polar phenols, mainly oleuropein, and a‐tocopherol. The extraction process affected the chlorophyll content and organoleptic traits as indicated by acceptability and preference tests (n = 50). Forty‐four % of the panelists identified a strong pungency in preparations with 15% w/w new leaves. Fifty‐four % of them identified a bitter taste in those with 15% w/w mature leaves, which was attributed to high levels of oleuropein (～200 mg/kg oil). Olive leaf‐olive oil preparations had interesting properties regarding antioxidants present that can attract the interest of a functional product market. Practical applications: The wider use of olive oil and derived products is highly desirable. In this sense, the current study presents data that support introduction to the market of a new specialty olive oil based solely on olive tree products (olive oil and leaves). Thus, in addition to olive oil and olive paste, a new product, that is an olive oil enriched with olive leaf antioxidants, especially oleuropein produced via a “green” technique (mechanical means instead of extraction with organic solvent) can be made available for consumers.     

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.     

Identification and classification of olive oils by high-resolution13C nuclear magnetic resonance

Unsaponifiable matter from 19 olive and olive pomace oils were studied by high-resolution¹³C nuclear magnetic resonance spectroscopy. Their spectra showed characteristic peaks that corresponded to molecular substructures rather than the individual constituents present in the unsaponifiable matter. The presence of squalene and other hydrocarbons, sterols and triterpenic alcohols, in addition to other groups of minor compounds, were observed. Based on the analysis of these spectra, it was possible to distinguish among different grades of olive oils by using stepwise discriminant analysis. This direct method of analysis is suggested to be used in artificial neural networks to define oil identity and quality.     

Effect of Alcalase™ on olive pomace protein extraction

The effect of Alcalase^™ treatment on olive pomace protein extraction has been studied. Alcalase improves protein extraction from 5 to 30% of total protein. This improvement is not accompained by an increase in degree of protein hydrolysis, probably because protease activity is inhibited by secondary metabolites and the substrate is highly denatured and resistant to hydrolysis. The increase in protein extraction is attributed to fiber solubilization as a result of secondary activities of Alcalase. Protein extracts with a high content of soluble fiber have improved functional properties, with respect to olive pomace, such as water and oil absorption. Emulsifying and foaming activities were inappreciable. The products obtained represent a suitable source of soluble fiber and protein and may contribute to the improvement of the economic status of olive pomace by-product.     

Effect of extraction systems on the quality of virgin olive oil

Research has been carried out to ascertai the effects of different processing systems on olive oil quality. Tests were performed in industrial oil mills that were equipped with both pressure and centrifugation systems. Results show that oils extracted from good-quality olives do not differ in free fatty acids, peroxide value, ultraviolet absorption and organoleptic properties. Polyphenols ando-diphenols contents and induction times are higher in oils obtained from good-quality olives by the pressure system because it does not require addition of water to the olive paste. The centrifugation system requires the addition of warm water to the olive paste and helps to obtain oils with a lower content of natural antioxidants. Oils obtained from poorquality or from ripe olives in continuous centrifugal plants are lower in free fatty acids than those obtained by the pressure system. Dr. Mario Solinas is deceased—May 23, 1993.     

Isolation and separation of tocopherols from olive by-products with supercritical fluids

Supercritical fluid extraction of olive pomace, the semisolid residue obtained using two-phase olive oil production systems, and supercritical fluid chromatographic separation of the extracts were performed to study the content of tocopherols, a group of compounds of interest for the food industry owing to their antioxidant activity. The developed method consists of supercritical CO₂ extraction at pilot plant scale and subsequent fractionation by two successive depressurizations. Enrichment of α-, β-, and γ-tocopherol was achieved in separator 2 when working at low densities in the first separator. Fractions obtained using high densities in separator 1 contained major proportions of triglycerides, waxes, and sterols. Tocopherols from olive by-products were separated and quantified in an environmentally friendly way by using supercritical fluid chromatography with packed capillary columns coated with polyethylene glycol and neat CO₂ according to a method previously optimized in our laboratory. The studied olive by-products can be considered a natural source of antioxidants because substantial concentration of tocopherols have been obtained in the extracts. The isolation and separation of tocopherols from olive pomace by applying supercritical fluid technology provides an interesting approach to exploit such by-products in an environmentally friendly way.     

Optimization of the Abencor system to extract olive oil from irrigated orchards

Studying the composition of olive oil requires cold‐press olive oil extraction. One of the most common laboratorial mills is the Abencor system. However, its operation protocol was formulated decades ago for Spanish olive varieties from traditionally rain‐fed orchards. We modified this protocol for use with “Barnea” and “Picual” olives from irrigated orchards that are characterized by high water content. Independent effects of malaxation time, temperature, water addition and talc addition on extraction efficiency, and major quality indices of virgin olive oil were studied. Overall, addition of talc to the fruit paste was the most significant treatment in terms of yield and quality of the oil although its effect was cultivar dependent. Improved oil yield was particularly significant for “Picual.” Extended malaxation time was also effective in improving oil extractability. Addition of talc generally improved oil‐quality parameters, while water addition had the opposite effect. Yet, quality parameters remained within the extra virgin level. Temperature increments reduced oil quality. The need to adapt a modified protocol for use with fruits from irrigated orchards that will facilitate critical comparison of results obtained from different agronomic theses and different laboratories is highlighted. It is recommended that each laboratory develops an appropriate protocol for the operation of the Abencor system in accordance to the characteristics of the olive fruit they are working with. Practical applications: Abencor system serves as the major laboratorial mill world‐wide. Those mills allow the researchers to characterize olive oil in accordance to the treatments received by the trees. This cannot be done in commercial mills. The system operation protocol was established decades ago for fruits from rain‐fed orchards. In the past decade there was a rapid increase in the use of irrigation in olive orchards and therefore it is crucial to optimize the operation protocol for fruit with relatively high water content. In the current work we have evaluated the influence of a series of technological parameters (i.e., talc and water addition, malaxation time, and temperature) on the extraction efficiency and quality indices of olive oil. This allowed us to present a modified protocol for the Abencor system operation suitable for olive fruit of irrigated orchards that will facilitate a reliable representation of the influence of different treatments on the yield and characteristics of the olive oil.     

New possibilities in California olive oil

Summary and Conclusions I. There is a field for increasing the return on oil olives through feeding the pomace to livestock, and through increasing the oil yield by the use of more powerful presses, or exhausting the oil content of the pomace by solvent extraction. II. Neutralization of free fatty acids and decolorization are refining methods that can be utilized at any plant, but deodorizing is a problem that will probably require special equipment. III. Work leading to the establishment of olive oil standards is suggested. IV. In the event of the establishment of standards, a central refining and blending plant is suggested.     

Characterization and chemometric study of crude and refined oils from table olive by‐products

Table olive processing produces defective fruits and the conditioning operations give rise to solid by‐products which are processed to obtain oil. In this study, the most relevant characteristics of crude oils extracted from table olive by‐products were high average acidity values (4.5%, green olives; 8.1%, ripe olives), ECN42 values of 0.34 (green olives) and 0.10 (ripe olives), while 2‐mono‐palmitin averaged 0.92%. The overall content of sterols was 2257 mg/kg (green olives) and 1746 mg/kg (ripe olives), while the concentration of cholesterol was 36 mg/kg (green olives) and 19 mg/kg (ripe olives). The effect of refining was mainly reflected by a decrease in acidity and sterols. Although most characteristics were in agreement with the established regulation for olive oil, the overall trans fatty acid content, the low apparent β‐sitosterol content, and the relatively high cholesterol content prevented their inclusion into classes of crude or refined lampante or pomace olive oils, not even into the vegetable oil category. Therefore, the oils analyzed should be considered for non‐edible purposes. The physicochemical characteristics used for chemometric discrimination permitted discrimination among types of oils (crude, 100%; physically refined, 90%; chemically refined, 100%), elaboration styles (green and ripe olives, 100%) and cultivars (Gordal, Manzanilla, Hojiblanca and Cacereña, 100%), with the sterol composition being the most useful parameter for discrimination.     

On the quality control of ‘olive paste’, a specialty based on olives and olive oil

‘Olive paste’ is a preserved food gaining popularity as a gourmet product. Its quality depends on that of the major ingredients, table olives (green or black) and virgin olive oil, as well as on the changes occurring to the constituents of the latter during preparation and storage. In this view, our attention was focused on the characteristics of the lipid fraction (l.f.) of a great number of commercial products after a careful search in retail markets and the web. Ultraviolet absorbance values (K₂₃₂, K₂₇₀) of the l.f., a criterion set for edible and non‐edible olive oil oxidative status due to paste heat treatment during pasteurization, could not support the label information regarding the quality of the oil used. On the contrary, the content of α‐tocopherol (?250 mg/kg l.f. or ?50 mg/kg paste) was a strong indication of good‐quality major ingredients. Within each brand, consistency with labeling was checked through squalene (higher content in products containing higher amounts of olive oil) or β‐carotene determination (higher levels in preparations containing red pepper). For green olive paste samples, the values of the ratio pheophytin a/pyropheophytin a may be used to monitor the shelf life of the product. The findings support routine quality control of the new product.     

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.