Authenticity Assessment of Extra Virgin Olive Oil: Evaluation of Desmethylsterols and Triterpene Dialcohols

Extra virgin olive oil (EVOO) has a long history of economic adulteration, the detection of which presents significant challenges due to the diverse composition of cultivars grown around the world and the limitations of existing methods for detecting adulteration. In this study, using Method COI/T.20/Doc. No. 30/Rev. 1 of the International Olive Council, the authenticity of 88 market samples of EVOO was evaluated by comparing total sterol contents, desmethylsterol composition, and contents of triterpene dialcohols (erythrodiol and uvaol) with purity criteria specified in the United States Standards for grades of olive oil and olive‐pomace oil. Three of the 88 samples labeled as EVOO failed to meet purity criteria, indicating possible adulteration with commodity oil and/or solvent‐extracted olive oil. Detection of adulteration was also evaluated by spiking an EVOO sample with commodity oil at the 10 % level. As expected, eight of the spiked samples (canola, corn, hazelnut, peanut, safflower, soybean, and sunflower oils, and palm olein) failed to meet purity criteria. Two of the three samples spiked with 10 % hazelnut oil went undetected for adulteration. Overall, a low occurrence rate of adulteration (<5 %), based on purity criteria for desmethylsterols and triterpene dialcohols, was detected for the 88 products labeled as EVOO.     

Precision and accuracy in the color specification of virgin olive oils from the bromthymol blue method

Twenty experienced observers with nondefective color vision judged 27 virgin olive oil samples within an acceptable color range, using the bromthymol blue (BTB) method, under controlled observation conditions (daylight source with a correlated color temperature of 6500 K, and standard gray back-ground). On the average, 44.8% of the observers agreed in their selections of the BTB standard solution matching a given oil sample, and this percentage increased to 88.2% considering ±one step in the two dimensions (pH and concentration) of the BTB scale. On the average, the lowest color difference between oil samples and available BTB solutions was 6.6 Commission Internationale de l'éclairage 1976-(L^*a^*b^*) (CIELAB) units, but this color difference was approximately two times greater for the color difference between oil samples and BTB solutions selected by our observers. The colors of the BTB standard solutions in the CIELAB space are not uniformly distributed, and thus one step in pH or concentration is equivalent to CIELAB color differences varying in a wide range (1.7–13.5 and 1.7–26.3 CIELAB units, respectively). From these values, indicating low precision, accuracy, and uniformity, some suggestions are made for future improvements of the current BTB method.     

Pinoresinol and 1-acetoxypinoresinol, two new phenolic compounds identified in olive oil

Polyphenols of olive oil show autoprotective, sensory, and nutritional-therapeutic effects. Two new phenolic compounds have been isolated from virgin olive oils by preparative high-performance liquid chromatography and their structures established on the basis of their mass spectra and nuclear magnetic resonance spectral data. The compounds identified are the lignans pinoresinol and 1-acetoxypinoresinol. Both have been found in all the commercial virgin olive oils analyzed. Pinoresinol concentration was rather similar in all the oils. In contrast, 1-acetoxypinoresinol concentration was higher in oils of the Arbequina and Empeltre cultivars than in Picual or Picudo cultivars. Pinoresinol and 1-acetoxypinoresinol may represent the major phenolic compounds in some Arbequina and Empeltre oils. Lignans possess biological and pharmacological properties and, therefore, the two new compounds identified in olive oils may contribute to the reported beneficial effects which are attributed to polyphenols on human health of a diet rich in olive oil.     

Treatment of olive mill washing water by ultrafiltration

Olive oil production requires important quantities of washing water containing low oil concentrations, but classical processes used to recover or to eliminate this oil are ineffective. This study presents a membrane technique to treat olive oil mill washing water using different commercial ultrafiltration membranes: one organic (PCI) and two ceramic (Ceraver) membranes. The influence of the hydrodynamic parameters (transmembrane pressure and flow rate) and the cut‐off membranes on the efficiency of the ultrafiltration process was evaluated, and it was shown the organic PCI membrane could reduce pollution due to organic matter by decreasing the value of the Chemical oxygen demand by about 90%. Moreover, the nature of the ultrafine pore membrane appeared to be an important parameter which may strongly increase or decrease the capacity of the membrane. The membrane cut‐off did not have a strong influence on the performance of the process but if the membrane pores were too large the stability of the dynamically formed membrane decreased at transmembrane pressures greater than 0.2 MPa.     

蔗渣纤维素氨基甲酸酯的合成

使用平均聚合度为548的蔗渣浆粕和尿素为原料,在二甲苯溶剂中,探讨各种工艺条件对产物氮含量的影响,制备了溶解性和稳定性较好的蔗渣纤维素氨基甲酸酯。产物用红外光谱和热重曲线进行结构和热性质分析,结果表明,蔗渣纤维素在羟基上发生了衍生化反应,引入了"-CONH2"基团;与原料蔗渣浆粕相比,在热裂解前蔗渣纤维素氨基甲酸酯存在更明显的小分子的热分解现象。     

Evaluation of vitamin E by HPLC in a variety of olive-based foodstuffs

A survey of vitamin E levels in a wide variety of olive-based foodstuffs was conducted. Vitamin E was determined by normal-phase HPLC. The only form of vitamin E found in all commercial presentations of table olives was α-tocopherol, with an average content of 3.1 mg/100 g edible portion. A very low content (<0.4 mg/100 g edible portion) of γ-tocopherol was found in most of the samples analyzed. The main sources of variation of vitamin E were olive cultivars and commercial presentations. Processing type (Spanish style green olives, directly brined olives, ripe olives) had a limited influence. Irrespective of the elaboration style, the Gordal cultivar was the poorest with respect to the vitamin E content. On the other hand, all commercial presentations based on the Hojiblanca cultivar had high contents of vitamin E. The results of this study may be used by the industry for requirements of nutritional labeling or by nutritionists to estimate vitamin E intakes in diets that include table olives.     

Ultrafine grinding of sugar cane bagasse ash for application as pozzolanic admixture in concrete

Sugar cane bagasse ash, a byproduct of sugar and alcohol production, is a potential pozzolanic material. However, its effective application in mortar and concrete requires first the controlled use of grinding and classification processes to allow it to achieve the fineness and homogeneity that are required to meet industry standards. The present paper investigates the role of mill type and grinding circuit configuration in grinding in laboratory- and pilot plant-scale on the particle size, specific surface area and pozzolanic activity of the produced ashes. It was observed that, although different size distributions were produced by the different mills and milling configurations, the pozzolanic activity of the ground ash was directly correlated to its fineness, characterized by its 80% passing size or Blaine specific surface area. From a low pozzolanic activity of less than 50% of the as-received ash, values above 100% could be reached after prolonged grinding times. Electric power requirements to reach the minimum pozzolanic activity were estimated to be in the order of 42 kWh/t in an industrial ball mill. Incorporation of an ultrafinely-ground ash in a high-performance concrete in partial replacement of Portland cement (10, 15 and 20% by mass) resulted in no measurable change in mechanical behavior, but improved rheology and resistance to penetration of chloride ions.     

Kinetics and Thermodynamics of Oil Extraction from Olive Cake

The kinetics of oil extraction from olive cake by using ethanol 96% was studied for different solvent-to-solids ratios and temperatures. The thermodynamic aspect of the extraction process was also examined. In the kinetic study, the results produced by the model of So and Macdonald (a model involving two main mechanisms of oil extraction: a washing process and a diffusion process with two stages) were found to be in good agreement with the experimental data. The yield of oil in the extract increased with increasing contact time, solvent-to-solids ratio and extraction temperature. The calculated values of the mass transfer coefficients of various stages of the extraction were found to increase linearly with solvent-to-solids ratio and temperature. In all cases, the predominant mechanism in the extraction was the washing of the oil occurring on the particle surface. The values of the activation energy were 8.56 kJ mol⁻¹ for the washing stage, 9.88 kJ mol⁻¹ for the first stage of diffusion and 17.55 kJ mol⁻¹ for the second stage of diffusion by changing temperature from 20 to 50 °C. Further, the results obtained from thermodynamic study of extraction process gave positive values of enthalpy and entropy changes and negative values of change in free energy. Under the equilibrium conditions, the temperature coefficient was found to be 1.02.     

Effect of olive fruit freezing on oxidative stability of virgin olive oil

Several studies have suggested that the phenolic fraction plays an important role during storage and therefore in the shelf life of virgin olive oil. This investigation examines the effect of freezing olives (–18 °C) before processing into oil on the transfer of the phenolic compounds into the subsequent oil, and the consequential changes in oxidative stability. Oil samples obtained from frozen olives (24 h at –18 °C), crushed with and without preliminary thawing, were compared to a control sample; both oils were obtained using a two‐phase low‐scale mill. The oxidative stability in different samples was assessed in terms of primary and secondary oxidation products as measured by peroxide values and oxidative stability index times, respectively. The quality of the oil samples was also checked through the percentage of free acidity and the phenolic content. Phenols were determined by both spectrophotometric assays (total phenols and o‐diphenols) and HPLC‐DAD/MSD. The antiradical capacity of the phenolic fraction was determined by DPPH and ABTS spectrophotometric tests. These analyses showed that thawing of olives before oil extraction led to a significant loss of oxidative stability and phenols; in contrast, samples obtained from frozen olives that were not thawed before crushing showed qualitative characteristics similar to control samples.     

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.