Ramón Aparicio-Ruiz

Authentication of vegetable oils by chromatographic techniques

Food authentication has been evolving continually to situations that were basically governed by a global market trend. Analytical techniques have been developed or modified to give plausible solutions to the devious adulterations at each moment. Classical tests have largely been replaced with newer technical procedures, most of which are based on gas chromatography, with some being based on high-performance liquid chromatography. Determination of trans-fatty acid and sterolic composition, together with sterol-dehydration products, have been used most frequently used to detect contamination and adulteration. Sophisticated new adulterations, e.g., olive oil with hazelnut oil, represent a new challenge for the next millennium, although suggestive proposals for detecting these kinds of adulterations are emerging with the contribution of databases and mathematical algorithms.

Relationship between sensory attributes and volatile compounds qualifying dry-cured hams.

This work studies the relationship between 45 volatile compounds and 17 sensory attributes (13 flavour perceptions) of dry-cured hams. Volatile compounds were quantified by SPME-GC while the sensory assessment was carried out by 13 panellists. GC-sniffing was used to determine the odour impact zones of the chromatogram. The odour thresholds of the volatile compounds and their sensory characterisation were determined by dilution analysis. Six sensory attributes (acorn odour and flavour, rancid odour, rancid taste, fat rancid and fat pungent flavours) were explained by regression equations (adjusted -R(2)⩾0.70) based on ten compounds: benzaldehyde, 2-heptanone, hexanal, hexanol, limonene, 3-methylbutanal, 3-methylbutanol, 2-nonanone, octanol, pentanol. Acorn flavour attribute was successfully emulated by mixing the volatile compounds selected by the equation. Its odour was evaluated by assessors that gave a sensory description that matches with the target. All the procedures performed for the elucidation of volatile-attribute relations showed a basic agreement in their results.

Validation of SPME-GCMS method for the analysis of virgin olive oil volatiles responsible for sensory defects

Volatile compounds are responsible for the aroma of virgin olive oil and also for its quality. The high number and different nature of volatile compounds drive to the need of a reliable analytical method that allows their proper quantification to explain the standard method of panel test. Although there are some analytical solutions available, they have not been validated and the regulatory bodies are reluctant to adopt them since they can be subjected to unknown errors. In this regards, the European Union has encouraged the validation of these analytical tools through the research program Horizon2020, which involves gaining knowledge from the analytical properties of the chemical methods for sensory assessment. This work is focused on the analytical validation of the methodology used to determine the actual concentration of volatiles in virgin olive oils when applying SPME-GCMS. The validation process includes the calibration curves for 29 volatile compounds responsible for the most common sensory perceptions in virgin olive oils, the determination of their working ranges with linear response, the detection and quantification limits, the sensitivity, the accuracy estimated as trueness and precision and the selectivity. Sixty-seven percent of the compounds presented a relative standard deviation in repeatability lower than 10%, and this percentage rises to 95% in lampante virgin olive oils. The accuracy was established in 97% of the studied volatile compounds. Finally, an empirical example of the ability of the method to discriminate virgin olive oils of different categories (extra virgin, virgin, ordinary and lampante) by the quantification of their volatiles is provided.

Thermal degradation kinetics of chlorophyll pigments in virgin olive oils. 1. Compounds of series a.

Virgin olive oils (VOO) collected at three maturation stages were thermodegraded to determine the degradation kinetics of series a chlorophyll pigments. The proposed degradation mechanism involves reactions that alter the structure of the isocyclic ring of pheophytin, originating intermediary products such as pyropheophytin, 13(2)-OH-pheophytin, and 15(1)-OH-lactone-pheophytin, and reactions that affect the porphyrin ring, producing colorless compounds. The marked effect of temperature has been pointed out in these competitive processes with the formation of pyropheophytin and the significantly higher value of its kinetic constant. No significant effect of the oily medium on the reaction mechanisms of pyropheophytin and 15(1)-OH-lactone-pheophytin has been found, comparing kinetic and thermodynamic parameters determined in the three VOO matrices of different pigment contents (high, medium, and low). The reaction mechanism of 13(2)-OH-pheophytin, by contrast, was affected by the medium; the reaction rate was the same for all of the matrices only at the isokinetic temperature (51 degrees C).

Pigment Profile in Non-Spanish Olive Varieties (Olea europaea L. Var. Coratina, Frantoio, and Koroneiki)

The analysis, for the first time, of the chlorophyll and carotenoid profile of olive fruits of the varieties Coratina, Frantoio, and Koroneiki has revealed important differences with Spanish varieties. First, a high chlorophylls/carotenoids ratio and a low chlorophyll a/b ratio imply that the photosynthetic apparatus has structural differences with respect to other olive varieties; second, in the carotenoid fraction, a low percentage of lutein, a high percentage of beta-carotene, and a high content in neoxanthin are signs that in these three olive varieties the carotenoid biosynthetic pathway is displaced, favoring the beta,beta series over the alpha,beta series. These differences in the chlorophyll and carotenoid profiles of the fruit are reflected in the corresponding virgin olive oils. It is proposed that the limits of the pigmentary parameters of authenticity of virgin olive oil previously established for the Spanish varieties be extended to obtain markers at a general level, independent of the geographical origin.

In-Depth Assessment of Analytical Methods for Olive Oil Purity, Safety, and Quality Characterization

This paper evaluates the performance of the current analytical methods (standard and widely used otherwise) that are used in olive oil for determining fatty acids, triacylglycerols, mono- and diacylglycerols, waxes, sterols, alkyl esters, erythrodiol and uvaol, tocopherols, pigments, volatiles, and phenols. Other indices that are commonly used, such as free acidity and peroxide value, are also discussed in relation to their actual utility in assessing quality and safety and their possible alternatives. The methods have been grouped on the basis of their applications: (i) purity and authenticity; (ii) sensory quality control; and (iii) unifying methods for different applications. The speed of the analysis, advantages and disadvantages, and multiple quality parameters are assessed. Sample pretreatment, physicochemical and data analysis, and evaluation of the results have been taken into consideration. Solutions based on new chromatographic methods or spectroscopic analysis and their analytical characteristics are also presented.

Sensor responses to fat food aroma: A comprehensive study of dry-cured ham typicality

The physicochemical phenomena that explain the sensing mechanisms of gas sensors have been extensively investigated. Nevertheless, it is arduous to interpret the sensor signals in a practical approach when they response to complex mixtures of compounds responsible for food aroma. Thus, the concomitant interactions between the volatiles and the sensor give up a single response affected by synergic and masking effects between compounds. An experimental procedure is proposed to determine the individual contribution of volatile compounds in the sensor response, illustrated with the examples of aroma of dry-cured hams and metal oxide sensors. The results from mathematical correlations and the analyses of pure standards are previously analyzed to describe the behavior of sensors when interacting with individual compounds. A sensor based olfactory detector (SBOD) entailing the use of a capillary column connected to a sensor array as non-destructive detector in parallel with the flame detector served to provide definitive information about the individual contribution of volatile compounds to sensor responses. The sensor responses in this system, which is referred to as sensorgram, were interpreted by taking into account the volatile composition of the samples determined by GC.

Chromatographic Methodologies: Compounds for Olive Oil Color Issues

Virgin olive oil (VOO) is consumed without a further refining process, thus retaining minor compounds that give rise to a fragrant and delicate flavor. Volatile compounds are responsible for VOO aroma, playing an important role in its sensory quality. A wide range of compounds, from qualitative and quantitative points of view, has been described in VOO aroma. Different routes are implicated in their production, and the biochemical pathways leading to the formation of volatiles, including the lipoxygenase pathway as the most relevant, are described. The preferred technique for the analysis of volatiles is gas chromatography, which requires an adequate sample preparation procedure, usually including a preconcentration step. The chapter considers the main drawbacks of the analysis of volatile compounds and describes the most commonly used method in the analysis of olive oil, from traditional to current procedures, such as solid-phase microextraction or headspace sorptive extraction. In the search for an alternative to the time-consuming chromatographic procedures, chemosensor-based methodologies have been implemented using various kinds of sensors, and the application of metal oxide semiconductor sensors, conducting polymer sensors, and acoustic sensors and their results are reviewed in the chapter. The establishment of the relationship between chemical compounds and sensory attributes is the most complex aspect of flavor study. The contribution of volatile compounds to the sensory quality of VOO is discussed. The relationship between volatile compounds and the basic sensory perceptions of VOO, by using the statistical sensory wheel, is treated in depth. The main reason for the presence of sensory defects is the formation of certain volatile compounds that can be produced by overripening of the fruit, oxidation of the unsaturated fatty acids, or attack by molds and bacteria, and the chemical compounds responsible for the main sensory defects detected in VOOs are discussed. The most recent results in the evaluation of sensory descriptors and the research on brain activity induced by pleasant and unpleasant VOO aromas are analyzed as well.

Mathematical model to predict the formation of pyropheophytin a in virgin olive oil during storage.

A mathematical model has been developed that describes the changes of pyropheophytin a (pyphya) in virgin olive oil (VOO). The model has been created using multivariate statistical procedures and is used in the prediction of the stability and loss of freshness of VOO. An earlier thermokinetic study (Aparicio-Ruiz, R.; Mı́nguez-Mosquera, M. I.; Gandul-Rojas, B. Thermal degradation kinetics of chlorophyll pigments in virgin olive oils. 1. Compounds of series a. J. Agric. Food Chem.2010, 58, 6200-6208) that looked at the characterization of the degradation of pheophytin a (phya), the main chlorophyll compound in VOO and a precursor of pyphya, allowed the authors to obtain the kinetic parameters necessary for mathematically expressing the percentage of pyphya, according to the time and temperature of storage using the Arrhenius model. Data regarding the percentage of pyphya obtained during the actual degradation of VOO in darkness, at room temperature and with a limited supply of oxygen, has allowed the mathematical prediction model to be validated. Using average monthly temperatures in the calculation of kinetic constants, theoretical data are obtained that are generally found to be within 95% confidence levels of experimental data.

Thermal Degradation Kinetics of Neoxanthin, Violaxanthin and Antheraxanthin in Virgin Olive Oils

A first-order kinetic mechanism was appropriate for describing the thermal degradation of epoxy xanthophylls in virgin olive oil (VOO). Consecutive reactions that involve reorganization of 5,6-epoxide groups to 5,8-furanoxide groups and subsequent rupture of the polyene chain occurred in the degradation pathways. Thermal stability was significantly affected by changes in the chemical structure (epoxy to furanoid structure), being the greatest stability for neoxanthin. A true kinetic compensation effect was found in a series of similar reactions, that is, the degradation of 5,8-furanoxides into colorless products. An isokinetic study in different VOO matrices showed that the oily medium did not significantly affect the reaction mechanisms. Consequently, the kinetic parameters obtained as temperature functions according to the Arrhenius model can be used to develop a prediction mathematical model for 5,8-furanoxide xanthophylls in VOO over time. The potential usefulness of the parameter neoxanthin/neochrome ratio is discussed as a chemical marker of heat treatment in VOO.