Novel Analytical Methods to Evaluate Quality and Authenticity of Edible Oils and Fats

A special issue of Foods (ISSN 2304-8158). This special issue belongs to the section "Food Quality and Safety".

Deadline for manuscript submissions: closed (20 February 2022) | Viewed by 23358

Special Issue Editors


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Guest Editor
Department of Characterization and Quality of Lipids, Instituto de la Grasa (CSIC), Sevilla, Spain
Interests: alternative oil sources; analytical procedures; edible fats and oils; microencapsulation processes; oil components; oil regulations

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Guest Editor
Department of Characterization and Quality of Lipids, Instituto de la Grasa (CSIC), Sevilla, Spain
Interests: 3MCPD; chloropropanols; contaminants; glycidol; lipidic matrix; MOSH-MOAH; olive oil fraud detection; olive oil quality

E-Mail Website
Guest Editor
Department of Characterization and Quality of Lipids, Instituto de la Grasa (CSIC), Sevilla, Spain
Interests: authenticity; method development; olive oil; quality; residues and contaminants

Special Issue Information

Dear Colleagues,

Quality and authenticity of edible oils and fats can be analytically determined. In this respect, there are many methods included in national and international regulations, most of which are based on the chemical composition of previously characterized edible oils and fats.

Olive oil is one of the healthiest edible oils that exists, also being the one with the most comprehensive legislation up to date, to control both its quality and authenticity. Several international regulatory bodies such as the International Olive Council, the Codex Alimentarius, and the corresponding bodies of the European Union, United States of America, State of California, Australia, and South Africa have legislation or standards regarding the quality and the genuineness characteristics of olive oils. Special edible oils such as Avocado, Argan or Sacha inchi also have their own regulations in their main producing countries (Mexico, Morocco, and Peru, respectively).

The analytical methods included in the regulations or standards are under continuous development, optimizing, improving or even using new technologies for the analyses. The limits included in the regulations are also periodically reviewed considering new producing countries or the effects of the climatic change.

Chromatographic techniques (GC and HPLC) are the most used approaches to either characterize or control edible oils and fats. Mass spectrometry, NMR or NIR spectroscopy were introduced some time ago to characterize or to evaluate the quality of edible oils and fats, although they are not included in any regulation. Today, emerging techniques such as ultrahigh performance liquid chromatography (UHPLC), together with headspace solid-phase microextraction–gas chromatography–mass spectrometry (HS-SPME-GC-MS), online HPLC-GC or electrospray ionizatio–high-resolution mass spectrometry, or even genomic approaches, using quantitative real-time PCR are being developed to characterize and control edible oils and fats. Many of these techniques are in-house validated with results so promising that they might be adopted by regulatory bodies in the near future.

Dr. M. Carmen Pérez-Camino
Dr. Raquel B. Gómez-Coca
Dr. Wenceslao Moreda
Guest Editors

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Keywords

  • analytical techniques
  • chromatographic techniques
  • edible oils and fats
  • emerging techniques
  • regulations
  • NMR
  • genomic
  • HRMS
  • HPLC-GC
  • standard methods

Published Papers (7 papers)

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Research

25 pages, 4264 KiB  
Article
Study of the Evolution of Pigments from Freshly Pressed to ‘On-the-Shelf’ Extra-Virgin Olive Oils by Means of Near-UV Visible Spectroscopy
by Eleonora Borello, Daniele Roncucci and Valentina Domenici
Foods 2021, 10(8), 1891; https://doi.org/10.3390/foods10081891 - 15 Aug 2021
Cited by 9 | Viewed by 3808
Abstract
Spectroscopic non-destructive methods have high potentialities as fast, cheap and easy-to-be-used approaches to address olive oil quality and authenticity. Based on previous research where near-UV Visible spectroscopy was used to investigate extra-virgin olive oils (EVOOs) and their main pigments’ content (i.e., β-carotene, lutein, [...] Read more.
Spectroscopic non-destructive methods have high potentialities as fast, cheap and easy-to-be-used approaches to address olive oil quality and authenticity. Based on previous research where near-UV Visible spectroscopy was used to investigate extra-virgin olive oils (EVOOs) and their main pigments’ content (i.e., β-carotene, lutein, pheophytin a and pheophytin b), we have implemented the spectral deconvolution method in order to follow the EVOO’s life, from ‘freshly pressed’ to ‘on-the-shelf’ EVOO samples at different storage time. In the first part of the manuscript, the new implemented deconvolution spectroscopic method aimed to quantify two additional pigments, namely chlorophyll a and chlorophyll b, is described and tested on ‘ad hoc’ samples with known concentrations of chlorophylls. The effect of light exposure and acidification was investigated to test the reliability and robustness of the spectral deconvolution. In the second part of the work, this approach was used to study the kinetic of pigments’ degradation in several monocultivar fresh EVOO samples under optimal storage’s conditions. The results here reported show that this spectroscopic deconvolution approach is a good method to study fresh EVOOs too; moreover, the proposed method revealed to be sensitive to detect eventual stresses of olive oil samples stored in not-good conditions. Full article
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12 pages, 1065 KiB  
Article
In-House Validation of an SPE-GC-FID Method for the Detection of Free and Esterified Hydroxylated Minor Compounds in Virgin Olive Oils
by Enrico Valli, Andrea Milani, Ana Srbinovska, Erica Moret, Sabrina Moret, Alessandra Bendini, Wenceslao Moreda, Tullia Gallina Toschi and Paolo Lucci
Foods 2021, 10(6), 1260; https://doi.org/10.3390/foods10061260 - 2 Jun 2021
Cited by 5 | Viewed by 2715
Abstract
Minor compounds in vegetable oils are distributed between free and esterified forms, and the ratio of these two fractions could represent an important parameter for assessment of oil authenticity. A simple method based on offline SPE-GC-FID for the analysis of free and esterified [...] Read more.
Minor compounds in vegetable oils are distributed between free and esterified forms, and the ratio of these two fractions could represent an important parameter for assessment of oil authenticity. A simple method based on offline SPE-GC-FID for the analysis of free and esterified hydroxylated minor compounds in olive and sunflower oils has been developed and in-house validated. A satisfactory repeatability relative standard deviation (<7.5%) was obtained in all cases. The method, which requires simple instrumentation, allows for reliable quantification in a single chromatographic run with the advantages of minimizing sample manipulation, use of toxic solvents and reagents, and time consumption. The analytical procedure was applied to pure oil samples, including 15 authentic extra virgin olive oils collected from different European countries (Spain, Italy, Greece, and Portugal). Finally, the proposed SPE-GC-FID methodology could detect changes in the ratio between the free and esterified forms in pure extra virgin olive oil when mixed with refined sunflower oil at different percentages of 2, 5, 10, 15, and 20% (w/w) to simulate adulteration. Full article
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17 pages, 889 KiB  
Article
Formulations of Rancid and Winey-Vinegary Artificial Olfactory Reference Materials (AORMs) for Virgin Olive Oil Sensory Evaluation
by Ramón Aparicio-Ruiz, Sara Barbieri, Tullia Gallina Toschi and Diego L. García-González
Foods 2020, 9(12), 1870; https://doi.org/10.3390/foods9121870 - 15 Dec 2020
Cited by 8 | Viewed by 2871
Abstract
Sensory assessment of virgin olive oil (“panel test”) is the only sensory method included in international regulations of edible oils and its application is compulsory. Even if its application has been a success in quality control, improving the quality of virgin olive oils [...] Read more.
Sensory assessment of virgin olive oil (“panel test”) is the only sensory method included in international regulations of edible oils and its application is compulsory. Even if its application has been a success in quality control, improving the quality of virgin olive oils over the last 30 years, at present, there is no reference material (RM), in the strict sense of the term, to be used as a validated standard for sensory defects of virgin olive oil with which tasters can be trained. Usually, real samples of virgin olive oils assessed by many panels for the International Olive Council (IOC) ring tests are used as materials of reference in panel training and control. The latter are highly representative of the main perceived defects, but availability is limited, samples are not homogeneous year after year, and other secondary defects can be present. Thus, in order to provide solutions, this work describes an analytical procedure for implementing olfactory formulations that emulate rancid and winey-vinegary defects found in virgin olive oils with the aim of providing reproducible RMs that can be prepared on demand. A strategy for designing RMs for aroma is presented and the optimization process to obtain the best formulation is described. Under the criteria of representativeness, verified with the advice of the IOC, aroma persistence, and simplicity in formulation, two RMs for winey-vinegary and rancid were obtained by diluting acetic acid and ethanol (winey-vinegary defect) and hexanal (rancid defect) together with other compounds that are used to modify aroma and avoid non-natural sensory notes. Full article
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20 pages, 4067 KiB  
Article
Monitoring Virgin Olive Oil Shelf-Life by Fluorescence Spectroscopy and Sensory Characteristics: A Multidimensional Study Carried Out under Simulated Market Conditions
by Ana Lobo-Prieto, Noelia Tena, Ramón Aparicio-Ruiz, Diego L. García-González and Ewa Sikorska
Foods 2020, 9(12), 1846; https://doi.org/10.3390/foods9121846 - 11 Dec 2020
Cited by 22 | Viewed by 2580
Abstract
The control of virgin olive oil (VOO) freshness requires new tools that reflect the diverse chemical changes that take place during the market period. Fluorescence spectroscopy is one of the techniques that has been suggested for controlling virgin olive oil (VOO) freshness during [...] Read more.
The control of virgin olive oil (VOO) freshness requires new tools that reflect the diverse chemical changes that take place during the market period. Fluorescence spectroscopy is one of the techniques that has been suggested for controlling virgin olive oil (VOO) freshness during its shelf-life. However, a complete interpretation of fluorescence spectra requires analyzing multiple parameters (chemical, physical–chemical, and sensory) to evaluate the pace of fluorescence spectral changes under moderate conditions with respect to other changes impacting on VOO quality. In this work, four VOOs were analyzed every month with excitation–emission fluorescence spectra. The same samples were characterized with the concentration of fluorophores (phenols, tocopherols, chlorophyll pigments), physical–chemical parameters (peroxide value, K232, K270, free acidity), and sensory attributes (medians of defects and of the fruity attribute). From the six components extracted with parallel factor analysis (PARAFAC), two components were assigned to chlorophyll pigments and those assigned to tocopherols, phenols, and oxidation products were selected for their ability to discriminate between fresh and aged oils. Thus, the component assigned to oxidation products correlated with K270 in the range 0.80–0.93, while the component assigned to tocopherols–phenols correlated with the fruity attribute in the range 0.52–0.90. The sensory analysis of the samples revealed that the changes of these PARAFAC components occurred at the same time as, or even before, the changes of the sensory characteristics. Full article
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14 pages, 735 KiB  
Article
Supporting the Sensory Panel to Grade Virgin Olive Oils: An In-House-Validated Screening Tool by Volatile Fingerprinting and Chemometrics
by Beatriz Quintanilla-Casas, Marco Marin, Francesc Guardiola, Diego Luis García-González, Sara Barbieri, Alessandra Bendini, Tullia Gallina Toschi, Stefania Vichi and Alba Tres
Foods 2020, 9(10), 1509; https://doi.org/10.3390/foods9101509 - 21 Oct 2020
Cited by 21 | Viewed by 3970
Abstract
The commercial category of virgin olive oil is currently assigned on the basis of chemical-physical and sensory parameters following official methods. Considering the limited number of samples that can be analysed daily by a sensory panel, an instrumental screening tool could be supportive [...] Read more.
The commercial category of virgin olive oil is currently assigned on the basis of chemical-physical and sensory parameters following official methods. Considering the limited number of samples that can be analysed daily by a sensory panel, an instrumental screening tool could be supportive by reducing the assessors’ workload and improving their performance. The present work aims to in-house validate a screening strategy consisting of two sequential binary partial least squares-discriminant analysis (PLS-DA) models that was suggested to be successful in a proof-of-concept study. This approach is based on the volatile fraction fingerprint obtained by HS-SPME–GC–MS from more than 300 virgin olive oils from two crop seasons graded by six different sensory panels into extra virgin, virgin or lampante categories. Uncertainty ranges were set for the binary classification models according to sensitivity and specificity by means of receiver operating characteristics (ROC) curves, aiming to identify boundary samples. Thereby, performing the screening approach, only the virgin olive oils classified as uncertain (23.3%) would be assessed by a sensory panel, while the rest would be directly classified into a given commercial category (78.9% of correct classification). The sensory panel’s workload would be reduced to less than one-third of the samples. A highly reliable classification of samples would be achieved (84.0%) by combining the proposed screening tool with the reference method (panel test) for the assessment of uncertain samples. Full article
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15 pages, 1298 KiB  
Article
Pyropheophytin a in Soft Deodorized Olive Oils
by Raquel B. Gómez-Coca, Mahmoud Alassi, Wenceslao Moreda and María del Carmen Pérez-Camino
Foods 2020, 9(8), 978; https://doi.org/10.3390/foods9080978 - 23 Jul 2020
Cited by 6 | Viewed by 2569
Abstract
Mild refined olive oil obtained by neutralization and/or by soft deodorization at a low temperature and its blending with extra virgin olive oil (EVOO) is not allowed and is difficult to detect. Chlorophyll derivatives, pheophytins and pyropheophytin, and their relative proportions were proposed [...] Read more.
Mild refined olive oil obtained by neutralization and/or by soft deodorization at a low temperature and its blending with extra virgin olive oil (EVOO) is not allowed and is difficult to detect. Chlorophyll derivatives, pheophytins and pyropheophytin, and their relative proportions were proposed as parameters to detect such processes. The objective of this study is to determine changes in EVOO, in terms of pheophytins and pyropheophytin, occurring after several well-controlled mild refining processes. The changes on those chlorophyll pigments due to the processes depend on the temperature, stripping gas, acidity and oil nature. The data obtained show that, at temperatures below 100 °C, the rate at which pyropheophytin a is formed (Ra) is lower than the rate at which pheophytins a+a’ disappear (Ra+a’). As a consequence, the Ra+a’ and Ra ratios are considered to be directly linked to pheophytins a+a’ decrease instead of to pyropheophytin a formation. Stripping gas very slightly affects the transformation of the chlorophyll pigments; actually both acidity and N2 enhance the increment in the Ra+a’ and Ra ratios. In relation to the oil nature, the higher the initial pheophytin a+a’ content, the higher the increase in the Ra+a’ and Ra relations. Full article
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11 pages, 503 KiB  
Article
Fatty Acid Ethyl Esters in Virgin Olive Oils: In-House Validation of a Revised Method
by Rosa Palagano, Enrico Valli, Matilde Tura, Chiara Cevoli, María del Carmen Pérez-Camino, Wenceslao Moreda, Alessandra Bendini and Tullia Gallina Toschi
Foods 2020, 9(7), 924; https://doi.org/10.3390/foods9070924 - 14 Jul 2020
Cited by 3 | Viewed by 3523
Abstract
The content of fatty acid ethyl esters (FAEEs) is one of the quality parameters to define if an olive oil can be classified as extra virgin as these compounds are considered markers for virgin olive oils obtained from poor-quality olives. In addition, FAEEs [...] Read more.
The content of fatty acid ethyl esters (FAEEs) is one of the quality parameters to define if an olive oil can be classified as extra virgin as these compounds are considered markers for virgin olive oils obtained from poor-quality olives. In addition, FAEEs can also be indirect markers to detect soft deodorization treatment. In this study, an off-line HPLC-GC-FID method for determination of FAEEs is presented, revising the preparative step and the GC injector required by the official method (EU Reg. 61/2011). After optimization, the method was validated in-house by analyzing several parameters (linearity, limit of detection LOD, limit of quantification LOQ, robustness, recovery, precision, and accuracy) to determine its effectiveness. Linearity was measured in the 2.5–50 mg/L range; furthermore, intra-day and inter-day precision values were lower than 15%, while the LOD and LOQ were lower than 1 and 1.5 mg/kg, respectively, for all compounds considered. The main advantages of this revised protocol are: (i) significant reduction in time and solvents needed for each analytical determination; (ii) application of HPLC as an alternative to traditional LC, carried with manually packed glass columns, thus simplifying the separation step. Full article
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