Advances in vegetable oil authentication by DNA-based markers

Elemental profile of wheat in the las vegas market: Geographic origin discrimination and probabilistic health risk assessment

This study investigates concentrations of toxic and potentially toxic elements (PTEs) in organic and conventional wheat flour and grains marketed in Las Vegas. Geographic origins of the samples were evaluated using Linear Discriminant Analysis (LDA). Monte Carlo Simulation technique was also employed to evaluate non-carcinogenic risk in four life stages. Concentrations of Al, As, Cd, Co, Cr, Cu, Fe, Mn, Mo, Ni, Pb, Se, Sr, and Zn were determined using inductively coupled plasma mass spectrometry (ICP-MS) following hot block-assisted digestion. Obtained results showed non-significant differences in contents of toxic and PTEs between conventional and organic wheat grains/flour. Using LDA, metal (loid)s were found to be indicative of geographical origin. The LDA produced a total correct classification rate of 95.8% and 100% for US and West Pacific Region samples, respectively. The results of the present study indicate that the estimated non-carcinogenic risk associated with toxic element intakes across the four life stages were far lower than the threshold value (Target Hazard Quotient (THQ) > 1). However, the probability of exceeding the threshold value for Mn is approximately 32% in children aged between 5 and 8 years. The findings of this study can aid in understanding dietary Mn exposure in children in Las Vegas.

A review on the identification of transgenic oilseeds and oils

Transgenic technology can increase the quantity and quality of vegetable oils worldwide. However, people are skeptical about the safety of transgenic oil-bearing crops and the oils they produce. In order to protect consumers' rights and avoid transgenic oils being adulterated or labeled as nontransgenic oils, the transgenic detection technology of oilseeds and oils needs careful consideration. This paper first summarized the current research status of transgenic technologies implemented at oil-bearing crops. Then, an inspection process was proposed to detect a large number of samples to be the subject rapidly, and various inspection strategies for transgenic oilseeds and oils were summarized according to the process sequence. The detection indicators included oil content, fatty acid, triglyceride, tocopherol, and nucleic acid. The detection technologies involved chromatography, spectroscopy, nuclear magnetic resonance, and polymerase chain reaction. It is hoped that this article can provide crucial technical reference and support for staff engaging in the supervision of transgenic food and for researchers developing fast and efficient monitoring methods in the future.

Detection of Hazelnut and Almond Adulteration in Olive Oil: An Approach by qPCR

Virgin olive oil (VOO), characterized by its unique aroma, flavor, and health benefits, is subject to adulteration with the addition of oils obtained from other edible species. The consumption of adulterated olive oil with nut species, such as hazelnut or almond, leads to health and safety issues for consumers, due to their high allergenic potential. To detect almond and hazelnut in olive oil, several amplification systems have been analyzed by qPCR assay with a SYBR Green post-PCR melting curve analysis. The systems selected were Cora1F2/R2 and Madl, targeting the genes coding the allergenic protein Cor a 1 (hazelnut) and Pru av 1 (almond), respectively. These primers revealed adequate specificity for each of the targeted species. In addition, the result obtained demonstrated that this methodology can be used to detect olive oil adulteration with up to 5% of hazelnut or almond oil by a single qPCR assay, and with a level as low as 2.5% by a nested-qPCR assay. Thus, the present research has shown that the SYBR-based qPCR assay can be a rapid, precise, and accurate method to detect adulteration in olive oil.

Authentication of Argan (Argania spinosa L.) Oil Using Novel DNA-Based Approaches: Detection of Olive and Soybean Oils as Potential Adulterants

Argan oil is a traditional product obtained from the fruits of the argan tree (Argania spinosa L.), which is endemic only to Morocco. It is commercialized worldwide as cosmetic and food-grade argan oil, attaining very high prices in the international market. Therefore, argan oil is very prone to adulteration with cheaper vegetable oils. The present work aims at developing novel real-time PCR approaches to detect olive and soybean oils as potential adulterants, as well as ascertain the presence of argan oil. The ITS region, matK and lectin genes were the targeted markers, allowing to detect argan, olive and soybean DNA down to 0.01 pg, 0.1 pg and 3.2 pg, respectively, with real-time PCR. Moreover, to propose practical quantitative methods, two calibrant models were developed using the normalized ΔCq method to estimate potential adulterations of argan oil with olive or soybean oils. The results allowed for the detection and quantification of olive and soybean oils within 50–1% and 25–1%, respectively, both in argan oil. Both approaches provided acceptable performance parameters and accurate determinations, as proven by their applicability to blind mixtures. Herein, new qualitative and quantitative PCR assays are proposed for the first time as reliable and high-throughput tools to authenticate and valorize argan oil.

Adulteration detection of essence in sesame oil based on headspace gas chromatography-ion mobility spectrometry

Sesame oil is a traditional and delicious edible oil in China and Southeast Asia with a high price. However, sesame oil essence was often illegally added to cheaper edible oils to counterfeit sesame oil. In this study, a rapid and accurate headspace gas chromatography-ion mobility spectrometry (HS-GC-IMS) method was proposed to detect the counterfeit sesame oil where the other cheap oils were adulterated with essence. Combined with chemometric methods including principal component analysis (PCA), orthogonal partial least squares discriminant analysis (OPLS-DA) and random forest (RF), authentic and counterfeit sesame oils adulterated with sesame essence (0.5%, w/w) were easily separated into two groups. More importantly, 2-methylbutanoic acid, 2-furfurylthiol, methylpyrazine, methional, and 2,5-dimethylpyrazine were found to be markers of sesame essence, which were used to directly identify the sesame essence. The determination of volatile compounds based on HS-GC-IMS was proven to be an effective method for adulteration detection of essence in sesame oil.

Evaluation of simple sequence repeats (SSR) and single nucleotide polymorphism (SNP)-based methods in olive varieties from the Northwest of Spain and potential for miniaturization

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SSR- and SNP-based methods were evaluated for the identification of olive varieties.

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SNP identification was performed for the first time for two autochthonous varieties.

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The potential for future miniaturization of the genotyping methods was evaluated.

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Allele-specific PCR provided the best results for the tested olive varieties.

Miniaturization of DNA-based techniques can bring interesting advantages for food analysis, such as portability of complex analytical procedures. In the olive oil industry, miniaturization can be particularly interesting for authenticity and traceability applications, through in situ control of raw materials before production and/or the final products. However, variety identification is challenging, and implementation on miniaturized settings must be carefully evaluated, starting from the selected analytical approach. In this work, SSR- and SNP-based genotyping strategies were investigated for the identification and differentiation of two olive varieties from the Northwest of Spain. For the selected SNPs two genotyping methods were tested: real-time allele-specific PCR and high resolution melting analysis. These methods were compared and evaluated regarding their potential for integration in a microfluidic device. Both SNP-based methods proved to be successful for identification of the selected varieties, however real-time allele-specific PCR was the one that achieved the best results when analyzing mixtures, allowing the identification of both monovarietal samples and mixtures of the varieties tested with up to 25%.

Oil palm in the 2020s and beyond: challenges and solutions

BACKGROUND

Oil palm, Elaeis guineensis, is by far the most important global oil crop, supplying about 40% of all traded vegetable oil. Palm oils are key dietary components consumed daily by over three billion people, mostly in Asia, and also have a wide range of important non-food uses including in cleansing and sanitizing products.

MAIN BODY

Oil palm is a perennial crop with a > 25-year life cycle and an exceptionally low land footprint compared to annual oilseed crops. Oil palm crops globally produce an annual 81 million tonnes (Mt) of oil from about 19 million hectares (Mha). In contrast, the second and third largest vegetable oil crops, soybean and rapeseed, yield a combined 84 Mt oil but occupy over 163 Mha of increasingly scarce arable land. The oil palm crop system faces many challenges in the 2020s. These include increasing incidence of new and existing pests/diseases and a general lack of climatic resilience, especially relating to elevated temperatures and increasingly erratic rainfall patterns, plus downstream issues relating to supply chains and consumer sentiment. This review surveys the oil palm sector in the 2020s and beyond, its major challenges and options for future progress.

CONCLUSIONS

Oil palm crop production faces many future challenges, including emerging threats from climate change and pests and diseases. The inevitability of climate change requires more effective international collaboration for its reduction. New breeding and management approaches are providing the promise of improvements, such as much higher yielding varieties, improved oil profiles, enhanced disease resistance, and greater climatic resilience.

Geographical origin discrimination of "Ntopia" olive oil cultivar from Ionian islands using volatile compounds analysis and computational statistics

The aim of the present study was to characterize the aroma profile of olive oil of the "Ntopia" (local) cultivar from the Ionian islands (Zakynthos, Kefalonia, Leukada, and Kerkyra) (Greece), and investigate whether specific volatile compounds could be considered as indicators of olive oil geographical origin, using computational statistics. In this context, 137 olive oil samples were subjected to headspace solid phase microextraction coupled to gas chromatography/mass spectrometry using the internal standard method. Computational statistics on the semi-quantitative data of olive oil samples, as rapid machine learning algorithms, showed that specific volatile compounds could be used as indicators of geographical origin of olive oil of the "Ntopia" cultivar, among the four main Ionian islands. Volatile compounds such as ethanol, pentanal, 2,4-dimethylheptane, 3,7-dimethyl-1,3,6-octatriene (E), 2,5-dimethylnonane, 1-hexanol, 6-methyl-5-hepten-2-one, octanal, dl-Limonene, acetic acid hexyl ester and dodecane could aid to the geographical origin discrimination of "Ntopia" olive oil cultivar when two (Zakynthos and Kefalonia) or four (Zakynthos, Kefalonia, Leukada and Kerkyra) Ionian islands are subjected to statistical analysis. The discrimination rate using the cross-validation method was 100% and 85.7%, respectively. These results were further evaluated using training and holdout partitions, during which a comparable classification rate was obtained.

SUPPLEMENTARY INFORMATION

The online version contains supplementary material available at 10.1007/s00217-021-03863-2.

Microsatellite Markers in Olives (Olea europaea L.): Utility in the Cataloging of Germplasm, Food Authenticity and Traceability Studies

The olive fruit, a symbol of Mediterranean diets, is a rich source of antioxidants and oleic acid (55–83%). Olive genetic resources, including cultivated olives (cultivars), wild olives as well as related subspecies, are distributed widely across the Mediterranean region and other countries. Certain cultivars have a high commercial demand and economical value due to the differentiating organoleptic characteristics. This might result in economically motivated fraudulent practices and adulteration. Hence, tools to ensure the authenticity of constituent olive cultivars are crucial, and this can be achieved accurately through DNA-based methods. The present review outlines the applications of microsatellite markers, one of the most extensively used types of molecular markers in olive species, particularly referring to the use of these DNA-based markers in cataloging the vast olive germplasm, leading to identification and authentication of the cultivars. Emphasis has been given on the need to adopt a uniform platform where global molecular information pertaining to the details of available markers, cultivar-specific genotyping profiles (their synonyms or homonyms) and the comparative profiles of oil and reference leaf samples is accessible to researchers. The challenges of working with microsatellite markers and efforts underway, mainly advancements in genotyping methods which can be effectively incorporated in olive oil varietal testing, are also provided. Such efforts will pave the way for the development of more robust microsatellite marker-based olive agri-food authentication platforms.

Evaluation of DNA extraction methods for molecular traceability in cold pressed, solvent extracted and refined groundnut oils

Groundnut oil (GNO)/peanut oil is one of the agro-food products with great economic value and hence an attractive target for adulteration and mislabeling. Simple Sequence Repeats (SSR) are markers of choice for DNA fingerprinting studies as they exhibit high polymorphism due to variable number of repeats. Hence, this study was designed to evaluate and optimize a method for DNA isolation from groundnut oil and study the possibility of using the isolated DNA for molecular traceability using SSR markers. Four methods to isolate DNA from groundnut oil were evaluated. All the four methods were modified CTAB protocols, but differed in procedures for extraction, buffer compositions, amount of oil used and DNA carriers. For molecular traceability of oils, extraction and recovery of DNA from edible oil is a key step, especially in refined oils. A method that employed DNA enrichment prior to extraction with CTAB buffer yielded amplifiable DNA from cold pressed GNO, crude hexane extracted GNO and refined GNO. The optimized method for isolation of DNA from groundnut oil is simple, efficient, less costly and reproducible when compared to chromatography and spectroscopy based techniques.

An optimized procedure for detection of genetically modified DNA in refined vegetable oils

In this study, the amplifiable DNA from refined vegetable oils was isolated by using commercial DNA extraction kits based on the CTAB method in combination with nucleic acid enrichment, and then the presence of genetically modified (GM) soybean and maize DNA in the oils was traced by PCR. The results showed that the duration and intensity of heating had no significant effect on the DNA stability and concentration in oils for a short period, suggesting that DNA in oils could be stably reserved for a certain time, thus making it possible to trace down refined vegetable oils reliably and effectively. The results provided a set of primers suitable for systematic GM oil detection. More importantly, this study made an important contribution to the economical and reliable detection of GM vegetable oils regarding food authenticity issues.

The Application of Chemometrics to Volatile Compound Analysis for the Recognition of Specific Markers for Cultivar Differentiation of Greek Virgin Olive Oil Samples

In the present study, volatile compound analysis of olive oil samples belonging to ten Greek cultivars was carried out. A total of 167 olive oil samples collected from two consecutive harvest years were analyzed by Head Space-Solid Phase Microextraction-Gas Chromatography/Mass Spectrometry (HS-SPME-GC/MS). Volatile compound data were combined with chemometric methods (Multivariate Analysis of Variance (MANOVA) and Linear Discriminant Analysis (LDA)) with the aim not only to differentiate olive oils but also to identify characteristic volatile compounds that would enable differentiation of botanical origin (marker compounds). The application of Stepwise LDA (SLDA) effectively reduced the large number of statistically significant volatile compounds involved in the differentiation process, and thus, led to a set of parameters, the majority of which belong to compounds that are highly dependent on variety. In addition, the use of these marker compounds resulted in an increased correct classification rate (85.6%) using the cross-validation method indicating the validity of the model developed despite the use of a large number of dependent variables (cultivars).

Development of nucleic acid isolation by non-silica-based nanoparticles and real-time PCR kit for edible vegetable oil traceability

For efficient extraction of amplifiable DNA from edible vegetable oils, we developed a novel DNA extraction approach based on the non-silica-based dipolar nanocomposites. The nanoparticle comprises a hydrophilic polymethyl methacrylate core with abundant capillaries, hydrophilic vesicles decorated with molecules having DNA affinity and a coating hydrophobic polystyrene layer. The nanoparticles are soluble in oil, adsorb the DNA from the aqueous phase and gave a high DNA recovery ratio. All DNA extracts from fully refined vegetable oil soybean, peanut, rapeseed, and cottonseed oils, including their blends, were sufficiently pure to be amplified by real-time PCR targeting the chloroplast ribulose-1,5-bisphosphate gene (rbcL), therefore, the species of origin and their ratios in mixed vegetable oils blended from two or three oil-species could be determined. These results indicate that the novel DNA isolation and real-time PCR kit is a simple, sensitive and efficient tool for the species identification and traceability in refined vegetable oils.

Discovery of food identity markers by metabolomics and machine learning technology

Verification of food authenticity establishes consumer trust in food ingredients and components of processed food. Next to genetic or protein markers, chemicals are unique identifiers of food components. Non-targeted metabolomics is ideally suited to screen food markers when coupled to efficient data analysis. This study explored feasibility of random forest (RF) machine learning, specifically its inherent feature extraction for non-targeted metabolic marker discovery. The distinction of chia, linseed, and sesame that have gained attention as “superfoods” served as test case. Chemical fractions of non-processed seeds and of wheat cookies with seed ingredients were profiled. RF technology classified original seeds unambiguously but appeared overdesigned for material with unique secondary metabolites, like sesamol or rosmarinic acid in the Lamiaceae, chia. Most unique metabolites were diluted or lost during cookie production but RF technology classified the presence of the seed ingredients in cookies with 6.7% overall error and revealed food processing markers, like 4-hydroxybenzaldehyde for chia and succinic acid monomethylester for linseed additions. RF based feature extraction was adequate for difficult classifications but marker selection should not be without human supervision. Combination with alternative data analysis technologies is advised and further testing of a wide range of seeds and food processing methods.

Development of conventional PCR and real-time PCR assays to discriminate the origins of Chinese pepper oil and herbal materials from Zanthoxylum

BACKGROUND

To ensure the safety, quality and therapeutic efficacy of processed foods and herbal medicines, it is important to identify and discriminate economically motivated adulterants. Zanthoxylum schinifolium is sold at a higher price than other Zanthoxylum species and is frequently adulterated with closely related Zanthoxylum species because of its high demand as a Korean food ingredient and medicinal material in markets. In addition, the pericarps of three Zanthoxylum species (Z. schinifolium, Z. bungeanum and Z. piperitum) are defined as herbal medicine Zanthoxyli Pericarpium in Korean pharmacopoeias, but not Z. piperitum in Chinese pharmacopoeias. Further confusion arises in the morphological similarity between Z. armatum (adulterant) and Z. bungeanum. Therefore, the aim of this study was to develop a sequence characterized amplified region (SCAR) marker for discrimination of four Zanthoxylum species.

RESULTS

With the goal of developing rapid and reliable tools for genetic discrimination of authentic Zanthoxyli Pericarpium, we designed species-specific SCAR markers, based on ITS2 sequences, that generate amplicons of less than 200 bp. Using these markers, we established both conventional and real-time PCR assay methods capable of differentiating samples at the species level. We validated the ability of SCAR markers to authenticate edible oil and herbal medicine, and confirmed that some herbal medicines contaminated with Z. armatum are being distributed as Zanthoxyli Pericarpium in Korean and Chinese markets.

CONCLUSIONS

The SCAR markers and PCR methods described represent powerful tools for protecting against adulteration and ensuring standardization of processed foods and herbal medicine. © 2018 The Authors. Journal of the Science of Food and Agriculture published by John Wiley & Sons Ltd on behalf of Society of Chemical Industry.

Recent developments in olive (Olea europaea L.) genetics and genomics: applications in taxonomy, varietal identification, traceability and breeding

The latest results in DNA markers application and genomic studies in olive. Olive (Olea europaea L.) is among the most ancient tree crops worldwide and the source of oil beneficial for human health. Despite this, few data on olive genetics are available in comparison with other cultivated plant species. Molecular information is mainly linked to molecular markers and their application to the study of DNA variation in the Olea europaea complex. In terms of genomic research, efforts have been made in sequencing, heralding the era of olive genomic. The present paper represents an update of a previous review work published in this journal in 2011. The review is again mainly focused on DNA markers, whose application still constitutes a relevant percentage of the most recently published researches. Since the olive genomic era has recently started, the latest results in this field are also being discussed.

Evolution and perspectives of cultivar identification and traceability from tree to oil and table olives by means of DNA markers

In recent years, an increasing number of typicality marks has been awarded to high-quality olive oils produced from local cultivars. In this case, quality control requires effective varietal checks of the starting materials. Moreover, accurate cultivar identification is essential in vegetative-propagated plants distributed by nurseries and is a pre-requisite to register new cultivars. Food genomics provides many tools for cultivar identification and traceability from tree to oil and table olives. The results of the application of different classes of DNA markers to olive with the purpose of checking cultivar identity and variability of plant material are extensively discussed in this review, with special regard to repeatability issues and polymorphism degree. The characterization of olive germplasm from all countries of the Mediterranean basin and from less studied geographical areas is described and innovative high-throughput molecular tools to manage reference collections are reviewed. Then the transferability of DNA markers to processed products - virgin olive oils and table olives - is overviewed to point out strengths and weaknesses, with special regard to (i) the influence of processing steps and storage time on the quantity and quality of residual DNA, (ii) recent advances to overcome the bottleneck of DNA extraction from processed products, (iii) factors affecting whole comparability of DNA profiles between fresh plant materials and end-products, (iv) drawbacks in the analysis of multi-cultivar versus single-cultivar end-products and (v) the potential of quantitative polymerase chain reaction (PCR)-based techniques. © 2016 Society of Chemical Industry.

Cultivar origin and admixture detection in Turkish olive oils by SNP-based CAPS assays

The aim of this study was to establish a DNA-based identification key to ascertain the cultivar origin of Turkish monovarietal olive oils. To reach this aim, we sequenced short fragments from five olive genes for SNP (single nucleotide polymorphism) identification and developed CAPS (cleaved amplified polymorphic DNA) assays for SNPs that alter restriction enzyme recognition motifs. When applied on the oils of 17 olive cultivars, a maximum of five CAPS assays were necessary to discriminate the varietal origin of the samples. We also tested the efficiency and limit of our approach for detecting olive oil admixtures. As a result of the analysis, we were able to detect admixing down to a limit of 20%. The SNP-based CAPS assays developed in this work can be used for testing and verification of the authenticity of Turkish monovarietal olive oils, for olive tree certification, and in germplasm characterization and preservation studies.

Advanced detection methods for traceability of origin and authenticity of olive oils

This review focuses on the advances in the sensing and identification of adulteration of olive oil, including optical sensing, chromatography, nuclear magnetic resonance, and DNA-based methods.

Barcoding melting curve analysis for rapid, sensitive, and discriminating authentication of saffron (Crocus sativus L.) from its adulterants

Saffron (Crocus sativus L.) is one of the most important and expensive medicinal spice products in the world. Because of its high market value and premium price, saffron is often adulterated through the incorporation of other materials, such as Carthamus tinctorius L. and Calendula officinalis L. flowers, Hemerocallis L. petals, Daucus carota L. fleshy root, Curcuma longa L. rhizomes, Zea may L., and Nelumbo nucifera Gaertn. stigmas. To develop a straightforward, nonsequencing method for rapid, sensitive, and discriminating detection of these adulterants in traded saffron, we report here the application of a barcoding melting curve analysis method (Bar-MCA) that uses the universal chloroplast plant DNA barcoding region trnH-psbA to identify adulterants. When amplified at DNA concentrations and annealing temperatures optimized for the curve analysis, peaks were formed at specific locations for saffron (81.92°C) and the adulterants: D. carota (81.60°C), C. tinctorius (80.10°C), C. officinalis (79.92°C), Dendranthema morifolium (Ramat.) Tzvel. (79.62°C), N. nucifera (80.58°C), Hemerocallis fulva (L.) L. (84.78°C), and Z. mays (84.33°C). The constructed melting curves for saffron and its adulterants have significantly different peak locations or shapes. In conclusion, Bar-MCA could be a faster and more cost-effective method to authenticate saffron and detect its adulterants.

Quantitative detection of soybean in meat products by a TaqMan real-time PCR assay

In the present work, we propose a normalised real-time quantitative PCR assay to determine the addition of soybean to meat products. The method proved to be a powerful tool for the quantification of soybean protein (dry basis) in the range of 0.01% to 6%, being successfully in-house validated. Its application was effective in the analysis of several meat products, indicating 2% of non-compliance with the food allergen labelling legislation, and some inconsistencies when comparing the declared with estimated amounts of soybean. This work highlights the importance of efficient tools to assess labelling statements of meat products, avoiding fraudulent practices.

Development of a method to recovery and amplification DNA by real-time PCR from commercial vegetable oils

This study describes the design of a suitable DNA isolation method from commercial vegetable oils for the application of DNA markers for food safety and traceability. Firstly, a comparative study was made of eight methods for the recovery of high quality DNA from olive, sunflower and palm oils, and a CTAB-based method was selected. In order to optimize this method, the effect of the organic compounds and several components in the lysis buffer and the lysis and precipitation time were evaluated. For the purpose of overcoming the limitations detected in spectrophotometric and PCR DNA yield evaluations, the performance of the extraction protocols during the optimization processes was evaluated using qPCR. The suggested DNA extraction optimized is less time consuming than other conventional DNA extraction methods, uses a reduced oil volume and is cheaper than available commercial kits. Additionally, the applicability of this method has been successfully assayed in ten commercial vegetable oils and derivatives.

Barcode DNA high-resolution melting (Bar-HRM) analysis as a novel close-tubed and accurate tool for olive oil forensic use

BACKGROUND

The adulteration of high-priced olive oil with low-cost oils and the fraudulent labelling of oil products make the identification and traceability of vegetable oil species in the food chain very important. This paper describes a high-resolution melting analysis-based method using chloroplast barcoding regions as target (Bar-HRM) to obtain barcoding information for the major vegetable oil species and to quantitatively identify the botanical origin of plant oils. The detection of adulteration of olive oil with canola oil was used as a case study.

RESULTS

The proposed method was capable of distinguishing among different vegetable oil species and detecting a level of 1% (w/w) of canola oil in olive oil.

CONCLUSION

Bar-HRM analysis is a more accurate, faster and less costly alternative method to authenticate vegetable oils, including olive oil, and to detect mixtures of oils.