Toward the Non-Targeted Detection of Adulterated Virgin Olive Oil with Edible Oils via FTIR Spectroscopy & Chemometrics: Research Methodology Trends, Gaps and Future Perspectives

Fourier-Transform mid-infrared (FTIR) spectroscopy offers a strong candidate screening tool for rapid, non-destructive and early detection of unauthorized virgin olive oil blends with other edible oils. Potential applications to the official anti-fraud control are supported by dozens of research articles with a “proof-of-concept” study approach through different chemometric workflows for comprehensive spectral analysis. It may also assist non-targeted authenticity testing, an emerging goal for modern food fraud inspection systems. Hence, FTIR-based methods need to be standardized and validated to be accepted by the olive industry and official regulators. Thus far, several literature reviews evaluated the competence of FTIR standalone or compared with other vibrational techniques only in view of the chemometric methodology, regardless of the inherent characteristics of the product spectra or the application scope. Regarding authenticity testing, every step of the methodology workflow, and not only the post-acquisition steps, need thorough validation. In this context, the present review investigates the progress in the research methodology on FTIR-based detection of virgin olive oil adulteration over a period of more than 25 years with the aim to capture the trends, identify gaps or misuses in the existing literature and highlight intriguing topics for future studies. An extensive search in Scopus, Web of Science and Google Scholar, combined with bibliometric analysis, helped to extract qualitative and quantitative information from publication sources. Our findings verified that intercomparison of literature results is often impossible; sampling design, FTIR spectral acquisition and performance evaluation are critical methodological issues that need more specific guidance and criteria for application to product authenticity testing

Phenolic acids as natural inhibitors of oxidation evaluation of activity - prospects of exploitation in functional foods

Structure-radical scavenging activity relationships (SAR) among a great number of acid phenols and related compounds were studied using the Crocin Bleaching Assay (CBA) and/or other assays (DPPH•, ORAC, lipid oxidation), where necessary. The focus was on the activity of various hydroxybenzoic, hydroxyphenylacetic, hydroxyphenylpropanoic and hydroxycinnamic acids. Prior to estimation of antioxidant activity, the CBA protocol was in-house validated taking into account that reliability of SAR evaluation is often subjected to method limitations (e.g. ease and reproducibility). Consistency of experimental findings with Physical Organic Chemistry principles was also taken into account. A step by step chromatographic (HPLC, GC) and spectrophotometric examination of method performance with regard to probe, azo-initiator and test compound characteristics showed that: a) any authentic commercial saffron (origin, grade) can be used for probe preparation as long as certain precautions are taken (removal of interference, adjustement of crocin concentration, short-time storage of probe solution), b) AAPH-derived radical generation conditions such as preheatment are not critical, c) any phenolic compound (AH) meeting the criterion Log PAH vanillic acid). However, the activity order between the respective catechol acid derivatives strongly varied depending on the assay conditions. Homoprotocatechuic acid (-CH2COOH) was most active towards DPPH• in methanol while protocatechuic acid (–COOH) was most active under CBA conditions. CBA findings were meaningful when the acidity of –COOH and 4-OH groups were taken into account. Under all assay conditions, extended conjugation to the side carbon chain of 4- hydroxycinnamic acids was essential for the rapid scavenging of free radicals. Thus, caffeic and ferulic acids were considerably more active than their dihydrocounterparts. Apart from a better stabilization of the phenoxy radicals through resonance structures, the strong acidity of these compounds may contribute to their potency. The results indicate that CBA is suitable for evaluation of SARs among closely related compound bearing small structural differences. The importance of simple plant-derived acid phenols as efficient radical scavengers under conditions that imitate physiological ones is also highlightened. Investigation of the role of the – COOH group showed that reduction to –CHO or esterification with short-chain alcohols may render acid phenols even more potent towards peroxyl radicals. The greater antiradical activity found for some acid derivatives such as alkyl gallates (methyl- and propyl-gallate) and hydroxybenzaldehydes (vanillin, syringic aldehyde), also less hydrophilic than the respective acids, is promising for further studies and exploitation of natural sources

Detection of ternary mixtures of virgin olive oil with canola, hazelnut or safflower oils via non-targeted ATR-FTIR fingerprinting and chemometrics

Detection of extra virgin olive oil (EVOO) adulteration with ternary mixtures of undeclared foreign oils has rarely been reported in literature. The aim of the study was to develop a fit-for-purpose and highly sensitive non-targeted fingerprinting method via ATR-FTIR spectroscopy and qualitative modelling to detect ternary blends of a cheap unsaturated oil (safflower), two high in oleic acid oils (canola and hazelnut oils) at a standard adulteration level (20% v/v). An in-house spectral library for authentic EVOOs was exploited as reference data source. The 2nd derivative ATR-FTIR spectra were carefully explored for outliers throughout the multivariate calibration procedure using the Partial Least Squares Projection to Latent Structures-Discriminant Analysis (PLS-DA) and the Soft Independent Modelling of Class Analogy (SIMCA) methods. Stepwise external validation of the resulting models signified 100% sensitivity in detecting challenging cases of adulteration, i.e. with 5% canola and 15% hazelnut oils. Taken the natural variability in composition of authentic EVOOs from different producing regions and harvest year and the complexity of the studied mixtures, the overall predictive power of every resulting model was found quite high, >92%. A prospective for expanding application at lower adulteration levels i.e. 10% v/v was also evidenced.O. Ozdikicierler thanks the TUBITAK 2219 Post-Doctoral Programme (1059B191701190) for funding his stay at AUTh.TUBITAK 2219 Post-Doctoral Programme [1059B191701190

Toward the Non-Targeted Detection of Adulterated Virgin Olive Oil with Edible Oils via FTIR Spectroscopy & Chemometrics: Research Methodology Trends, Gaps and Future Perspectives

Fourier-Transform mid-infrared (FTIR) spectroscopy offers a strong candidate screening tool for rapid, non-destructive and early detection of unauthorized virgin olive oil blends with other edible oils. Potential applications to the official anti-fraud control are supported by dozens of research articles with a “proof-of-concept” study approach through different chemometric workflows for comprehensive spectral analysis. It may also assist non-targeted authenticity testing, an emerging goal for modern food fraud inspection systems. Hence, FTIR-based methods need to be standardized and validated to be accepted by the olive industry and official regulators. Thus far, several literature reviews evaluated the competence of FTIR standalone or compared with other vibrational techniques only in view of the chemometric methodology, regardless of the inherent characteristics of the product spectra or the application scope. Regarding authenticity testing, every step of the methodology workflow, and not only the post-acquisition steps, need thorough validation. In this context, the present review investigates the progress in the research methodology on FTIR-based detection of virgin olive oil adulteration over a period of more than 25 years with the aim to capture the trends, identify gaps or misuses in the existing literature and highlight intriguing topics for future studies. An extensive search in Scopus, Web of Science and Google Scholar, combined with bibliometric analysis, helped to extract qualitative and quantitative information from publication sources. Our findings verified that intercomparison of literature results is often impossible; sampling design, FTIR spectral acquisition and performance evaluation are critical methodological issues that need more specific guidance and criteria for application to product authenticity testing

Enhanced Bioaccessibility of Crocetin Sugar Esters from Saffron in Infusions Rich in Natural Phenolic Antioxidants

The present study aims to examine whether and to what extent the bioaccessibility of the major saffron apocarotenoids, namely crocetin sugar esters (CRTSEs), is affected by the presence of strong water-soluble antioxidants, ingredients of the herbs found in commercial tea blends with saffron. An in vitro digestion model was applied to infusions from these products to investigate the possible changes. All of the studied infusions were rich in total phenols (9.9–22.5 mg caffeic acid equivalents/100 mg dry infusion) and presented strong DPPH radical scavenging activity regardless of the composition of the corresponding herbal blends. RP-HPLC-DAD and LC-MS analysis enabled the grouping of the infusions into hydroxycinnamic acid-rich and in flavan-3-ol-rich ones. CRTSEs in herbal tea infusions were found to be significantly more bioaccessible (66.3%–88.6%) than those in the reference saffron infusion (60.9%). The positive role of strong phenolic antioxidants (caffeic acid, rosmarinic acid) on the stability of CRTSEs was also evidenced in model binary mixtures. On the contrary, cinnamic acid, exerting no antioxidant activity, did not have such an effect. Our findings suggest that strong radical scavengers may protect the crocetin sugar esters from oxidation during digestion when present in excess

The Potential of Tree Fruit Stone and Seed Wastes in Greece as Sources of Bioactive Ingredients

The inedible part (stones, husks, kernels, seeds) of the tree fruits that are currently processed in various regions of Greece constitutes a huge portion of the fruit processing solid waste that remains underexploited. In this review, the existing scientific background for the composition and content of fruit stone and seed in bioactive ingredients is highlighted for olives, stone fruits and citrus fruits that represent the economically most important tree crop products of the country. The content of bioactive compounds may vary considerably depending on the quality of the raw material and the treatment during processing. However, both the hydrophilic and the lipophilic fractions of the seeds contain significant amounts of the primary and the secondary plant metabolites. Among them, phytosterols and several types of polyphenols, but also squalene, tocopherols and some other terpenoids with a unique structure are of particular importance for the utilization and valorization of stones and seeds. Official and scholar records about the current management practices are also presented to highlight the dynamics of the Greek fruit sector. Prospects for the regionalization of fruit seed wastes, in line with EU-promoted Research and Innovation Strategies (RIS) for Smart Specialization are critically discussed