A non-invasive, sensor-based approach to exploit the autofluorescence of saffron (Crocus sativus L.) for on-site evaluation of aging.

So far, compliance with ISO 3632 standard specifications for top-quality saffron guarantees good agricultural and post-harvest production practices. Tracking early-stage oxidation remains challenging. Our study aims to address this issue by exploring the visible, fluorescence, and near-infrared spectra of category I saffron. Using a multi-spectral sensor, we tested fresh and artificially aged saffron in powder form. High autofluorescence intensities at 600-700 nm allowed calibration for the 'content of aged saffron'. Samples with minimum coloring strength (200-220 units) were classified as 70% aged, while those exceeding maximum aroma strength (50 units) as 100% aged. Consistent patterns across origin, age, and processing history indicated potential for objectively assessing early-oxidation markers. Further analyses uncovered multiple contributing fluorophores, including cis-apocarotenoids, correlated with FTIR-based aging markers. Our findings underscore that sensing autofluorescence of traded saffron presents an innovative quality diagnostic approach, paving new research pathways for assessing the remaining shelf-life along its supply chain.

Greek PDO saffron authentication studies using species specific molecular markers.

Saffron, the spice produced from the red stigmas of the flower of Crocus sativus L. is a frequent target of fraud and mislabeling practices that cannot be fully traced using the ISO 3632 trade standard specifications and test methods. A molecular approach is proposed herein as a promising branding strategy for the authentication of highly esteemed saffron brands such as the Greek Protected Designation of Origin (PDO) "Krokos Kozanis". Specific ISSR (inter-simple sequence repeat) markers were used to assess for the first time, the within species variability of several populations of C. sativus L. from the cultivation area of "Krokos Kozanis" as well as the potential differences with the band pattern produced by other Crocus species. Then, species-specific markers were developed taking advantage of an advanced molecular technique such as the HRM analysis coupled with universal DNA barcoding regions (trnL) (Bar-HRM) and applied to saffron admixtures with some of the most common plant adulterants (Calendula officinalis, Carthamus tinctorius, Gardenia jasminoides, Zea mays and Curcuma longa). The sensitivity of the procedure was tested for turmeric as a case study whereas HPLC-fluorescence determination of secondary metabolites was also employed for comparison. The overall results indicated that the Bar-HRM approach is quite effective in terms of specificity and sensitivity. Its effectiveness regarding the detection of turmeric was comparable to that of a conventional HPLC method (0.5% vs 1.0%, w/w). Yet, the proposed DNA-based method is much faster, cost-effective and can be used even by non-geneticists, in any laboratory having access to an HRM-capable real-time PCR instrumentation. It can be, thus, regarded as a strong analytical tool in saffron authentication studies.

Ion-pair assisted extraction followed by (1)H NMR determination of biogenic amines in food and biological matrices.

A selective method for the extraction and determination of six biogenic amines (BAs) by NMR is presented. Briefly, BAs are extracted into an organic solvent via the use of an ion pairing agent, followed by a back extraction in D2O in order to acquire the (1)H NMR spectra. The method is studied with respect to the critical experimental parameters and is successfully applied to selected food substrates (dark chocolate, banana, gouda cheese) and biological samples (urine and blood plasma) signifying its potential as an alternative tool for BAs determination. Accurate and precise results are consistently achieved with all matrixes studied. The calculated limits of detection and limits of quantitation were found to be in the ranges 0.05-0.13µg/mL and 0.14-0.38µg/mL, respectively, for biological samples while for food samples they were in the ranges 2.25-6.25µg/g and 6.75-18.7µg/g, respectively.

Consideration of fluorescence properties for the direct determination of erythrosine in saffron in the presence of other synthetic dyes.

Direct selective detection of erythrosine in saffron in the presence of other synthetic dyes considers its fluorescence at 532 nm excitation/548 nm emission. Saffron pre-treatment was according to the ISO 3632-2 trade standard test methods. On account of calculated quantum yield values, none of the yellow dyes is expected to interfere. Among red ones, reservations about allura red AC, azorubine and red 2G were not verified by experimentation, signifying excellent method specificity. Detection and quantification limits (0.56 and 1.70 nM) were of the same magnitude as those reported in the literature after chromatographic separation of erythrosine. The percentage recovery from spiked saffron samples ranging from 63 to 141 was acceptable for residue levels in foods. The matrix effect from crocins (saffron pigments) was evidenced only at a lower spiking level (0.02 mg kg(-1)). The minimum required performance limit (MRPL) was 0.04 mg kg(-1), indicating that the method is appropriate for determining traces of erythrosine in saffron. The approach offers improved sensitivity (by three orders of magnitude) and specificity than the direct spectrophotometric detection of certain synthetic dyes in saffron and deserves attention by the ISO Technical Committee for 'Herbs, culinary spices and condiments'.

Screening method for the detection of artificial colours in saffron using derivative UV-Vis spectrometry after precipitation of crocetin.

A screening method for the detection of artificial colours (naphthol yellow, tartrazine, quinoline yellow, Sunset yellow, Allura red, amaranth, azorubine, Ponceau 4R and Red 2G) in saffron is described. The method involves removal of crocins by precipitation of crocetin (pH 0.1, 90 degrees C) before adsorption of the artificial colours on polyamide SPE cartridges (pH 2). After washing with methanol, acetone and methanol, elution was done with a methanol:ammonia solution (95:5 v/v), and detection was performed by derivative spectrometry. Sample pretreatment changes the UV-Vis saffron extract profile in such a way that second derivative spectra can be used to identify the presence of added colours. Erythrosine, which was found to be pH dependent, could not be detected under the above conditions. The lowest detectable amount for each colour was strongly dependent on chemical structure. The recovery of carminic acid was very low possibly due to irreversible retention on the polyamide. This procedure can replace the current ISO TLC method (2003) and be used alternatively or in combination with HPLC procedures adopted in the same standard.