Fluorescence Monitoring Oxidation of Extra Virgin Olive Oil Packed in Different Containers.

'Picual' olive oil was stored in different types of containers for 10 months and monitored via quality parameters. In combination with the mentioned analysis, non-destructive fluorescence spectroscopy was performed combined with multivariate analysis to monitor and quantify oil quality levels. Excitation emission matrices (EMMs) were analyzed using parallel factor analysis (PARAFAC). According to the quality parameters, it was observed that Transparent Crystal (TC) and Opaque Crystal (OC) samples were the ones that deteriorated faster due to their higher exposure to light in comparison with Plastic (P) and Canned (C) samples. In a fast and non-destructive manner, the fluorescence spectroscopy-based prototype successfully monitored the oxidation changes in the EVOOs. Unfolded partial least squares (U-PLS) was used to generate a regression model to quantify quality parameters. Good correlation coefficients were found for the peroxide index, K232 and the oxidative stability index (r2 between 0.90 and 0.94 for cross-validation and validation). For all of that, the results obtained confirmed the ability of fluorescence spectroscopy to monitor the quality of olive oil and EEMs combined with U-PLS can be used to analyze these parameters, eluding the classical methods.

Application of Digital Olfaction for Table Olive Industry.

The International Olive Council (IOC) established that olives must be free of odors, off-flavors, and absent of abnormal ongoing alterations or fermentations. The use of electronic devices could help when classifying defects in a fast, non-destructive, cheap, and environmentally friendly way. For all of that, table olives were evaluated according to IOC regulation in order to classify the defect predominant perceiving (DPP) of the table olives and their intensity. Abnormal fermentation defects of Spanish-style table olives were assessed previously by an IOC-validated tasting panel. 'Zapateria', 'Putrid', and 'Butyric' were the defects found at different concentrations. Different volatile compounds were identified by gas chromatography in altered table olives. The same samples were measured with an electronic nose device (E-nose). E-nose data combined with chemometrics algorithms, such as PCA and PLS-DA, were able to successfully discriminate between healthy and non-healthy table olives, being this last one also separated between the first and second categories. Volatile compounds obtained with gas chromatography could be related to the E-nose measuring and sensory analysis, being capable of matching the different defects with their correspondents' volatile compounds.

Electronic nose application for the discrimination of sterilization treatments applied to Californian-style black olive varieties.

BACKGROUND: Olive oil continues to be the main destination for olives. The production of table olives is increasing. 'Californian-style' processes are among the most frequently employed to produce oxidized olives. Sensory evaluation requires the development of an instrumental detection method that can be used as an adjunct to traditional tasting panels. RESULTS: An electronic nose (E-nose) was used to classify two varieties of olives following exposure to different sterilization. Principal component analysis (PCA) revealed that both varieties had different volatile profiles. Sensory panel evaluations were similar for both. Partial least squares-discriminant analysis (PLS-DA) obtained from the E-nose was able to separate the two varieties and explained 82% of total variance. Moreover, volatile profiles correctly classified olives according to sterilization times recorded up to 121 °C . The only exception was at F0 ≥ 22 min, at which a plot of PCA outcomes failed to differentiate scores. E-nose data showed similar results to those produced from the volatile analysis when grouping samples were sterilized to F0 ≥ 18 min, at the same time distinguishing these samples from those subjected to less intense thermal treatments. A partial least squares (PLS) chemometric approach was evaluated for quantifying important olive quality parameters. With regards to validation parameters, R P 2 pertaining to perceived defect was 0.88, whilst R P 2 pertaining to overall assessment was 0.78. CONCLUSIONS: E-nose offers a fast, inexpensive and non-destructive method for discriminating between varieties and thermal treatments up to a point at which cooking defects are highly similar (from F0  = 18 onwards). © 2021 Society of Chemical Industry.

Characterization of Polyphenol and Volatile Fractions of Californian-Style Black Olives and Innovative Application of E-nose for Acrylamide Determination.

Californian-style black olives require a sterilization treatment that produces a carcinogenic contaminant, acrylamide. Thus, this compound was evaluated in two different olive cultivars using an electronic nose (E-nose). The sterilization intensity had a significant influence on the final phenol concentrations, acrylamide content, and volatile compounds. Increasing the sterilization intensity from 10 to 26 min (F0) reduced the phenol content, but it promoted acrylamide synthesis, leading to a wide range of this toxic substance. The Ester and phenol groups of volatile compounds decreased their content when the sterilization treatment increased; however, aldehyde and other volatile compound groups significantly increased their contents according to the thermal treatments. The compounds 4-ethenyl-pyridine, benzaldehyde, and 2,4-dimethyl-hexane are volatile compounds with unpleasant odours and demonstrated a high amount of influence on the differences found after the application of the thermal treatments. The "Manzanilla Cacereña" variety presented the highest amount of phenolic compounds and the lowest acrylamide content. Finally, it was found that acrylamide content is correlated with volatile compounds, which was determined using multiple linear regression analysis (R2 = 0.9994). Furthermore, the aroma of table olives was analysed using an E-nose, and these results combined with Partial Least Square (PLS) were shown to be an accurate method (range to error ratio (RER) >10 and ratio of performance to deviation (RPD) >2.5) for the indirect quantification of this toxic substance.

E-Nose Discrimination of Abnormal Fermentations in Spanish-Style Green Olives.

Current legislation in Spain indicates that table olives must be free of off-odors and off-flavors and without symptoms of ongoing alteration or abnormal fermentations. In this regard, the International Olive Council (IOC) has developed a protocol for the sensory classification of table olives according to the intensity of the predominantly perceived defect (PPD). An electronic nose (e-nose) was used to assess the abnormal fermentation defects of Spanish-style table olives that were previously classified by a tasting panel according to the IOC protocol, namely zapateria, butyric, putrid, and musty or humidity. When olives with different defects were mixed, the putrid defect had the greatest sensory impact on the others, while the butyric defect had the least sensory dominance. A total of 49 volatile compounds were identified by gas chromatography, and each defect was characterized by a specific profile. The e-nose data were analyzed using principal component analysis (PCA) and partial least square discriminant analysis (PLS-DA). The different defects were clearly separated from each other and from the control treatment, independently of PPD intensity. Moreover, the e-nose differentiated control olives from table olives with combined sensory defects despite the dilution effect resulting from the combination. These results demonstrate that e-nose can be used as an olfactory sensor for the organoleptic classification of table olives and can successfully support the tasting panel.

Industrial Strategies to Reduce Acrylamide Formation in Californian-Style Green Ripe Olives.

Acrylamide, a compound identified as a probable carcinogen, is generated during the sterilization phase employed during the processing of Californian-style green ripe olives. It is possible to reduce the content of this toxic compound by applying different strategies during the processing of green ripe olives. The influence of different processing conditions on acrylamide content was studied in three olives varieties ("Manzanilla de Sevilla", "Hojiblanca", and "Manzanilla Cacereña"). Olives harvested during the yellow-green stage presented higher acrylamide concentrations than green olives. A significant reduction in acrylamide content was observed when olives were washed with water at 25 °C for 45 min (25% reduction) and for 2 h (45% reduction) prior to lye treatment. Stone olives had 21-26% higher acrylamide levels than pitted olives and 42-50% higher levels than sliced olives in the three studied varieties. When calcium chloride (CaCl2) was added to the brine and brine sodium chloride (NaCl) increased from 2% to 4%, olives presented higher concentrations of this contaminant. The addition of additives did not affect acrylamide levels when olives were canned without brine. Results from this study are very useful for the table olive industry to identify critical points in the production of Californian-style green ripe olives, thus, helping to control acrylamide formation in this foodstuff.

Comparative quantification of chlorophyll and polyphenol levels in grapevine leaves sampled from different geographical locations.

Near infrared spectroscopy (NIRS) and mid-infrared spectroscopy (MIRS) in combination with chemometric analysis were applied to discriminate the geographical origin of grapevine leaves belonging to the variety "Touriga Nacional" during different vegetative stages. Leaves were collected from plants of two different wine regions in Portugal (Dão and Douro) over the grapes maturation period. A sampling plan was designed in order to obtain the most variability within the vineyards taking into account variables such as: solar exposition, land inclination, altitude and soil properties, essentially. Principal component analysis (PCA) was used to extract relevant information from the spectral data and presented visible cluster trends. Results, both with NIRS and MIRS, demonstrate that it is possible to discriminate between the two geographical origins with an outstanding accuracy. Spectral patterns of grapevine leaves show significant differences during grape maturation period, with a special emphasis between the months of June and September. Additionally, the quantification of total chlorophyll and total polyphenol content from leaves spectra was attempted by both techniques. For this purpose, partial least squares (PLS) regression was employed. PLS models based on NIRS and MIRS, both demonstrate a statistically significant correlation for the total chlorophyll (R2P = 0.92 and R2P = 0.76, respectively). However, the PLS model for the total polyphenols, may only be considered as a screening method, because significant prediction errors, independently of resourcing on NIRS, MIRS or both techniques simultaneously, were obtained.

Phenylalanine Photoinduced Fluorescence and Characterization of the Photoproducts by LC-MS.

Phenylalanine (Phe) is a direct precursor of tyrosine and several neurotransmitters. The accumulation of Phe in the brain generates serious and not recoverable pathologies in children. Early detection in newborns is fundamental to apply the appropriate therapy and avoid irreversible health problems. Although fluorescence is a sensitive and selective technique for the determination of amino acids, the fluorescent analysis of Phe is limited since it exhibits a very low fluorescence quantum yield; however, the fluorescence of Phe increases drastically under UV irradiation when a peroxide medium is used. The aim of this research was to analyze the effect of the UV-radiation on Phe aqueous-peroxide solutions and to study the influence of the chemical environment on the photoinducted fluorescence process. The nature and characteristics of the fluorescent photoproducts generated under off-line UV irradiation in hydrogen peroxide medium were achieved by high performance liquid chromatography (HPLC) using a spectrophotometer detector (DAD) coupled in series with a mass spectrometer (MS) or with a fast scan spectrofluorimetric detector (FSFD). Environmental characteristics such as pH, initial concentration of Phe, hydrogen peroxide amount and irradiation time were studied in order to establish their influence on the formation of each one of the photoproducts. As the formation of several highly fluorescent photoproducts has been confirmed, the possibility of designing a chromatographic system with a post-column on-line photoreactor is open. The measure of the total fluorescence signal generated from Phe at the optimized irradiation time, could be used for the determination, with high sensitivity, of the initial amount of Phe in aqueous media, such as human serum or environmental samples. These aspects are being studied at present. .

Phenanthrene metabolites determination in human breast and cow milk by combining elution time-emission fluorescence data with multiway calibration.

Phenanthrene is the most released polycyclic aromatic hydrocarbon into the environment by anthropogenic action. Because of the absorption and biotransformation pathways, this compound is metabolized and the most abundant metabolites are hydroxylated derivatives, such as 1-, 2-, 3-, 4- and 9-hydroxyphenanthrene, which are excreted through biological fluids, included mammals milk. For the resolution and quantitation of co-eluted analytes, elution time-emission fluorescence matrices were analysed with different second-order calibration algorithms: n-way and unfolded partial least squares, both coupled with residual bilinearization (N-PLS/RBL and U-PLS/RBL), and multivariate curve resolution-alternative least squares (MCR-ALS). Once optimized the chromatographic parameters, in isocratic mode, the elution time was of 5.5 min. The second-order data were obtained exciting at 250 nm, with an emission range from 330 to 430 nm, each 1 nm, and elution time from 0 to 5.5 min each 5.4 s. The ranges for the second-order multivariate methods in validation samples were from 1.0 to 9.0 ng mL-1 for 1-, 2-, 3- and 4-hydroxyphenanthrene, and from 5.0 to 45.0 ng mL-1 for 9-hydroxyphenanthrene. Root mean square errors of prediction between 0.45 and 1.82 ng mL-1 (relative errors of prediction 7-22%) were obtained. The optimized procedures were applied in the analysis of human breast milk and in whole and semi-skimmed commercial cow milk. N-PLS/RBL and U-PLS/RBL algorithms show satisfactory results for the five metabolites with recoveries ranging between 82% and 115%.

Development of a method for the determination of advanced glycation end products precursors by liquid chromatography and its application in human urine samples.

A liquid chromatographic method with fluorimetric detection has been developed to determine the most abundant α-dicarbonyl compounds, generated as intermediates in the Maillard's reaction, previous derivatization to high fluorescent pteridinic derivatives. Hence, the biomarkers D-glucosone, 3-deoxyglucosone, glyoxal, methylglyoxal, diacetyl, 2,3-pentanedione, and phenylglyoxal were quantified using a gradient elution mode. The experimental conditions of the derivatization reaction and mobile phase composition were optimized. Linearity ranges (peak area versus α-dicarbonyl compound concentration) from 1.0 to 100.0 ng mL(-1) were obtained. Detection limits were comprised between 0.3 and 11.0 ng mL(-1). The high sensitivity of the method allows the determination of α-dicarbonyl compounds present in human urine, such as D-glucosone, 3-deoxyglucosone, glyoxal, and methylglyoxal, that are used as biomarkers, in order to investigate their roles in several diseases, with special emphasis in diabetes mellitus. With the aim of avoiding the interferences due to pteridinic compounds present in urine, a cleanup step with an ISOLUTE ENV+ cartridge was carried out. The concentrations of these urinary biomarkers have been reported as a normalized ratio to urinary creatinine, and determined in healthy and in diabetic volunteers, of different ages and sex. In all urine samples, standard addition and external calibration procedures were applied and compared.