Chemometrical development and comprehensive validation of a solid phase microextraction/gas chromatography-mass spectrometry methodology for the determination of important free and bound primary aromatics in Greek wines

In this work, a solid-phase microextraction/gas chromatography-mass spectrometry (SPME/GC-MS) methodology was developed for the determination of 21 free and glycosidically-bound volatile varietal aroma compounds in wines. Initially, a comparison was made of 5 commercially available SPME fibers for the isolation/preconcentration of the target compounds in the headspace (HS) and direct immersion (DI) modes. The statistical significance of the microextraction variables was evaluated using a 2-level Plackett-Burman experimental design; the most significant variables were further optimized using a modified Simplex procedure. Using the selected conditions, a GC-MS method was fully validated for the quantitative determination of the 21 free primary aroma compounds. The hydrophilic bound precursors were isolated by solid-phase extraction (SPE), enzymatically hydrolyzed to liberate them as the free compounds and further detected by SPME/GC-MS. The method has been successfully applied to the analysis of 20 Greek white wine samples. © 2013 Elsevier B.V

Comparison of solid-phase extraction sorbents for the fractionation and determination of important free and glycosidically-bound varietal aroma compounds in wines by gas chromatography-mass spectrometry

A critical comparison was made of seven solid-phase extraction (SPE) sorbents for the fractionation and isolation of 21 important free and glycosidically-bound varietal volatile aroma compounds. The sample was subjected to SPE and the free aromatics were eluted with dichloromethane followed by elution of the glucoconjugates with methanol; after fractionation, the free fraction was analyzed directly by GC-MS while the sugar-bound fraction was enzymatically hydrolyzed to liberate the free compounds before analysis by GC-MS. The extraction efficiency for the free compounds was evaluated based on the analytes' signal recovery and for the glycosidically-bound compounds in terms of the relative peak areas. The best results for both the free and bound fractions were obtained with the Isolute ENV+ resin. Following selection of the most efficient SPE material, a GC-MS method was validated (in terms of selectivity, linearity, limits of detection (LODs) and limits of quantification (LOQs), recovery, repeatability, within-laboratory reproducibility and uncertainty) for the quantitative determination of the free primary volatiles in white wines. Validation results are presented at 4 fortification levels (10, 50, 200 and 500 μL-1). Regarding linearity, the correlation coefficient of the matrix-matched calibration plots was ≥0.99 for all the compounds. The LOQs were in the range 0.6-17.5 μg L-1. Recoveries ranged from 61% to 120% while the% relative standard deviation of the within-laboratory reproducibility was in the range 1.3% to 17.7%. Finally, the% expanded uncertainty ranged from 3.1% to 40.3%. The method has been successfully applied to the analysis of 20 white wine samples. © 2013 Versita Warsaw and Springer-Verlag Wien

Development and application of methodologies for the determination of primary aroma compounds in white wines with gas chromatography-mass spectrometry

In this thesis, a SPE/GC–MS methodology and a SPME/GC–MS methodology were developed for the determination of 21 free and glycosidically-bound volatile varietal aroma compounds (terpenes, C6 alcohols, C13 norisoprenoids and benzene derivatives) in wines.Initially, a critical comparison was made of seven SPE sorbents for the fractionation and isolation of the 21 free and bound target compounds. The most satisfactory extraction efficiency for both free and bound fractions was obtained with the Isolute ENV+ resin.For the isolation/preconcentration of the target compounds with the SPME-GC/MS method, a comparison was made of five commercially available SPME fibers in the headspace (HS) and direct immersion (DI) modes. The fibre coated with PDMS/DVB in the direct immersion mode was selected, as it yielded satisfactory extraction efficiency and the best reproducibility. The statistical significance of seven microextraction variables was evaluated using a 2-level Plackett–Burman experimental design. Then the five statistically most significant factors were optimised using a modified Simplex procedure.The two methods were fully validated (in terms of selectivity, linearity, limits of detection and quantification, recovery, repeatability, reproducibility and uncertainty for the quantitative determination of the 21 free aroma compounds and were successfully applied to the analysis of 20 monovarietal white wine samples from indigenous and international varieties of Vitis vinifera L. cultivated in Greece.Σε αυτήν τη διατριβή, πραγματοποιήθηκε ανάπτυξη μίας μεθοδολογίας SPE-GC/MS και χημειομετρική ανάπτυξη μίας μεθοδολογίας SPME-GC/MS για τον προσδιορισμό 21 ελεύθερων και γλυκοζιτικά δεσμευμένων πρωτογενών αρωματικών συστατικών (τερπενικών ενώσεων, C6 αλκοολών, C13 νορισοπρενοειδών και βενζολικών παραγώγων) σε λευκούς ξηρούς οίνους.Αρχικά, πραγματοποιήθηκε συγκριτική μελέτη μεταξύ επτά εμπορικά διαθέσιμων SPE μικροστηλών για το διαχωρισμό και την απομόνωση των ελεύθερων και των πρόδρομων αρωματικών ενώσεων με SPE. Την καλύτερη επίδοση, με κριτήριo την ανάκτηση σήματος των ελεύθερων και μετά από ενζυμική υδρόλυση το αναλυτικό σήμα των δεσμευμένων συστατικών, είχε η μικροστήλη Isolute ENV+.Για την ανάπτυξη της μεθοδολογίας SPΜE-GC/MS, αρχικά πραγματοποιήθηκε συγκριτική μελέτη μεταξύ πέντε εμπορικά διαθέσιμων ινών SPΜE, με δειγματοληψία από την υγρή και την αέρια φάση του δείγματος. Επιλέχθηκε μικροεκχύλιση από την υγρή φάση με ίνα PDMS/DVB καθώς με αυτό το συνδυασμό παρατηρήθηκε ικανοποιητική ανάκτηση και η βέλτιστη αναπαραγωγιμότητα. Με εφαρμογή μερικού πειραματικού σχεδιασμού (Plackett-Burman), εξετάσθηκε η επίδραση στη μικροεκχύλιση επτά παραγόντων και επιλέχθηκαν εκείνοι με τη μεγαλύτερη στατιστική σημαντικότητα. Στη συνέχεια, για τη βελτιστοποίηση των πέντε σημαντικότερων παραγόντων εφαρμόσθηκε τροποποιημένη μέθοδος Simplex.Οι δύο μέθοδοι επικυρώθηκαν για τον ποσοτικό προσδιορισμό των 21 ελεύθερων αρωματικών συστατικών με αξιολόγηση ως προς την ειδικότητα, τη γραμμικότητα, τα όρια ανίχνευσης και ποσοτικοποίησης, την ανάκτηση, την αναπαραγωγιμότητα, την επαναληψιμότητα και την αβεβαιότητά. Στη συνέχεια, εφαρμόσθηκαν επιτυχώς, για την ανάλυση 20 λευκών μονοποικιλιακών οίνων από ελληνικές και διεθνείς ποικιλίες αμπέλου Vitis vinifera

Influence of cluster thinning on the amino acids concentration of musts and wines of the variety Vilana. Effect on wine volatile compounds

In this work, the influence of cluster thinning on the amino acids concentration of musts and wines was studied. Three vineyards were selected from Peza district of Crete where the white vine variety Vilana is cultivated. One part of each vineyard, containing 100 vines was divided in two sections. The first was used as reference while in the second section, cluster thinning to 50%, just before veraison, was applied. The experimentation was repeated for two continuous years. In 1996, the reference sections yielded 35.5 – 46.7 t/h while the other sections, where cluster thinning took place, yielded 16.5 – 23.0 t/h. The next year, the yields were 43.2 – 48.4 t/h and 12.6 – 14.0 t/h respectively. In all musts and wines, 18 amino acids were determined with the use of HPLC and proline was determined colorimetrically. The volatile components of the wines were also measured because, as it is known, the amino acids contribute to the formation of some higher alcohols, ethyl esters and acetates. From this work the following conclusions were made: The musts and the wines from Vilana variety are poor in amino acids and their levels vary from one year to another. This variation is related to the climatic conditions of the period of maturation but the profile of these acids seems invariable. The musts of Vilana variety deriving from vineyards with cluster thinning, which lead to low yield, contain higher levels of amino acids. This is important, given that a must rich in amino acids, positively influences not only the fermentation process evolution but also the enrichment of the wines in volatile components. Particularly for the Vilana variety, which is poor in amino acids and without any typical aroma, the high yields have a negative effect on their wine quality

Ochratoxin a occurrence in Greek dry and sweet wines

Aims: To assess ochratoxin A (OTA) presence in Greek wines, according to the production area and the technology, as OTA risk is higher in wines from southern Europe. The effect of fining agents was examined in order to investigate OTA reduction. Methods and results: Dry and sweet wines issued from research programs and trade wines were analyzed, according to the official HPLC method. Greek dry wines do not exceed the European limit of 2 ng/mL. The amount of OTA (in ng/mL) varies between 0 - 1,18 for dry white wines, 0 -1,00 for dry red wines. Among sweet wines, only fortified wines without alcoholic fermentation range between 0,50 -7,64, while other sweet wines range between 0,05 -1,73. Dry yeast reduced OTA by 25 - 60 % according to dosage and duration (1-10 weeks) while the effect of bentonite was 33 - 40 % reduction for a treatment of 3-6 days. Conclusion: The picture for Greek wine production is positive, even in case of a future lowering of the European limit. OTA risk seems higher in the islands, particularly for some dessert wines. Results from wine treatment with fining agents support the theory of OTA adsorption onto suspended solids and the beneficial effect of yeast presence. Significance and impact of study: Assessment of OTA danger for Greek wines and information concerning the effect of fining agents contribute to the production of wines free from contaminants and support wine economy

Effect of Fortification with Mushroom Polysaccharide β-Glucan on the Quality of Ovine Soft Spreadable Cheese

In the present work, a fresh spreadable cheese from ovine milk with or without (control) fortification with β-glucan was manufactured. β-Glucan was extracted from the mushroom Pleurotus ostreatus and its concentration in the cheese was 0.4% (w/w). The composition, biochemical, and sensory properties of the cheeses during 21 days of storage were determined. At the end of storage, cheese fortified with beta-glucan had 75.26% moisture content, 10.30% fat, 1.71% salt, and 8.50% protein. Generally, the addition of β-glucan at this concentration did not significantly affect the composition, color, and viscosity measurements or the level of proteolysis and lipolysis and the antioxidant activity of the cheeses. However, cheese fortified with β-glucan showed a higher moisture content than control cheese on the 1st and 21st day of storage while the levels of proteolysis and the sensory properties of the cheeses were unaffected. During the sensory evaluation, panelists evaluated cheese with β-glucan with higher scores regarding the flavor characteristic compared to control cheese. The major free fatty acid was acetic acid in both cheeses and its concentration was higher in cheese with β-glucan. The results of the present study could be used by the dairy industry for manufacturing new products with improved health benefits

Impact on cytoprotective efficacy of intermediate interval between amifostine administration and radiotherapy: A retrospective analysis

Purpose: To evaluate the cytoprotective impact of the interval between amifostine administration and radiotherapy (RT). Methods and Materials: In a nonrandomized study, we reviewed the records of 177 patients with tumors localized in the pelvis (prostate, bladder, or gynecologic cancer), upper abdomen (pancreas, stomach, kidney), thorax (lung and breast cancer), head and neck (nasopharynx), soft tissue (sarcomas), and central nervous system. The patient records were stratified according to whether the patients had undergone RT either 25-40 min (Group 1, 96 subjects) or 10-15 min (Group 2, 81 subjects) after i.v. amifostine administration. The mean toxicity score was the mean value of recorded acute radiation toxicity. The mean interruption time was the mean value of the recorded interruption time due to radiation toxicity. Results: A significantly reduced severity of symptoms related to oral (p = 0.023), esophageal (p = 0.05) and rectal (p = 0.015) mucosa was noted in Group 2. A statistically significant reduction in the mean toxicity score (p <0.001) and mean interruption time (p = 0.001) was observed in Group 2 vs. Group 1. In terms of the incidence of radiation-induced dermatitis and alopecia, multivariate logistic analysis revealed only the total dose (P 0.018) and the amifostine-RT interval (p = 0.002) as independent factors. Conclusion: A significantly better cytoprotective effect of amifostine against radiation-induced mucositis, dermatitis, and alopecia was noted if RT was administered no later than 15 min after i.v. amifostine infusion. The results presented here need additional investigation with randomized prospective trials. (C) 2004 Elsevier Inc