P.J. Martín-Álvarez

Polydimethylsiloxane solid-phase microextraction-gas chromatography method for the analysis of volatile compounds in wines. Its application to the characterization of varietal wines.

A study was made of the validity of the solid-phase microextraction method, using a polydimethylsiloxane coated fused-silica fiber, for the extraction-desorption of the minor volatile compounds from wine before their gas chromatographic analysis. The aspects considered were the influence of ethanol on extraction, repeatability, limits of detection, linearity and recovery of compounds. This method, together with the direct injection of the major volatile compounds, was applied to 16 varietal wines. The findings indicate that the method is a highly suitable technique for the analysis of wines and that the volatile composition of wines depends, at least partly, on the grapes with which they have been made.

Changes in gas-chromatographic volatiles of young Airen wines during bottle storage

Abstract Twenty-six commercial Airen variety wines from La Mancha (Spain) corresponding to four successsive vintages (1990–1993) were analysed by gas chromatography (GC) and characterized through 30 minor and major volatiles. Stepwise discriminant analysis applied to the GC variables obtained showed that, as in other varietal wines, diethyl succinate content increased during 3 years of storage, whereas isopentyl acetate and 2-phenylethyl acetate decreased over this period. A progressive increase in acetaldehyde content was also detected.

Antibacterial activity of wine phenolic compounds and oenological extracts against potential respiratory pathogens

Aims:  To investigate the effect of seven wine phenolic compounds and six oenological phenolic extracts on the growth of pathogenic bacteria associated with respiratory diseases (Pseudomonas aeruginosa, Staphylococcus aureus, Moraxella catarrhalis, Enterococcus faecalis, Streptococcus sp Group F, Streptococcus agalactiae and Streptococcus pneumoniae).

Analytical performance of three commonly used extraction methods for the gas chromatography-mass spectrometry analysis of wine volatile compounds.

The analytical performance of three extraction procedures based on cold liquid-liquid extraction using dicloromethane (LLE), solid phase extraction (SPE) using a styrene-divinylbenzene copolymer and headspace solid phase microextraction (SPME) using a carboxen-polydimethylsiloxane coated fibre has been evaluated based on the analysis of 30 representative wine volatile compounds. From the comparison of the three procedures, LLE and SPE showed very good linearity covering a wide range of concentrations of wine volatile compounds, low detection limits, high recovery for most of the volatile compounds under study and higher sensitivity compared to the headspace-SPME procedure. The latter showed in general, poor recovery for polar volatile compounds. Despite some drawbacks associated with the LLE and SPE procedures such as the more tedious sampling treatment and the use of organic solvents, the analytical performance of both procedures showed that they are more adequate for the analysis of wine volatiles.

Inactivation of oenological lactic acid bacteria (Lactobacillus hilgardii and Pediococcus pentosaceus) by wine phenolic compounds

Aims:  To investigate the inactivation properties of different classes of phenolic compounds present in wine against two wine isolates of Lactobacillus hilgardii and Pediococcus pentosaceus, and to explore their inactivation mechanism.

Application of partial least squares (PLS) regression to predict the ripening time of Manchego cheese

Partial least squares (PLS) regression was used to predict the ripening time of Manchego cheese, based on some physicochemical parameters and secondary proteolysis indices of 63 standard Manchego cheeses manufactured in different seasons (autumn, winter and spring). PLS regression demonstrated that the variables that most contributed to predict the ripening time of the cheeses were water activity (aw), pH and dry matter (DM). The prediction model obtained yielded good results for the prediction of the ripening times of commercial Manchego cheeses manufactured in the same factory as the standard cheeses, since the root mean square error of prediction was 11.9 days. The model was also good for the prediction of the ripening times of commercial Manchego cheeses manufactured in different factories.

Impact of the nonvolatile wine matrix composition on the in vivo aroma release from wines.

The impact of the nonvolatile wine matrix composition on the retronasal aroma release of four volatile compounds added to different types of wines has been evaluated. For this purpose, a tailor-made retronasal aroma trapping device (RATD) was used to entrap the exhaled breath of six panelists previously trained in a specific consumption procedure. Five wines of different composition (white wine, sparkling white wine, young red wine, aged red wine, and a sweet wine) were evaluated. Prior to the evaluation, with the exception of the sweet wine, the wines were adjusted to the same ethanol content and aromatized with a mixture of four target volatile compounds. Aroma release data were submitted to multivariate statistical analysis in order to relate wine chemical composition and aroma release during wine drinking. Results showed interindividual differences and a clustering of panelists among lower and higher aroma releasers, which was in agreement to the differences in their breathing capacity. A significant influence of the matrix composition in the low aroma releasers group during wine consumption was observed. The consumption of red wines provoked a significantly higher aroma release than the consumption of white and sweet wines. From the chemical composition determined in the wine samples (pH, total acidity, total polyphenols, neutral polysaccharides, residual sugar, and nitrogenous compounds), the amount of total polyphenols was better correlated with the observed effect.

Colour and moisture changes during the manufacture of iberian dry-cured ham caused by some biotic and abiotic factors

The effects of some biotic (pig-rearing system and muscle location) and abiotic factors (processing time and drying location) on colour (L*, a* and b*) and moisture changes during the manufacture of Iberian ham were studied. The levels of L* (from 27.14 to 44.44), a* (from 6.10 to 19.84) and b* (from 2.18 to 8.72) parameters, and moisture (from 31.71 to 75.04) decreased (p 0.05) as processing time increased. L*, a* and b* were strongly influenced by muscle location and their values were smaller (p 0.05) in semimembranosus than in biceps femoris, as occurred with moisture. The rearing system produced differences (p 0.05) in a* at the first stage and in L* and b* at the final stage of processing. Drying location, probably in association with natural climatic conditions, caused differences (p 0.05) at only the final stage of processing in a* and b* parameters. The variations in colour parameters were mainly affected by rearing system and muscle location.

Evaluation of a programmed temperature vaporizer for quantitative analysis by split injection

Abstract The influence of several parameters affecting sampling with cold temperature-programmed injection were studied. The parameters were types and lengths of packings used in the glass insert, end temperatures in the sampling device, solvents and splitting ratio. The accuracy and precision of the sampling was measured for a test mixture of n -alkanes using a programmed temperature vaporizer in the split mode.

Evolution of red wine anthocyanins during malolactic fermentation, postfermentative treatments and ageing with lees.

A comparative study was conducted on nine batches of wine, from the same initial wine, subjected to malolactic fermentation and ageing in barrels, under different technological conditions: Malolactic fermentation in barrel or in tank, with or without wine clarification, ageing with or without lees and stirring or no stirring of the lees. Samples were taken of the initial wine, of the wine at the end of malolactic fermentation, of the wines after clarifying treatments, and after 3, 6, 9, 12 and 14 months of ageing in the barrel, making a total of 48 wines. As a result of the anthocyanin analysis of all the wines studied, a total of 21 different anthocyanin compounds were detected, which can be classified into four groups: simple glucosides, acetyl glucosides, cinnamoyl glucosides and pyroanthocyanins. During MLF, it was shown that the effect of the container used seems to be more important than the metabolic activity of the bacteria responsible for the process. From application of the LSD test, significant differences were found in the concentrations of all the anthocyanin compounds identified due to ageing time and significant differences were also revealed for most anthocyanin compounds in relation to the manufacturing method, especially the presence or absence of lees.