Sorption behavior of volatile phenols at the oak wood/wine interface in a model system

Scalping of aroma compounds from food simulants into polyethylene terephthalate laminated steel

BACKGROUND

Aroma scalping is a very common problem and can affect the sensory quality of packaged food. To study the aroma scalping characteristics of polyethylene terephthalate laminated steel (PET-LS), the sorption kinetics of six common aroma compounds (2-pentanone, 2-heptanone, hexanal, citral, butyl acetate, isopentyl acetate) in foods were assessed for drawn-redrawn cans made with PET-LS.

RESULTS

Storage temperature and initial concentration were proved as important factors to affect compound sorption and diffusion for flavors. The correlation between logarithm of equilibrium absorption ln M_∞ and reciprocal of absolute temperature 1/T showed good linear relationship (R²  = 0.9380-0.9998) at 4 °C, 20 °C and 50 °C, and the M_∞ obtained by the experiment was very close to the predicted value at 37 °C. At low initial concentration (below 500 µL L^-1 ), the absorption capacity and initial concentration showed a slow linear growth trend, whereas there was a rapid change at high initial concentration. The values of diffusion coefficient D were on the order of 10^-11 -10^-12  m²  day^-1 , which were lower than reported for other polymer materials (linear low-density polyethylene, polybutylene succinate, polylactic acid).

CONCLUSION

The equilibrium absorption amount of each flavor component was dependent on the temperature under the same concentration (500 µL L^-1 ). The Fickian diffusion model was used for fitting the experimental kinetics values satisfactorily (R²  = 0.9158-0.9885). © 2019 Society of Chemical Industry.

Volatile composition and sensory characteristics of Carménère wines macerating with Colombian (Quercus humboldtii) oak chips compared to wines macerated with American (Q. alba) and European (Q. petraea) oak chips

Different oak species or origins have been studied to find an alternative to traditional ones and Quercus humboldtii from Colombia is a candidate. Some studies analyse the composition of this oak, but no work has been found to study its use for wine treatment. The aim was to evaluate volatile composition of toasted Q. humboldtii oak chips and the wines treated with these chips. To evaluate its oenological potential Q. alba and Q. petraea have been included in this trial. The wines were subjected to a sensory analysis. Results indicated that oak chips and wines macerated for 90 days with toasted Colombian chips exhibited higher 5-methylfurfural, guaiacol, trans-isoeugenol and syringol concentrations than others, while the furfural and cis-β-methyl-γ-octalactone content was lower. Sensory analysis showed that the wines treated with Colombian oak presented more notes of smoked and less of coconut. Therefore, this oak could probably be considered suitable for ageing.

Waterpipe smoke: source of toxic and carcinogenic VOCs, phenols and heavy metals?

The use of the waterpipe, a traditional aid for the consumption of tobacco, has spread worldwide and is steadily increasing especially among the youth. On the other hand, there is a lack of knowledge regarding the composition of mainstream waterpipe smoke and the toxicological risks associated with this kind of smoking habit. Using a standardized machine smoking protocol, mainstream waterpipe smoke was generated and further analyzed for twelve volatile organic compounds (VOCs) and eight phenolic compounds by applying gas chromatography-mass spectrometry and reverse-phase high-performance liquid chromatography-fluorescence detection, respectively. Additionally, seventeen elements were analyzed in waterpipe tobacco and charcoal prior to and after smoking, applying inductively coupled plasma-mass spectrometry to assess the maximum exposure of these elements. For the first time ever, we have been able to show that waterpipe mainstream smoke contains high levels of the human carcinogen benzene. Compared with cigarette smoke yields, the levels were 6.2-fold higher, thus representing a significant health hazard for the waterpipe smoker. Furthermore, we found that waterpipe mainstream smoke contains considerable amounts of catechol, hydroquinone and phenol, each of which causing some health concern at least. The analysis of waterpipe tobacco and charcoal revealed that both matrices contained considerable amounts of the toxic elements nickel, cadmium, lead and chromium. Altogether, the data on VOCs, phenols and elements presented in this study clearly point to the health hazards associated with the consumption of tobacco using waterpipes.

Effect of ethanol on the sorption of four targeted wine volatile compounds in a polyethylene film

The objectives of this study were to demonstrate that the presence of ethanol in a solution containing two esters and two aromatic alcohols has several consequences on the sorption of these compounds into polyethylene (PE) film. First, sorption of ethanol into the PE film occurred at the same time as water and reached 8 kg m(-3) using 12% v/v of ethanol. This sorption was associated with an increase in PE crystallinity, which may have prevented the sorption of volatile compounds despite their strong affinity with PE film, as evaluated by Hansen solubility parameters. Moreover, increasing the ethanol concentration increased the solubility of the four volatile compounds. In the case of aromatic alcohols, the sorption was decreased in the presence of ethanol as expected. In the case of esters, as their hydrolysis was substantial in the presence of water, the consequence was a higher sorption into the PE film in the presence of ethanol than in its absence. Nevertheless, the sorption also depended on the concentration of ethanol and the heterogeneity of the ethanol-water mixture as well as the presence of other volatile compounds, as in the case of 4-ethylphenol. In conditions simulating wine packaging, losses of volatile compound by sorption and by permeation estimated after only 5 days of contact varied between 0.08 and 25% for 2-phenylethanol and ethyl hexanoate, respectively.

In-depth search focused on furans, lactones, volatile phenols, and acetals as potential age markers of Madeira wines by comprehensive two-dimensional gas chromatography with time-of-flight mass spectrometry combined with solid phase microextraction

The establishment of potential age markers of Madeira wine is of paramount significance as it may contribute to detect frauds and to ensure the authenticity of wine. Considering the chemical groups of furans, lactones, volatile phenols, and acetals, 103 volatile compounds were tentatively identified; among these, 71 have been reported for the first time in Madeira wines. The chemical groups that could be used as potential age markers were predominantly acetals, namely, diethoxymethane, 1,1-diethoxyethane, 1,1-diethoxy-2-methyl-propane, 1-(1-ethoxyethoxy)-pentane, trans-dioxane and 2-propyl-1,3-dioxolane, and from the other chemical groups, 5-methylfurfural and cis-oak-lactone, independently of the variety and the type of wine. GC × GC-ToFMS system offers a more useful approach to identify these compounds compared to previous studies using GC-qMS, due to the orthogonal systems, that reduce coelution, increase peak capacity and mass selectivity, contributing to the establishment of new potential Madeira wine age markers. Remarkable results were also obtained in terms of compound identification based on the organized structure of the peaks of structurally related compounds in the GC × GC peak apex plots. This information represents a valuable approach for future studies, as the ordered-structure principle can considerably help the establishment of the composition of samples. This new approach provides data that can be extended to determine age markers of other types of wines.

Interaction Mechanisms between guaiacols and lignin: the conjugated double bond makes the difference

Lignin is considered to be responsible for a selective sorption of phenolic compounds on wood. In order to investigate the mechanisms involved, two similar guaiacol compounds--only differing by the nature of the para side chain--were adsorbed on oak wood extracted lignin. Vapor sorption-desorption isotherms indicated that about 3.5 wt % of 4-vinylguaiacol is adsorbed near saturation whereas it is only 0.8% for 4-ethylguaiacol. For both compounds, the isotherms displayed a hysteresis though significantly greater for 4-vinylguaiacol. Analyses of the hydroxyl stretching region of FTIR spectra of the lignin/4-ethylguaiacol and lignin/4-vinylguaiacol complexes indicated that physisorption via hydrogen bonds occurs for both sorbates with lignin phenolic hydroxyl groups but which would be more condensed for the former than for the latter. According to NMR spectra, these phenolic hydroxyl groups correspond to non-etherified guaiacyl subunits. In contrast with other para substituents, the conjugated vinyl bond favors not only physisorption but also chemisorption as witnessed by the fact that upon desorption in the vapor phase, even after pumping under dynamic vacuum for several days, about 1 wt % of 4-vinylguaiacol remains adsorbed onto lignin.

Volatile compounds of red wines macerated with Spanish, American, and French oak chips

The volatile composition of a red wine aged for 2 months with three different Spanish oak chips (Quercus pyrenaica and Quercus petraea) from different regions of Castilla y León was compared with that of wines aged with American and French chips. In general, the extraction kinetics showed that the maximum concentration of the volatile compounds extracted from wood can be reached in only 1 month. In the final wines, the levels of furanic aldehydes and eugenol were higher in the wines macerated with Spanish chips, whereas cis-whiskey-lactone, vanillin, and methyl vanillate showed higher levels in wines treated with American chips. Among the wines treated with the different Spanish chips, the differences observed in the volatile composition were more related to the geographical origin of the forest than to the botanical species. In general, the wines macerated with Spanish chips showed levels of oak-related volatile compounds that were more similar to those macerated with French chips than to those macerated with American chips.

Role of wood macromolecules on selective sorption of phenolic compounds by wood

Wood is a complex structure of various macromolecules, mainly cellulose, hemicellulose, and lignin. Although the sorption process of some organic compounds by wood has been elucidated, the relative contribution of its different fractions in the sorption mechanism is not clearly determined. Certain works predict the amount of organic compounds sorbed on wood as a direct relationship to its lignin fraction. All wood macromolecules, however, seem to have the capacity to sorb organic compounds. Sorption of phenolic compounds on individual wood macromolecules has been studied and compared to that on wood. Wood-water partition coefficients ( K wood) for phenolic volatiles and their sorption rates in the presence of lignin display a linear relationship. Results show that cellulose and hemicellulose sorb all phenolic compounds without apparent distinction, whereas lignin is a selective sorbent of these compounds. Sorbant availability and sorbate chemical structure seem to be the key factors governing the sorption mechanism. Sorption kinetics study gives apparent diffusion coefficient values of aroma compounds, bringing new kinetic data for understanding the ternary system of wood, hydroalcoholic solution, and phenolic compounds.