Pyrazine composition of wood smoke as influenced by wood source and smoke generation variables

Development of a Solid-Phase Microextraction-Gas Chromatography/Mass Spectrometry Method for Quantifying Nitrogen-Heterocyclic Volatile Aroma Compounds: Application to Spirit and Wood Matrices

Over wood aging, matured spirits developed a complex aromatic bouquet where roasted-like notes were often perceived. Since many nitrogen heterocycles were related to these olfactory nuances, a headspace solid-phase microextraction (HS-SPME) coupled to gas chromatography-mass spectrometry was developed and validated to quantify them in both spirit and wood matrices. The various parameters affecting the extraction of the analytes from both spirit and wood samples were first investigated (i.e., fiber coating phase, dilution, pH and volume sample, adding salt, extraction time and temperature, and incubation time) to determine the best compromise for a single-run analysis of the whole set of studied compounds. Good linearity (R² > 0.99), repeatability, reproducibility, accuracy and low detection, and quantification limits were obtained, making this analytical method a suitable tool for routine analysis of the selected nitrogen compounds. Fifteen pyrazines, three pyrroles, and three quinolines were quantified in a series of oak wood and commercial spirit samples where some of them were identified for the first time. The significant impact of some barrel features and the spirit in-wood maturation step on the N-heterocycle profile in both matrices were finally discussed.

Fingerprints of acacia aging treatments by barrels or chips based on volatile profile, sensorial properties, and multivariate analysis

BACKGROUND

Despite the acceptance of the use of chips as an alternative enological practice to traditional barrels, there is substantial interest in looking for parameters that enable the aging technique to be identified. In the present study, the volatile compound composition and sensorial characteristics of wines aged with chips and barrels of acacia wood were monitored with the aim of finding fingerprints that could be used to discriminate between the two types of aging.

RESULTS

Principal component analysis (PCA) calculated from chemical outputs permitted the two aging techniques to be distinguished. After 4 months of aging in barrels, concentrations of vanillin, ferulic acid, syringaldehyde, and furfural decreased considerably due to the higher oxidation produced by the acacia wood's porosity. This fact made it more difficult to discriminate between those wines aged in barrels for the longest times. On the other hand, PCA applied to sensorial data allowed a clear differentiation between wines aged in acacia barrels for longer periods and those macerated with chips, due to the notable presence of sensory attributes described as acacia wood, nutty, honeyed, and toasty.

CONCLUSION

Chemical and sensorial data can be regarded as complementary methods to obtain fingerprints that enable differentiation between the two different aging techniques by means of acacia wood. © 2018 Society of Chemical Industry.

Experimental design-based isotope-dilution SPME-GC/MS method development for the analysis of smoke flavouring products

For the implementation of Regulation (EC) No 2065/2003 related to smoke flavourings used or intended for use in or on foods a method based on solid-phase micro extraction (SPME) GC/MS was developed for the characterisation of liquid smoke products. A statistically based experimental design (DoE) was used for method optimisation. The best general conditions to quantitatively analyse the liquid smoke compounds were obtained with a polydimethylsiloxane/divinylbenzene (PDMS/DVB) fibre, 60°C extraction temperature, 30 min extraction time, 250°C desorption temperature, 180 s desorption time, 15 s agitation time, and 250 rpm agitation speed. Under the optimised conditions, 119 wood pyrolysis products including furan/pyran derivatives, phenols, guaiacol, syringol, benzenediol, and their derivatives, cyclic ketones, and several other heterocyclic compounds were identified. The proposed method was repeatable (RSD% <5) and the calibration functions were linear for all compounds under study. Nine isotopically labelled internal standards were used for improving quantification of analytes by compensating matrix effects that might affect headspace equilibrium and extractability of compounds. The optimised isotope dilution SPME-GC/MS based analytical method proved to be fit for purpose, allowing the rapid identification and quantification of volatile compounds in liquid smoke flavourings.

Chemical characterization of commercial liquid smoke products

The objective of this study was to determine important chemical characteristics of a full-strength liquid smoke, Code 10-Poly, and three refined liquid smoke products (AM-3, AM-10 and 1291) commercially available (Kerry Ingredients and Flavors, Monterey, TN). The pH of the products were significantly different (P < 0.05) and ranged from 2.3 (Code 10-Poly) to 5.7 (1291). The pH was inversely correlated with titratable acidity (R (2) = 0.87), which was significantly different (P < 0.05) among products ranging from 10.3% acetic acid (Code 10-Poly) to 0.7% acetic acid (1291). Total phenol content was quantified using the Gibbs reaction; the only liquid smoke containing appreciable level of phenolic compounds was Code 10-Poly at 3.22 mg mL(-1). Gas chromatography-mass spectrometry (GC-MS) analysis of liquid smoke dichloromethane extracts revealed that carbonyl-containing compounds were major constituents of all products, in which 1-hydroxy-2-butanone, 2(5H)-furanone, propanal and cyclopentenone predominated. Organic acids were detected by GC-MS in all extracts and correlated positively (R (2) = 0.98) with titratable acidity. The GC-MS data showed that phenolic compounds constituted a major portion of Code 10-Poly, and were detected only in trace quantities in 1291. The refined liquid smokes had lighter color, lower acidity, and reduced level of carbonyl-containing compounds and organic acids. Our study revealed major differences in pH, titratable acidity, total phenol content, color and chemical make-up of the full-strength and refined liquid smokes. The three refined liquid smoke products studied have less flavor and color active compounds, when compared with the full-strength product. Furthermore, the three refined products studied have unique chemical characteristics and will impart specific sensorial properties to food systems. Understanding the chemical composition of liquid smokes, be these refined or full-strength products, is an important step to establish their functions and appropriate use in food systems.

Smoke-derived taint in wine: effect of postharvest smoke exposure of grapes on the chemical composition and sensory characteristics of wine

Although smoke exposure has been associated with the development of smoke taint in grapes and subsequently in wine, to date there have been no studies that have demonstrated a direct link. In this study, postharvest smoke exposure of grapes was utilized to demonstrate that smoke significantly influences the chemical composition and sensory characteristics of wine and causes an apparent 'smoke taint'. Verdelho grapes were exposed to straw-derived smoke for 1 h and then fermented according to two different winemaking treatments. Control wines were made by fermenting unsmoked grapes. Sensory studies established a perceivable difference between smoked and unsmoked wines; smoked wines were described as exhibiting 'smoky', 'dirty', 'earthy', 'burnt' and 'smoked meat' characteristics. Quantitative analysis, by means of gas chromatography-mass spectrometry, identified guaiacol, 4-methylguaiacol, 4-ethylguaiacol, 4-ethylphenol, eugenol, and furfural in each of the wines made from smoked grapes. However, these compounds were not detected in the unsmoked wines, and their origin is therefore attributed to the application of smoke. Increased ethanol concentrations and browning were also observed in wines made from grapes exposed to smoke.