Tobacco smoke chemistry. 2. Alkyl and alkenyl substituted guaiacols found in cigarette smoke condensate

Odor-Reduced HDPE-Lignin Blends by Use of Processing Additives

The comprehensive use of natural polymers, such as lignin, can accelerate the replacement of mineral oil-based commodities. Promoting the material recovery of the still underutilized technical lignin, polyolefin-lignin blends are a highly promising approach towards sustainable polymeric materials. However, a limiting factor for high-quality applications is the unpleasant odor of technical lignin and resulting blends. The latter, especially, are a target for potential odor reduction, since heat- and shear-force intense processing can intensify the smell. In the present study, the odor optimization of kraft and soda HDPE-lignin blends was implemented by the in-process application of two different processing additives–5% of activated carbon and 0.7% of a stripping agent. Both additives were added directly within the compounding process executed with a twin screw extruder. The odor properties of the produced blends were assessed systematically by a trained human panel performing sensory evaluations of the odor characteristics. Subsequently, causative odor-active molecules were elucidated by means of GC-O and 2D-GC-MS/O while OEDA gave insights into relative odor potencies of single odorants. Out of 70 different odorants detected in the entirety of the sample material, more than 30 sulfur-containing odorants were present in the kraft HDPE-lignin blend, most of them neo-formed due to high melt temperatures during extrusion, leading to strong burnt and sulfurous smells. The addition of activated carbon significantly decreased especially these sulfurous compounds, resulting in 48% of overall odor reduction of the kraft blend (mean intensity ratings of 5.2) in comparison to the untreated blend (10.0). The applied stripping agent, an aqueous solution of polymeric, surface-active substances adsorbed onto a PP carrier, was less powerful in reducing neo-formed sulfur odorants, but led to a decrease in odor of 26% in the case of the soda HDPE-lignin blend (7.4). The identification of single odorants on a molecular level further enabled the elucidation of odor reduction trends within single compound classes. The obtained odor reduction strategies not only promote the deodorization of HDPE-lignin blends, but might be additionally helpful for the odor optimization of other natural-fiber based materials.

Odor and Constituent Odorants of HDPE-Lignin Blends of Different Lignin Origin

The still-rising global demand for plastics warrants the substitution of non-renewable mineral oil-based resources with natural products as a decisive step towards sustainability. Lignin is one of the most abundant natural polymers and represents an ideal but hitherto highly underutilized raw material to replace petroleum-based resources. In particular, the use of lignin composites, especially polyolefin-lignin blends, is currently on the rise. In addition to specific mechanical property requirements, a challenge of implementing these alternative polymers is their heavy odor load. This is especially relevant for lignin, which exhibits an intrinsic odor that limits its use as an ingredient in blends intended for high quality applications. The present study addressed this issue by undertaking a systematic evaluation of the odor properties and constituent odorants of commercially available lignins and related high-density polyethylene (HDPE) blends. The potent odors of the investigated samples could be attributed to the presence of 71 individual odorous constituents that originated primarily from the structurally complex lignin. The majority of them was assignable to six main substance classes: carboxylic acids, aldehydes, phenols, furan compounds, alkylated 2-cyclopenten-1-ones, and sulfur compounds. The odors were strongly related to both the lignin raw materials and the different processes of their extraction, while the production of the blends had a lower but also significant influence. Especially the investigated soda lignin with hay- and honey-like odors was highly different in its odorant composition compared to lignins resulting from the sulfurous kraft process predominantly characterized by smoky and burnt odors. These observations highlight the importance of sufficient purification of the lignin raw material and the need for odor abatement procedures during the compounding process. The molecular elucidation of the odorants causing the strong odor represents an important procedure to develop odor reduction strategies.

Aroma-Active Compounds in Bartlett Pears and Their Changes during the Manufacturing Process of Bartlett Pear Brandy

Application of aroma extract dilution analysis to Bartlett pears and the fermented mash produced thereof revealed 24 and 34 aroma-active compounds in the flavor dilution (FD) factor range between 8 and 8192. Twenty-eight compounds, which have not been described before in Bartlett pears or in fermented pear mash, were identified. While ethyl (E,Z)-2,4-decadienoate (pear-like, metallic odor impression), hexyl acetate (green, fruity), and acetic acid (vinegar-like) showed the highest concentrations in Bartlett pears, ethanol (ethanolic), acetic acid, 3-methyl-1-butanol (malty), 1-hexanol (grassy, marzipan-like), (S)-2- and 3-methylbutanoic acid (sweaty), and 2-phenylethanol (flowery, honey-like) were present at the highest amounts in the fermented mash. The key aroma compounds were quantitated in each pear brandy production step (pears, fermented mash, distillate, and aged distillate) by stable isotope dilution analysis showing a clear influence of each step on the overall aroma of the spirit and, consequently, revealing clearly changing concentrations (e.g., of ethyl (S)-2-methylbutanoate, (E)-β-damascenone, ethyl (E,Z)-2,4-decadienoate, and ethyl (E,E)-2,4-decadienoate) and different aroma perceptions during the manufacturing process. In addition, the concentrations of the so-called "pear esters" ethyl (E,Z)-2,4-decadienoate and ethyl (E,E)-2,4-decadienoate were determined in 6 different pear varieties (Abate Fetel, Anjou, Bartlett, Forelle, Kaiser Alexander, and Packham's Triumph) clearly demonstrating the aroma potential of the variety Bartlett, which is mostly used for brandy production due to the high amounts of both esters eliciting a typical pear-like odor impression.

Characterization of the key aroma compounds in Bartlett pear brandies by means of the sensomics concept

The aroma compounds in two commercial Bartlett pear brandies clearly differing in their overall aroma profiles were detected in the volatile fractions by the aroma extract dilution analysis. In brandy A eliciting the more intense pear-like, fruity aroma, ethyl (S)-2-methylbutanoate, (E)-β-damascenone, 1,1-diethoxyethane, 2- and 3-methylbutanol, (S)-2- and 3-methylbutanoic acid, and 2-phenylethanol were found with the highest Flavor Dilution (FD) factors. In brandy B judged to have a weaker overall aroma, also (E)-β-damascenone, ethyl (S)-2-methylbutanoate, and 2-phenylethanol revealed high FD factors, while many odorants showed lower FD factors. Fourty-four odor-active compounds were quantitated by stable isotope dilution assays, and the odor activity values (OAVs; ratio of concentrations to odor thresholds) confirmed (E)-β-damascenone and ethyl (S)-2-methylbutanoate as important aroma compounds in brandy A, while the OAVs of most odorants were much lower in brandy B. By aroma recombination studies, the aromas of both brandies could be matched using reference odorants in the same concentrations as they occurred in the spirits. In 15 commercial Bartlett pear brandies ethyl (E,Z)-2,4-decadienoate and (E,E)-2,4-decadienoate eliciting a pear-like aroma showed a reasonable correlation of their concentrations with the overall aroma quality.

Occupational exposure to phenolic compounds at coke plants--urinary excretion of methoxyphenols as an indicator of exposure to methoxyphenols

OBJECTIVES

This study describes the exposure of coke plant workers to methoxyphenols. The relationship between exposure to methoxyphenols and urinary excretion of metabolites was examined.

METHODS

We determined concentrations of 2-methoxyphenol, 2-methoxy-4-methylphenol and 1-(4-hydroxy-3-methoxyphenyl)ethanone in the breathing-zone air and in the urine of workers, collected after the workshift. Urine metabolites were extracted after enzymatic hydrolysis by solid-phase extraction. Concentrations of methoxyphenols in air and urine were determined by gas chromatography with flame-ionization.

RESULTS

The time-weighted average concentrations (median) of methoxyphenols in the breathing zone air were as follows: 9.9 ng/m(3), 15.4 ng/m(3) and 92.5 ng/m(3) for 2-methoxyphenol, 2-methoxy-4-methylphenol and 1-(4-hydroxy-3-methoxyphenyl)ethanone, respectively. The median values of urinary concentrations were as follows: 582.5, 190.1, 235.0 and 21.8 µmol/mol creatinine for 2-methoxyphenol, 2-methoxy-4 methylphenol, 1-(4-hydroxy-3-methoxyphenyl)ethanone and 2,6-dimethoxyphenol, respectively. A statistically significant correlation between the exposure level and the urinary level was found for 2-methoxyphenol (r=0.573, p<0.01).

CONCLUSION

We found that the presence of 2-methoxyphenol in urine can be used as a biomarker for 2-methoxyphenol exposure. The analysis performed at the coke plant showed that the workers were exposed to relatively low concentrations of methoxyphenols.