Determination of optimal sample preparation for aldehyde extraction from pale malts and their quantification via headspace solid-phase microextraction followed by gas chromatography and mass spectrometry.

Aldehydes originating from malt play an important role in beer flavour deterioration. In order to better understand the influence of malting process on beer staling, it is necessary to acquire a reliable analytical methodology for determination of beer staling aldehydes in malt. Therefore, the aim of this study was to evaluate extraction parameters, which allow quantification of beer staling aldehydes present in pale malts.

Flax treatment with strategic enzyme combinations: Effect on chemical fiber composition and ease of fiber extraction.

The effect of treatment of flax with strategic enzyme combinations on the ease of fiber extraction and the chemical fiber composition is reported in this study. To contribute to the increasing demand for bio-based and sustainable materials, it is of great importance to develop optimal enzyme formulations which can replace the yet poorly controlled traditional dew retting process. Regarding the chemical composition of the fiber, enzymatic treatments all resulted in similar improvements, with an enhanced cellulose content of 81 ± 1% after polygalacturonase + xylanase treatment (vs.

Enzymatic treatment of flax for use in composites.

Enzymes are highly advantageous compared to dew retting to reach fibers of high and consistent quality. However, no unambiguous insights have been retained from the research, i.e.

Phenotypic landscape of non-conventional yeast species for different stress tolerance traits desirable in bioethanol fermentation.

Background: Non-conventional yeasts present a huge, yet barely exploited, resource of yeast biodiversity for industrial applications. This presents a great opportunity to explore alternative ethanol-fermenting yeasts that are more adapted to some of the stress factors present in the harsh environmental conditions in second-generation (2G) bioethanol fermentation. Extremely tolerant yeast species are interesting candidates to investigate the underlying tolerance mechanisms and to identify genes that when transferred to existing industrial strains could help to design more stress-tolerant cell factories.

Fermentation assays reveal differences in sugar and (off-) flavor metabolism across different Brettanomyces bruxellensis strains.

Brettanomyces (Dekkera) bruxellensis is an ascomycetous yeast of major importance in the food, beverage and biofuel industry. It has been isolated from various man-made ecological niches that are typically characterized by harsh environmental conditions such as wine, beer, soft drink, etc. Recent comparative genomics studies revealed an immense intraspecific diversity, but it is still unclear whether this genetic diversity also leads to systematic differences in fermentation performance and (off-)flavor production, and to what extent strains have evolved to match their ecological niche.

A large set of newly created interspecific Saccharomyces hybrids increases aromatic diversity in lager beers.

Lager beer is the most consumed alcoholic beverage in the world. Its production process is marked by a fermentation conducted at low (8 to 15°C) temperatures and by the use of Saccharomyces pastorianus, an interspecific hybrid between Saccharomyces cerevisiae and the cold-tolerant Saccharomyces eubayanus. Recent whole-genome-sequencing efforts revealed that the currently available lager yeasts belong to one of only two archetypes, "Saaz" and "Frohberg.

Changes in the hop-derived volatile profile upon lab scale boiling.

Hop terpenes might be oxidized during kettle boiling into more water soluble compounds that could contribute to 'hoppy' aroma of kettle hopped lager beers. Our current research proves that the boiling process induces significant changes in the hop oil volatile profile. The discrimination between volatile profiles of unboiled and boiled hop essential oil was evaluated via principal component and cluster analysis (PCA and CA).

Phenotypic evaluation of natural and industrial Saccharomyces yeasts for different traits desirable in industrial bioethanol production.

Saccharomyces cerevisiae is the organism of choice for many food and beverage fermentations because it thrives in high-sugar and high-ethanol conditions. However, the conditions encountered in bioethanol fermentation pose specific challenges, including extremely high sugar and ethanol concentrations, high temperature, and the presence of specific toxic compounds. It is generally considered that exploring the natural biodiversity of Saccharomyces strains may be an interesting route to find superior bioethanol strains and may also improve our understanding of the challenges faced by yeast cells during bioethanol fermentation.

Characterization of novel single-variety oxygenated sesquiterpenoid hop oil fractions via headspace solid-phase microextraction and gas chromatography-mass spectrometry/olfactometry.

The volatile composition of novel varietal oxygenated sesquiterpenoid hop oil fractions ("spicy essences") was characterized by headspace solid-phase microextraction in combination with gas chromatography-mass spectrometry. Oxygenated sesquiterpenes represent the major chemical compound class, accounting for at least 65% of the total volatile fraction. In addition to oxygenated sesquiterpenes, spicy hop essences consist of several ketones, sesquiterpene and monoterpene hydrocarbons, and a relatively high number of unidentified compounds.

Assessing the xylanolytic bacterial diversity during the malting process.

The presence of microorganisms producing cell wall hydrolyzing enzymes such as xylanases during malting can improve mash filtration behavior and consequently have potential for more efficient wort production. In this study, the xylanolytic bacterial community during malting was assessed by isolation and cultivation on growth media containing arabinoxylan, and identification by 16S rRNA gene sequencing. A total of 33 species-level operational taxonomic units (OTUs) were found, taking into account a 3% sequence dissimilarity cut-off, belonging to four phyla (Actinobacteria, Bacteroidetes, Firmicutes and Proteobacteria) and 25 genera.

Characterization of novel varietal floral hop aromas by headspace solid phase microextraction and gas chromatography-mass spectrometry/olfactometry.

In this study, headspace solid phase microextraction (HS-SPME) and gas chromatography-mass spectrometry (GC-MS) were optimized and implemented to investigate the volatile composition of novel floral hop essences prepared from four German aroma hop varieties. In total, 91 different constituents were assigned, which were further grouped into monoterpene hydrocarbons, esters, ketones, aldehydes, furans, and oxygenated and nonoxygenated sesquiterpenes. Most volatiles belong to the ester group, whereas the monoterpene hydrocarbon β-myrcene appears to be the predominant compound in all hop oil preparations investigated.

On the origin of free and bound staling aldehydes in beer.

The chemistry of beer flavor instability remains shrouded in mystery, despite decades of extensive research. It is, however, certain that aldehydes play a crucial role because their concentration increase coincides with the appearance and intensity of "aged flavors". Several pathways give rise to a variety of key flavor-active aldehydes during beer production, but it remains unclear as to what extent they develop after bottling.

A kinetic study on the isomerization of hop alpha-acids.

In this article, a detailed study on hop alpha-acid isomerization kinetics is presented. Because of the complex wort matrix and interfering interactions occurring during real wort boiling (i.e.