Journal of The Institute of Brewing最新文献

In the spirits industry, understanding the behaviour of volatile flavouring compounds (congeners) during distillation is important. This simulation study with the ProSim software®, BatchColumn, investigates the influence of different parameters of a multi-stage batch distillation on 57 congeners from five chemical families (alcohols, aldehydes, esters, acids, and terpenes). Industrial and laboratory scale whisky distillations were conducted with a fermented malted barley mash. The simulations illustrated the behaviour of volatile compounds based on how their volatility varied with ethanol concentration. The distribution of compounds between the different fractions (head, heart, tail and residue) was calculated. Further, optimisation strategies for the industrial distillation were tested by simulation. These included (1) cutting distillation later (ethanol mass fraction of 0.061 instead of 0.105) as the recovery of pleasant compounds is small compared to that of acids; (2) choosing an ethanol mass fraction during the heart extraction around 0.60 (67% v/v), rather than 0.67 (75% v/v) as it increases the recovery of compounds of interest and decreases the duration of distillation and energy costs and (3) enabling a higher concentration of ethanol at the beginning of the distillation to obtain better separation of aldehydes and esters. © 2022 The Authors. Journal of the Institute of Brewing published by John Wiley & Sons Ltd on behalf of The Institute of Brewing & Distilling.

Premature yeast flocculation (PYF) is a sporadic problem in brewery fermentations that results in the incomplete utilisation of fermentable sugars. This work tests the hypothesis that barley or malt infected by xylanase-producing filamentous fungi contributes to premature yeast flocculation. Ten different fungi and yeasts were isolated and identified from malt and barley husk. These were inoculated onto barley husk and xylanase activity, arabinoxylan and the PYF value determined. The results from the fungal strains - Aureobasidium pullulans, Aspergillus flavus, Fusarium graminearum, and Alternaria tenuissima – indicated involvement in PYF. Small-scale malting and brewing was used to evaluate the PYF activity of fungal infected barley. The results showed that xylanase activity and arabinoxylan content were significantly (p < 0.05) related to PYF activity. With the exception of F. graminearum, xylanase activity was detected in the three other fungal isolates. The xylanases reduced the minimum concentration of arabinoxylan required for the induction of PYF. A small-scale brewing assay showed that xylanase secreted by the four filamentous fungi played a role in PYF. This research will contribute to the development of effective control strategies to prevent PYF factors in malt. © 2022 The Institute of Brewing & Distilling.

Extraction of proteins from industrial residues is a potential source for animal feed. Alkaline extraction combined with isoelectric precipitation may be a useful method for isolating protein from brewer’s spent grain (BSG), an abundant by-product from the brewing industry. The objective of this study was to examine the effect of temperature (30, 45 and 60°C), time (30, 60, 120 and 180 minutes), agitation (shaking and stirring), precipitation salinity (0.5 M sodium chloride), isolation mode (freeze drying and precipitation), pre-treatment (defatting and delignification) and repeated extraction on the protein yield and protein content from BSG. Generally, the protein content decreased while protein yield increased with increasing extraction temperatures. Yield and content were maximised after 30 minutes reaching the highest protein content at 30^oC (54.8%) and the highest protein yield at 60^oC (10.5%). Precipitation with 0.5 M sodium chloride reduced the protein content to 36.4% and the yield to 4.2%. Freeze drying combined with triple extraction yielded a protein content of 20-25%, together with a relatively high protein yield (ca. 45-50%). Delignification increased the protein content from 27% to 32% whereas defatting reduced the overall protein yield from 45% to 38%. Combining isoelectric precipitation and single extraction was associated with a higher protein content (40-55%) but poor protein yields (5-10%). In the light of these findings, further research is required to establish conditions that maximise both the protein content and yield. © 2022 The Institute of Brewing & Distilling.

Top-fermented wheat beers are known for their unique aroma. However, the impact of speciality wheat malts on the aroma of these beers and the transfer of odour active compounds from malt to the beer has not been investigated in detail. Three beers were brewed with different malt composition. The grist for each beer contained 50% kilned barley malt and 50% different wheat malts - beer (1) kilned wheat malt, beer (2) kilned wheat malt and caramel wheat malt, and beer (3) kilned wheat malt and roasted wheat malt. The odour active compounds in the beers were identified by aroma extract dilution analysis and their individual impact on aroma was evaluated by quantitation and calculation of odour activity values (OAVs). The results were verified sensorially by comparing aroma reconstitution models with the original beers. Characteristic odour active compounds in the beer brewed with caramel wheat malt were earthy compounds 2-ethyl-3,5-dimethylpyrazine, 2-ethyl-3,6-dimethylpyrazine, 2,3-diethyl-5-methylpyrazine, caramel-like compounds 4-hydroxy-2,5-dimethylfuran-3(2H)-one and maltol, and sotolon with a soup seasoning-like aroma. The aroma of the roasted wheat malt beer was characterised by smoky and phenolic compounds 2-methoxyphenol and 4-methylphenol. Important beer odorants were quantified in the malts to assess their transfer from malt to beer. The results suggest that direct transfer of the odour active compounds in beers was not significant and that they were formed and/or released during the brewing process, confirming earlier results with different barley malts and bottom-fermented beers. © 2022 The Authors. Journal of the Institute of Brewing published by John Wiley & Sons Ltd on behalf of The Institute of Brewing & Distilling.

Beer inevitably changes over time: the colour will darken, haze may form, and stale flavours develop, while others fade. The challenge of maintaining the fresh flavour quality of beer (over a typical 9-12 month storage period) is generally the determining factor of a beer's shelf-life for brewers, as opposed to colloidal or microbiological stability. Fortunately, as early as the brewhouse, oxidative degradation can - to a certain extent - be controlled, enabling the shelf-life to be increased. This review considers the general issues of oxidative stability, mechanisms of ageing, ways of quantifying staleness and staling potential, and current practical approaches to prevent oxidative beer ageing. Emphasis is placed on the catalytic role of iron, copper and manganese on oxidation during brewing and storage; and how the removal and/or inhibition of these prooxidative transition metal ions leads to prolonged beer (flavour) stability.

Flavour instability of beer is a concern for brewers and has been investigated over many decades. Despite advancements in the characterisation of changes during the ageing process of pale lager beers (PLB), research on the flavour instability of non-alcoholic beer (NAB) - a beer style becoming increasingly prevalent on the market - is lacking. This study characterises the main chemical-analytical changes during a forced ageing process (90 days at 30°C) of seven commercially available NAB and compares the findings to the aged seven PLB counterparts. The major differences from ageing were increased concentrations of aldehydes and decreased levels of glutamine and esters, which occurred to the same extent for both beer styles. However, trans-iso-α-acids underwent a greater decrease in aged NAB, likely due to the lower pH of this style. Furthermore, correlations between ageing parameters in aged and fresh beers, previously found in PLB (Strecker aldehydes and corresponding amino acids, relative decrease of trans-iso-α-acids and pH) are confirmed and were also valid in NAB. Interestingly, sensory analysis revealed that aged NAB showed lower overall ageing scores, compared to aged PLB. This might be explained by differences in the formation of aldehydes causing worty off-flavours during ageing. In summary, this study provides a detailed overview of the ageing process of non-alcoholic beers in comparison with pale lager beers, which could help brewers to develop more flavour stable beers. © 2022 The Institute of Brewing & Distilling.