Journal of The Institute of Brewing最新文献

Use of non-conventional yeasts are increasingly seen as a option for the production of low and alcohol-free beers. In this study, the application of four non-conventional yeasts - Kazachstania servazzii, Kluyevoromyces marxianus, Pichia fermentans and Torulaspora delbrueckii, originally isolated from sourdough cultures, for cold contact fermentations was assessed by screening their ability to reduce wort aldehydes at a fermentation temperature of 1.0 ± 0.5°C. Of the evaluated yeasts, Torulaspora delbrueckii was found to be most promising, being capable of the removal of wort-derived aldehyde off-flavours, while being sufficiently sensitive to low temperatures to limit the formation of ethanol. Despite the different alcohol by volume (0.07% vs. 0.28%), the beers produced via cold contact fermentation at 10L scale with T. delbrueckii and a reference lager yeast strain were similar, with no major differences found after sensory analysis. The results suggest that T. delbrueckii could be used in cold contact fermentation to produce non-alcoholic beers with alcohol content at, or close to, 0%. © 2022 The Authors. Journal of the Institute of Brewing published by John Wiley & Sons Ltd on behalf of The Institute of Brewing & Distilling.

The effect of isomerised hop extract on the heat resistance of Saccharomyces cerevisiae BRYC 501 ascospores and Lactobacillus brevis BSO 566 was investigated. Heat resistance of yeast ascospores and L. brevis was determined in premium lager (4.5% ABV) and alcohol-free lager (0% ABV) at their initial bitterness and after adjustment with isomerised hop extract to 25 and 50 IBU. Results showed that D₆₀ of yeast ascospores in alcohol-free lager was reduced by >30% at 25 IBU and >50% at 50 IBU compared to lager with no added hop extract. In premium lager, D₆₀ was reduced by >10% at 25 IBU and >30% at 50 IBU. The addition of isomerised hop extract also had a significant impact on the z-values, which increased with higher concentrations of isomerised hop acids in both premium and alcohol-free lager. Slightly higher z-values were observed in premium lager (z = 4.0, 4.5 and 5.0°C for IBU = 6.3, 25 and 50 respectively) than in alcohol-free lager (z = 3.6, 4.0 and 4.2°C for IBU = 8.6, 25 and 50). The addition of isomerised hop extract also reduced the heat resistance of Lactobacillus brevis BSO 566. The findings in this study suggest that less bitter (low IBU) lagers should be pasteurised with higher pasteurisation units (PUs) than more bitter lagers (high IBU) which can be pasteurised at lower PUs. © 2022 The Institute of Brewing & Distilling

Beer inevitably changes due to an array of staling reactions. A major factor in beer ageing is the involvement of transition metals (iron, copper, manganese) in oxidative reactions. To tackle the flavour stability issue, metal chelation was investigated. Based on previous research, five primary chelators (tannic acid, gallic acid, EDTA, citric acid and phytic acid) were screened using experimental design for their capacity to reduce the content of wort transition metals. The chelating agents were added under varying conditions (mash out temperature, mash pH, grain bill, chelator concentration, addition time) during laboratory scale mashing to assess how they altered complexation and metal load. Fourteen alternative chelators (ferulic acid, tartaric acid, quercetin, chlorogenic acid and ten polyphenolic food extracts: green tea, pomegranate, grape seed, reishi, cinnamon, curcuma, milk thistle, ginkgo, grapefruit seed and raspberry) were also explored. Metal ions were analysed using inductively coupled plasma optical emission spectrometry and wort oxidative stability by electron spin resonance spectroscopy. Mash pH was the most decisive of all tested process variables: acidified mashing (pH 6 to 5) produced worts with more iron, manganese and zinc (230, 320 and 150%, respectively). Addition of effective chelators counteracted this undesirable effect for iron. Green tea extract, tannic acid and, particularly, pomegranate extract all resulted in lower wort iron. Conversely, addition of EDTA, caused iron, manganese and zinc to increase. Pomegranate extract (90% ellagic acid) was the best performing chelator and reduced radical generation in wort (80% reduction by 60 mg/L addition), making it a promising novel compound in the improvement of beer shelf life. © 2021 The Authors. Journal of the Institute of Brewing published by John Wiley & Sons Ltd on behalf of The Institute of Brewing & Distilling.

This study determined the impact of temperature on fermentation and sensory characteristics of imo-shochu, prepared at a laboratory scale by fermentation and distillation of moromi (a mixture of rice-koji, sweet potato and water). In accordance with the typical temperature regime used by shochu makers, the maximum temperature of moromi during fermentation was controlled at 25, 32, or 38°C. After distillation, the characteristics of the imo-shochu were determined by sensory evaluation and gas chromatography–mass spectrometry. In the moromi fermented at 25°C, the yeast population after fermentation was two-fold larger, but CO₂ productivity was 40% lower than when fermented at higher temperatures. Conversely, the concentration of acetic acid and amino acids were highest in the moromi fermented at 38°C. Shochu fermented at 25°C was rated as the fruitiest by sensory evaluation. It contained more esters (phenethyl acetate and ethyl caproate) and more higher alcohols and fatty acids. Shochu fermented at 38°C had the most acidic odour. This was consistent with the higher acetic acid levels in the moromi. Shochu fermented at 32°C had the sweetest and richest taste. Accordingly, fermentation temperature was found to be a critical factor for fermentative quality and flavour characteristics of imo-shochu. © 2021 The Institute of Brewing & Distilling

Cell immobilisation is the physical restriction of cells in a delimited region by means of physical and chemical approaches. It usually comprises a solid support containing cell biomass. In brewing fermentations, yeast cell immobilisation was widely explored during the 1970s to the 90s, with the expectation that immobilised systems would revolutionise the brewing industry. The most studied immobilisation method has been the attachment to a surface and entrapment within a porous solid. Some industrial applications were developed, but the flavour profile of the product rarely matched that produced by batch fermentation. Numerous factors are important in immobilised yeast systems and its successful industrial implementation. Although cell immobilisation results in many advantages, such as high biomass loading and ease of cell reuse, there are drawbacks including physiological changes and mass transfer limitations. Therefore, in order to design a feasible brewing fermentation process using immobilised yeast cells, the solid support, immobilisation method and the bioreactor system require to be properly developed. In this review, yeast cell immobilisation technology in brewing is considered together with methods of immobilisation with the associated advantages and drawbacks. Physiological and metabolic alterations in yeast are also explored and industrial applications are highlighted. It is suggested that immobilisation technology has new opportunities as the market is increasingly open to novel flavours and styles. © 2021 The Institute of Brewing & Distilling

The spoilage of six alcohol-free (AFB, ≤ 0.05% ABV) and two low alcohol beers (LAB, ≤ 1.2% ABV) was assessed by challenge testing with microflora from draught beer. Spoilage of AFB and LABs was greater (2-5 x) than two ‘control’ premium lager beers (4.5% ABV). Measurement of spoilage by challenge testing was reproducible irrespective of the source of draught beer microflora (public house, date, or beer style). Spoilage was correlated with the level of ‘fermentables’ (glucose + fructose + maltose) in the product but was also dependent on the availability of micronutrients. The addition of ethanol (2-8% ABV) to three AFBs and a LAB resulted only in a modest inhibition of spoilage (collectively 24% at 8% ABV) and, it is suggested, that the complexity of the product composition provides protection. Given the vulnerability of AFBs and LABs to spoilage and susceptibility to microorganisms that are usually supressed by ethanol, it is strongly recommended that low or alcohol-free beer styles are not offered to consumers in the on-trade by conventional long line dispense systems. It is suggested that AFB and LABs in a draught format require innovative, hygienically designed stand-alone dispense systems that remove or significantly minimise the risk of microbiological contamination, growth and associated product spoilage. © 2021 The Institute of Brewing & Distilling

Chinese Baijiu is one of the six major distilled spirits in the world, occupying an important place in the global spirits industry due to its unique brewing technology, special taste and flavour. Historically, Baijiu has evolved into twelve flavour types, among which the Moutai-flavour, Luzhou-flavour, and Light-flavour are the main types consumed in China. However, the profiles of the three flavour types of Baijiu have not been summarised and considered systematically. Here, we review the characteristics of the three main flavour types of Baijiu and discuss the key flavour components (description, odour threshold, and odour activity value), together with research advancements. Furthermore, areas where further research in Chinese Baijiu flavour is required are discussed. © 2021 The Institute of Brewing & Distilling