High Gravity Wort Fermentations Research Articles

Comparison of the hydrocolloids application efficiency for stabilizing the foam of beer

Subject of research: technology of high gravity brewing, developed to improve production efficiency and reduce energy consumption. This technology has a wide range of benefits, from improving process economics to reducing environmental impact.
 Investigated problem: despite the presence of significant advantages, there are a number of problems in the technology of high gravity brewing that need to be solved. The main problem is to reduce the foam stability of the resulting beer, which, together with the appearance, aroma and taste, is the most important attributes of the quality of the beverage for the consumer.
 The stability and texture of the foam depend, among other things, on the quality of grain and hop raw materials, and the course of technological processes. Elevated levels of key malt proteins (LTP1, Z4 and Z7) and hop α-acids have a positive effect on foam quality. Yeast protease A has a negative effect. Yeast secretes this enzyme to a greater extent during fermentation of high gravity wort, which may be one of the reasons for the decrease in foam stability in high gravity brewing.
 High molecular weight a- and b-glucans with hydrophilic properties can play an important role in foam stabilization. They increase the viscosity of the liquid, slow down its drainage from the foam segments and thereby increase the foam retention.
 Main scientific results: the effect of hydrocolloids (highly methoxylated pectin, carboxymethyl cellulose, xanthan gum, guar gum, a mixture of xanthan and guar gum) on foam performance and beer filtration rate was investigated. The advantages of pectin as an additive allowing to stabilize beer foam, in particular, in high gravity - brewing, have been established. The recommended dosage of the additive is 0.4-1 g/hl. Highly methoxylated pectin is a good alternative to the currently widespread use of propylene glycol alginate.
 The area of practical implementation of the research results: brewing companies.
 Innovative technological product: highly methoxylated pectin as a stabilizing additive for beer foam.
 Scope of application of the innovative technological product: the use of highly methoxylated pectin as additives that stabilize beer foam, in particular in high gravity brewing.

Вплив температури на зброджування високогустинного сусла

Значне збільшення вартості енергоресурсів сприяло розвитку сучасних енергоощадних технологій. Для виготовлення пива затрачається велика кількість енергії та теплоносіїв на стадії приготування сусла та холодоагентів на стадії бродіння. В умовах енергетичної кризи та великої конкуренції серед виробників виникає потреба запроваджувати нові, енергоощадні технології, зокрема високогустинне пивоваріння. Потенційні переваги технології високогустинного пивоваріння над звичайною технологією включають також значну економію води, більшу кількість спирту і зниження витрат енергії та праці, менші капітальні витрати. Проте, переваги високогустинного пивоваріння стають очевидними, коли тривалість бродіння залишається помірною, а життєздатність дріжджів та смак пива є адекватними. Ці показники в значній мірі залежать від параметрів процесу головного бродіння, зокрема від температури. В роботі досліджено вплив температури головного бродіння 9, 12, 15 і 18 °С на зброджування високогустинного сусла концентрацією 16% сухих речовин та фізіологічні властивості дріжджів. Для досліджень використовували дріжджі низового бродіння раси W-34/70. Тривалість бродіння становила 9 діб. Встановлено, що при традиційній температурі бродіння 9 °С процес відбувається повільно та припиняється передчасно. Проведення бродіння при 18 °С дозволяє досягти високого ступеня зброджування, проте погіршуються фізіологічні властивості дріжджів, зокрема знижується вміст клітин з глікогеном та погіршуються флокуляційні властивості дріжджів. Температура бродіння практично не впливала на вміст нежиттєздатних дріжджових клітин. Проте їх кількість була дещо вищою від значення, якого дотримуються на пивоварних підприємствах, що зумовлено впливом осмотичного та етанольного стресу. Оптимальна температура головного бродіння повинна знаходитись в межах 12–15 °С. За цих значень температур досягається висока бродильна активність дріжджів, ступінь зброджування пива та зберігаються хороші фізіологічні властивості дріжджів, а вміст віцинальних дикетонів не перевищує гранично-допустимої концентрації для молодого пива.

Зниження вмісту віцинальних дікетонів при зброджуванні високогустинного сусла

Одним із завдань високогустинного пивоваріння як сучасної енергоощадної технології є отримання пива високої якості, адже смак і аромат напою ‒ його головні споживчі властивості. Віцинальні дікетони ‒ діацетил (2,3-бутандіон) та 2,3-пентандіон – відіграють значну роль у формуванні смаку. Завдання пивоварів полягає в зведенні до мінімуму їх утворення або пришвидшенні їх відновлення до речовин із вищим порогом відчуття. До основних методів зниження вмісту дікетонів належать оптимізація параметрів бродіння та дозрівання, використання модифікованих штамів дріжджів та іммобілізованих дріжджових клітин. Цього досягають також застосуванням ферменту α-ацетолактатдекарбоксилази, який міститься в ферментному препараті Матурекс. Він каталізує реакцію перетворення α-ацетолактату безпосередньо в ацетоїн, минаючи утворення діацетилу. Таким чином значно знижується вміст дікетонів у пиві та скорочується тривалість його дозрівання. В роботі досліджено вплив параметрів зброджування високогустинного сусла – концентрації сухих речовин у суслі, температури та тривалості процесу на вміст дікетонів у пиві. Визначено оптимальні умови головного бродіння: концентрація сусла 16% сухих речовин, температура бродіння 15 °С, тривалість 7 діб. Встановлено вплив дози ферментного препарату Матурекс 1, 2 і 3 г на 1 гл сусла на вміст віцинальних дікетонів у молодому пиві. Визначено оптимальну дозу препарату, яка становить 2 г на 1 гл сусла. Досліджено вплив ферментного препарату Матурекс на фізико-хімічні показники молодого та готового пива – вміст екстракту та етанолу, рН і кислотність, вміст віцинальних дікетонів. Таким чином, для пришвидшення процесів дозрівання пива в технології високогустинного пивоваріння, зниження вмісту віцинальних дікетонів у пиві та збільшення ефективності виробництва можна рекомендувати зброджування сусла концентрацією 16% сухих речовин при температурі 15 °С впродовж 7 діб з додаванням ферментного препарату Матурекс у кількості 2 г на 1 гл сусла.

Saccharomyces cerevisiae in the Production of Whisk(e)y

Whisk(e)y is a major global distilled spirit beverage. Whiskies are produced from cereal starches that are saccharified, fermented and distilled prior to spirit maturation. The strain of Saccharomyces cerevisiae employed in whisky fermentations is crucially important not only in terms of ethanol yields, but also for production of minor yeast metabolites which collectively contribute to development of spirit flavour and aroma characteristics. Distillers must therefore pay very careful attention to the strain of yeast exploited to ensure consistency of fermentation performance and spirit congener profiles. In the Scotch whisky industry, initiatives to address sustainability issues facing the industry (for example, reduced energy and water usage) have resulted in a growing awareness regarding criteria for selecting new distilling yeasts with improved efficiency. For example, there is now a desire for Scotch whisky distilling yeasts to perform under more challenging conditions such as high gravity wort fermentations. This article highlights the important roles of S. cerevisiae strains in whisky production (with particular emphasis on Scotch) and describes key fermentation performance attributes sought in distiller’s yeast, such as high alcohol yields, stress tolerance and desirable congener profiles. We hope that the information herein will be useful for whisky producers and yeast suppliers in selecting new distilling strains of S. cerevisiae, and for the scientific community to stimulate further research in this area.

Production of ethanol through the fermentation of high-gravity wort obtained using ultradispersed grain raw materials

Production of ethanol through the fermentation of high-gravity wort obtained using ultradispersed grain raw materials

Effect of Mineral Ion Addition on Yeast Performance during Very High Gravity Wort Fermentation

Effect of Mineral Ion Addition on Yeast Performance during Very High Gravity Wort Fermentation

Monitoring yeast physiology during very high gravity wort fermentations by frequent analysis of gene expression

Brewer's yeast experiences constantly changing environmental conditions during wort fermentation. Cells can rapidly adapt to changing surroundings by transcriptional regulation. Changes in genomic expression can indicate the physiological condition of yeast in the brewing process. We monitored, using the transcript analysis with aid of affinity capture (TRAC) method, the expression of some 70 selected genes relevant to wort fermentation at high frequency through 9-10 day fermentations of very high gravity wort (25 degrees P) by an industrial lager strain. Rapid changes in expression occurred during the first hours of fermentations for several genes, e.g. genes involved in maltose metabolism, glycolysis and ergosterol synthesis were strongly upregulated 2-6 h after pitching. By the time yeast growth had stopped (72 h) and total sugars had dropped by about 50%, most selected genes had passed their highest expression levels and total mRNA was less than half the levels during growth. There was an unexpected upregulation of some genes of oxygen-requiring pathways during the final fermentation stages. For five genes, expression of both the Saccharomyces cerevisiae and S. bayanus components of the hybrid lager strain were determined. Expression profiles were either markedly different (ADH1, ERG3) or very similar (MALx1, ILV5, ATF1) between these two components. By frequent analysis of a chosen set of genes, TRAC provided a detailed and dynamic picture of the physiological state of the fermenting yeast. This approach offers a possible way to monitor and optimize the performance of yeast in a complex process environment.

The Yeast Vacuole -A Scanning Electron Microscopy Study During High Gravity Wort Fermentations

The yeast vacuole has been shown to exhibit morphological responses to environmental conditions when exposed to worts of different gravity during fermentation. Marked effects of high gravity wort (20° Plato) on yeast morphology compared to more conventional wort gravity (12° Plato) were observed. High gravity worts caused vacuolar enlargement compared to conventional gravity wort. These results suggested that yeast cells experienced severe alterations with the vacuolar tonoplast when exposed to high osmotic pressure and elevated levels of ethanol.

α-グルコシダーゼを利用したビールの高濃度醸造 (第4報)

High gravity brewing has come to be widely used for increased brewery efficiency. However, it is not easy to maintain good yeast performance during fermentation because of the stress on yeastcaused by high sugar and/or ethanol concentrations. Therefore, sugar attenuation tends to be insufficientand the finished beer contains high concentrations of acetic acid and esters.We previously reported on the development of a new fermentation method by which severaldifficulties in high gravity brewing could be overcome. In this method, α-glucosidase added at thebeginning of fermentation enables the conversion of wort sugars by glycosyl-transfer and hydrolyticreactions to proceed in parallel with ethanol formation by yeast. By using α-glucosidase, we succeededin high gravity brewing with a top fermentation brewer's yeast at a constant fermentation temperatureof 15°. However, bottom fermenting brewer's yeast is more widely used for commercial brewing aroundthe world. In this paper we report results of using the method with bottom fermenting brewer's yeast. We confirmed that the method could be successfully applied to high gravity wort fermentation withbottom fermenting yeast at low temperature. When α-glucosidase was added to 20% Plato wort at aconcentration of 800mg/l, the wort was successfully fermented at 10° with a bottom fermenting brewer's yeast, W 34/70. The real degree of fermentation was 77%, which was 16% higher than that ofthe control fermentation, and the concentration of acetic acid was 200mg/l, which was 85mg/l lowerthan that of the control. The addition of α-glucosidase was also effective for increasing the degree offermentation of dextrinous wort. When α-glucosidase was added at the concentration of 400mg/l to 20% Plato wort containing 6.2% dextrin, the content of dextrin decreased to 3.7% by the end of fermentationwith a top fermenting brewer's yeast, NCYC 1245; the real degree of fermentation was 75%, whichwas 19% higher than that of the control. It is suggested that the use of α-glucosidase is applicable forbrewing good beers from wort that have a low proportion of fermentable sugars, meaning that malt withlower diastatic power could be utilized. The use of enzymes in fermentation would open several newpossibilities to add to existing enzyme methods, such as the use of acetolactate decarboxylase to shortenthe conditioning period or glucoamylase for dry beer brewing.

Improvement of the ethanol productivity in a high gravity brewing at pilot plant scale.

A 23 full factorial design was used to study the influence of different experimental variables, namely wort gravity, fermentation temperature and nutrient supplementation, on ethanol productivity from high gravity wort fermentation by Saccharomyces cerevisiae (lager strain), under pilot plant conditions. The highest ethanol productivity (0.69 g l(-1) h(-1)) was obtained at 20 degrees P [degrees P is the weight of extract (sugar) equivalent to the weight of sucrose in a 100 g solution at 20 degrees C], 15 degrees C, with the addition of 0.8% (w/v) yeast extract, 24 mg l(-1) ergosterol and 0.24% (v/v) Tween 80.

Changes in the yeast metabolism at very high-gravity wort fermentation.

The rate of ethanol production increased with increasing wort gravity up to the initial wort concentration of 24%, reaching the maximum ethanol concentration of 6.2%, but its attenuation reached only 49%. The intracellular trehalose accumulation was proportional to the initial wort gravity, at 24 or 30% wort fermentation increased 3 or 4.5 times, respectively, compared to 12% wort fermentation. Trehalose accumulation began after exhaustion of glucose, ceased after uptake of approximately 65% reducing saccharides, despite of increasing ethanol or remaining saccharide concentration in the environment.

Very high gravity wort fermentation by immobilised yeast

Using calcium alginate-entrapped yeast, 24% (w/w) wort was successfully fermented within 8 days. This is half the time needed for fermentation by free yeast. The highest ethanol concentration obtained was 10.5% (v/v). When the original wort gravity was increased, the specific rate of ethanol production remained constant 0.16 g gh−1 and the viability did not fall bellow 95% of living cells. Protection of cell against osmotic stress by gel matrix was also confirmed by trehalose measurement. The maximum intracellular trehalose content in calcium alginate-entrapped yeast was 3 times lower compared to free yeast at 30% (w/w) wort fermentation.

Effects of heat shock and ethanol stress on the viability of aSaccharomyces uvarum (carlsbergensis) brewing yeast strain during fermentation of high gravity wort

The effects of heat shock and ethanol stress on the viability of a lager brewing yeast strain during fermentation of high gravity wort were studied. These stress effects resulted in reduced cell viability and inhibition of cell growth during fermentation. Cells were observed to be less tolerant to heat shock during the fermentation of 25°P (degree Plato) wort than cells fermenting 16°P wort. Degree Plato (oP) is the weight of extract (sugar) equivalent to the weight of sucrose in a 100 g solution at 20°C. Relieving the stress effects of ethanol by washing the cells free of culture medium, improved their tolerance to heat shock. Cellular changes in yeast protein composition were observed after 24 h of fermentation at which time more than 2% (v/v) ethanol was present in the growth medium. The synthesis of these proteins was either induced by ethanol or was the result of the transition of cells from exponential phase to stationary phase of growth. No differences were observed in the protein composition of cells fermenting 16°P wort compared to those fermenting 25°P wort. Thus, the differences in the tolerance of these cells to heat shock may be due to the higher ethanol concentration produced in 25°P wort which enhanced their sensitivity to heat shock.

Effect of the Timing of Oxygenation on Very High Gravity Brewing Fermentations

Yeasts require small quantities of oxygen to synthesize unsaturated fatty acids and sterols. As the fermentation rate is proportional to the number of metabolically active yeasts present, rapid wort attenuation is therefore related to the availability of oxygen. The effects of limited oxygen supply are compounded in high gravity or very high gravity wort fermentations. The objective was to ascertain the optimal supply time, postinoculation, that would give the most rapid attenuation. The practical extensions of the research are discussed with relevance to current industrial practice

Considerations—The Fermentation of High-Gravity Wort

Corn and barley syrups manufactured in different ways varied in fermentability. Tendencies observed with conventional or low-gravity worts were usually accentuated at starter solids of 18° P and gr...