Effect of blueberries addition during beer maturation on yeast metabolism

In recent years, there has been a significant interest in beverages with increased biological value, such as beer with blueberries. In this study, blueberries were added at the beginning of maturation of lager beer with an initial extract of 12, 14 and 16ºP. The effect of blueberries addition on yeast metabolism was investigated as concentration of ethanol, higher alcohols, esters, aldehydes, and vicinal diketones in the final beer were measured and compared to control samples without blueberries. The results showed that blueberries affected positively ethanol formation only when wort with initial extract of 12°P was used and had no significant effect when wort with higher extract was used. In regard to secondary metabolites, blueberries addition led to a decrease in higher alcohols concentration and an increase in esters amounts. All the carbonyl compounds (aldehydes and vicinal diketones) were higher in beer with blueberries.

The Different Hopping Methods Mathematical Models

Статья посвящена вопросу сравнения двух способов охмеления - классического и инновационного «холодного» способа внесения хмеля при дображивании пива, - а именно оценке основных факторов процесса, влияющих на интенсивность образования изоксантогумола, характеризующего тона горечи в пиве. Приведены результаты исследования качественных показателей модельных растворов, позволяющих минимизировать влияние прочих органических соединений на уровень содержания изоксантогумола в среде. Математическая оценка зависимостей позволила получить многофункциональные уравнения зависимости содержания изоксантогумола от ряда параметров, играющих важное значение при различных способах охмеления в технологии пивоварения. Математический анализ позволил выявить высокую достоверность полученных данных. Анализ полученных качественных характеристик в доверительном интервале р ≥ 0,95 позволил при классическом способе охмеления выявить влияние рН среды, а при «холодном» способе - живых дрожжевых клеток, преобразующих ксантогумол в изоформу. Основная часть полученных результатов согласовалась с ранее полученными относительно влияния рН, продолжительности охмеления, корреляции количества полифенолов, уровня изоксантогумола. Однако, влияние жизнедеятельности дрожжевых клеток не было отмечено ни в одном труде, что требует дополнительного экспериментального исследования. The article is devoted to the issue of comparing two hopping methods - the classical and innovative «dry hopping» method during the beer maturation, namely, the process main factors assessment that affect the isoxanthohumol formation intensity, which characterizes the beer bitterness tone. The model solutions qualitative indicators study results, which allow minimizing the effect of other organic compounds on the level of isoxanthohumol content in the medium, are presented. The dependences mathematical assessment made it possible to obtain multifunctional equations for the dependence of the isoxanthohumol content on several parameters that play an important role in various methods of hopping in brewing technology. Mathematical analysis made it possible to reveal the high reliability of the data obtained. The obtained qualitative characteristics analysis in the confidence interval p ≥ 0.95 made it possible to reveal the medium pH influence with the classical method of hopping, and with the «dry hopping» method - living yeast cells that convert xanthohumol into an isoform. Most of the results obtained were consistent with those previously obtained regarding the effect of pH, duration of hopping, and the correlation between the polyphenols amount and the isoxanthohumol level. However, the influence of the yeast cells vital activity was not noted in any work, which requires additional experimental research.