Вплив концентрації сусла на стадії культивування дріжджів на зброджування висококонцентрованого пивного сусла

Abstract

Досліджено вплив концентрації сусла 10, 12, 14, 16 та 18% сухих речовин на стадії культивування дріжджів на їх фізіологічний стан і біомасу клітин, динаміку зброджування висококонцентрованого пивного сусла та фізико-хімічні показники молодого пива. Визначено оптимальний діапазон концентрації поживного середовища, який становить 10–12% сухих речовин.

One of the current methods of energy saving technologies is high gravity brewing. Unfavourable conditions are observed during fermentation of highly concentrated wort for the yeast nutrition and flow of fermentation process. In addition, the alcohol content of more than 5% vol. inhibits yeast viability. Negative reaction to osmotic stress can be reduced by gradually adaptation of cells to a high concentration of solids ranging starting from stage of yeast cultivation. Therefore, the purpose of our research was to study the influence of the concentration of nutrient medium during cultivation process on the physiological properties of yeast and fermentation of highly concentrated beer wort. The concentration of the culture medium at the stage of cultivation greatly influences the physiological state of yeast. It is established, that the increase of concentration leads to the increase in the proportion of dead yeast cells, especially in the dry matter content of 16 and 18%. Reserve substances determine physiological state of yeast culture, have a direct impact on the fermentation and involved in maintaining of cell viability in response to stress factors. Increasing the concentration of the culture medium almost has no effect on the accumulation of glycogen in cells on the first and on the second stages of cultivation. On the third stage increase in the proportion of mature cells with increasing concentrations of the culture medium is observed. Environmental conditions greatly affect the growth and reproduction of the yeast. Increasing of concentration of the culture medium from 10 to 16% led to an increase in the concentration of yeast cells and slight decrease of relative biomass (for 7-16,6%). Relative biomass significantly decreased (by 34.9%) when the content of solids is 18%. Therefore, it is inappropriate to use nutrient medium with concentration of 18% solids at a stage of culturing yeast for high gravity brewing. Fermentative activity is an important technological feature of yeast. It is established, that increase of the concentration of the culture medium from 10 to 16% at the stage of culturing yeast led to decrease in the rate of fermentation obtained by seeding yeast, to the reduction of ethanol concentration in young beer, to the increase of the extract in young beer and to reduction of the extract fermentation rate. Consequently, the use of a more concentrated nutrient medium at the cultivation stage allows to get seeding yeast with lower fermentation activity. This is caused by the decrease in their rate of growth and reproduction, deterioration of physiological state of yeast, decrease in the concentration of viable cells. Beer taste profile is formed particularly by vicinal dike tones. Their content in young beer grew and organoleptic properties of beer are respectively deteriorated by means of seeding yeast, cultured in a more concentrated nutrient media. Thus, the optimal range of concentration of the culture medium at the stage of cultivation of brewer's yeast for high gravity brewing is 10–12% dry matter.