Search

Background: In recent years, increasing health awareness in consumers has motivated breweries to expand their beverage ranges with products with increased biological value. The aim of the present research was to develop probiotic wort-based beverages with grapefruit or tangerine zest essential oil addition., Methods: Wort was produced with 60% Pilsen malt, 20% Vienna malt and 20% Caramel Munich ІІ malt with and without the addition of 0.05% (v/v) grapefruit or tangerine essential oils. It was inoculated with the probiotic yeast strain Saccharomyces cerevisiae var. boulardii Y1. Fermentations were carried out at a constant temperature of 10°C for 5 days. The dynamics of the extract, the alcohol content and the concentration of viable cells were monitored daily. The total phenolic content, phenolic acid and flavonoid phenolic compounds were determined because of their antioxidant activity. The antioxidant activity was determined by radical scavenging assay (DPPH) and ferric reducing antioxidant power (FRAP). A descriptive organoleptic evaluation of the final beverages was performed., Results: The essential oils inhibited yeast growth to some extent at the beginning of the fermentation, even at a concentration of 0.05% (v/v), which resulted in lower alcohol content in the beverages with essential oil addition. Nevertheless, at the end of fermentation the concentration of viable cells was almost equal in all the beverages. Tangerine essential oil addition led to the highest content of phenolics, of which phenolic acids predominated. Therefore, the highest antioxidant activity of the beverage with tangerine essential oil can be ascribed to phenolic acids. The results of the sensorial evaluation also showed that the panel had preference towards the beverage with tangerine essential oil., Conclusions: The combination of essential oil and the probiotic yeast strain resulted in beverages with higher biological value than the beverages produced with the probiotic strain alone. The results obtained will be used for optimisation of process variables in the production of pilot-scale wort-based probiotic beverages with essential oil addition.

The combination of modified mashing method and arrested fermentation for the production of low-alcohol and non-alcohol beers was studied. Therefore, five regimes for fermentation of wort with reduced fermentable sugar content with top-fermenting yeast strain at low temperatures and pitching rates were investigated. According to the fermentation dynamic results the decrease in the fermentation temperature from 10 °C to 5 °C at pitching rate of 109 Colony Forming Units cm-3 ( CFU cm-3 ) led to significantly reduced concentrations of ethanol and secondary metabolites in beer. The temperature decrease from 10 °C to 7 °C at pitching rate of 107 CFU cm-3 resulted in a decrease in the alcohol concentration and increase in all the secondary metabolite concentrations except for the vicinal diketones concentration. Data show that yeast biomass does not grow at 5 °C and at inoculum concentration of 107 CFU cm-3, which makes fermentation impossible. Fermentation kinetics using Monod's model supplemented with product inhibition was also investigated. Up to 1.7 % of alcohol accumulates in the beer in some of the variants within 7 days. At low fermentation temperatures, yeast biomass utilizes part of the substrate to maintain its vital activity under stress fermentation conditions, which leads to a reduction in the amount of alcohol synthesized. The synthesis and reduction of the secondary metabolites was delayed compared to conventional beer fermentation. The sensory evaluation of the beers produced showed that the most appealing beer was the one produced at 10 °C and pitching rate of 109 CFU cm-4 [ABSTRACT FROM AUTHOR]

Introduction. The aim of the present work was to substantiate for production of low and non-alcoholic beer by changing the wort composition by replacing part of the malt with unmalted barley. Materials and methods. Industrial malt and non-malted barley were used. The alcohol fermentation was carried out using free and alginatechitosan encapsulated top-fermenting yeast strain Saccharomyces cerevisiae S-33. The mashing regime included two pauses - 30 min at 50 °C and 60 min at 77 °C. The aldehydes were determined according to the bisulfite method, the ester concentration was determined by ester saponification with NaOH. Metabolites were determined after simple sample distillation of the beer. Results and discussion. The wort extract decreased with the increase in the quantity of non-malted barley. In the selected mashing process, the fermentable sugars varied from 3.4 to 4.17% and accounted for about 50% of the laboratory wort extract. Use of 20% barley as adjunct led to a decrease in wort extract by 10% but it did not significantly affect viscosity. A major drawback of the use of non-malted barley is the increase in the laboratory wort filtration time. Filtration time was within 60-75 minutes when the adjunct was up to 20%. It was selected to replace 20% of the malt with unmalted barley. Wort in semi-industrial conditions with the thus selected quantitative malt/barley ratio was produced (8.03% (w/w) extract and fermentable sugar content of 3.7%.). The resulting wort was subjected to alcoholic fermentation at 10 °C for 7 days with free and immobilized cells, and for each variant the fermentation kinetics were determined. The process with free cells was relatively slow and in the first 2-3 days up to 0.4% of alcohol was accumulated, which corresponds to a fermentation rate of 11%. Changes occurred in secondary metabolism - increased ester production, normal higher alcohol formation and weak carbonyl compounds synthesis. In the immobilized cells, the fermentation start was also delayed. The actual process started after the 4th day, the fermentation quickly caught up with the free cell fermentation. As a result, more alcohol (about 0.7% w/w) was accumulated in the laboratory beer, thus enabling its classification as low-alcohol beer, and, fewer metabolites accumulated in the beer, which, in combination with the low fermentation temperature, had a negative effect on the taste profile. Conclusions. Technological regimes for production of low alcohol and non-alcoholic beer have been selected on the basis of analysis of wort sugars, as well as on a study of fermentation kinetics at low temperatures with free and immobilized yeast cells. [ABSTRACT FROM AUTHOR]

Three different kinetic models - Monod's model, Monod's model with substrate inhibition, and Monod's model with substrate and product inhibition were developed for studying of beer fermentation with free and immobilized cells at different main fermentation and maturation temperatures. The most accurate model was Monod's model with substrate and product inhibition. It showed that maturation temperature had no effect on primary metabolism but it affected significantly the secondary metabolites production. In regard to carbonyl compounds and esters, the increase in maturation temperature led to different trends for free and immobilized cells. Regarding the higher alcohols, the increase in maturation temperature resulted in increase in their yield coefficients for both immobilized and free cells. A sensory evaluation of beers produced with free and immobilized cells were also carried out and the results showed similar results for two beer types. [ABSTRACT FROM AUTHOR]