Effect of heat treatment on brewer's yeast fermentation activity (original) (raw)
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Effects of fermentation temperature on the strain population of Saccharomyces cerevisiae
International Journal of Food Microbiology, 2003
The influence of fermentation temperature (from 15 to 35 jC) on a mixed strain population was studied. Mitochondrial DNA analysis was used to differentiate Saccharomyces cerevisiae strains and the frequency of each strain during the alcoholic fermentation was determined. The chemical analyses of resulting wines were carried out. The temperature determined how Saccharomyces strains developed and how effectively they fermented. Some strains performed better at high temperatures and others at low temperatures. The maximal population size was similar at all temperatures. At low temperatures, however, it was reached later though it remained constant throughout the alcoholic fermentation. On the other hand, viable cells decreased at high temperatures, especially at 35 jC. Obviously, the composition of the wines changed as the temperature of fermentation changed. At low temperatures, alcohol yield was higher. Secondary metabolites to alcoholic fermentation increased as the temperature increased. Glycerol levels were directly affected by temperature. D
EFFECT of DRYING TYPE and DRYING CONDITIONS OVER FERMENTATIVE ABILITY of BREWER'S YEAST
Journal of Food Process Engineering, 2003
In this work the growth and glucose consumption as well as alcohol production kinetics offresh and rehydrated brewer's yeast were evaluated. Dried yeast was obtained by fluidized bed and spray drying. Based on fermentation trials, there was no difference between the number of viable cells determined at the end of the stationary phase, however diflerences in growth velocity between the dehydrated yeast and the fresh yeast cream were found. Regarding alcohol production, no differences were found in most of the treatments (F2. F3, F4*, A I , A2, A3 and A4) with respect to the fresh yeast. The brewery dried yeast with an efticient viability and fennentative ability can be stored at least 4 months and used when required. Therefore the need of conventional propagation and fresh yeast transport may be eliminated. ' Author to whom all correspondence shall be addressed. Dra. Guadalupe Rodriguez Jimenes. M.A. de Quevedo 2779, Col. Formando Hogar. Veracruz. Ver., C.P. 91850. Mexico. TEL: (52) 29 34 14 69; FAX: (52) 29 34 57 01; EMAIL lupitaj@itver.edu.mx Journal of Food Process Engineering 26 (2003) 135-147. All Righrs Reserved. '
High temperature fermentations and thermotolerant yeast species in the brewing scene
2020
In this thesis the effects of high temperatures on fermentation characteristics, as well as the use of thermotolerant yeasts in brewing are investigated. Specifically, the effects of high temperatures on yeast growth and fermentation rate are examined and the characteristics of the products produced at high temperature fermentations are analyzed. Signal transduction pathways involving reactive oxygen species as second messengers seem to participate in the decrease of yeast growth rate at supraoptimal temperatures, while ethanol, lactic acid and acetic acid are described as 'escape valves' for the yeast cells. Oxidative stress is linked to thermal stress. Furthermore, the effects of high fermentation temperatures on the production of volatile compounds during fermentation are overviewed. Esters' and higher alcohols' levels increase with the temperature and the promoted expression of specific genes which are involved in their production is the reason for that. Furtherm...
International Journal of Food Microbiology, 1993
A comparative analysis of the initial and final population of yeasts, lactic acid bacteria and psychrotrophic I~acteria. in a number of chilled fisv, Js, varying in ingredients, physico-chcmical characters :rod origin, gave evidence th:tt yeasts could play a significant role in the spoilage. The yeast lmlpulations appeared to be unexpectedly unifi~rm and comprised principally strains of Yarrowia lil~dytica. IX'b(~'mnyces han.~enii and I'ichha mcmbrmua'fuch'n,~. A survey of 02 isolates, comprising physiological characteristics such as growth temperatures, proteolytic and lipolytic activities, hydrophobicity, a,, and preservative tolerance, it) addition to organic acid production, indicated that these dominant species have very few common characters and that they arc endowed with a spoilage potential probably linked to different physiological properties. The isolates of Y./il~dyth'a cxibited the strongest proteolytic and lipolytic activities and a pronounced hydrophohicity while D. hansemi isolates were characterized by a high growth rate at low tempcratt, re and at intermediate a,,. P. memhmnac.f(wicn.~ isolates showed a remarkable tolerano: to acetic acid as a sole selective factor. A hyp~thcsis of separate growth h~:i, in multicoml~ment or I~)lyphasic fired sy~tcnts, was tbrnmlated.
THERMAL RESISTANCE OF WILD YEAST AND SACCHAROMYCES CARLSBERGENSIS IN "PEJA" PILSEN BEER
This study was performed to determine the thermal resistance of wild yeast and Saccharomyces carlsbergensis in Peja Pilsen beer (pH = 4.5 ± 0.2 and percentage of alcohol by volume = 4.7 ± 0.25 %). This investigation included determining Decimal reduction times (D-values) and Z-values. The corresponding D 48°C , D 50°C D 52°C and D 54°C values calculated from survivor plots for wild yeast were 4.60, 2.20, 0.515 and 0.348 minutes, respectively. D-values for Saccharomyces carlsbergensis at 47 o , 48 o , 49 o , 50 o , 51 o and 52 ºC were 3.86, 2.41, 1.43, 0.82, 0.59 and 0.32 minutes, respectively. The Z-value for wild yeast was 5.01 o C and for Saccharomyces carlsbergensis was 4.68 o C. These findings indicate that Saccharomyces carlsbergensis has greater temperature dependence than wild yeast. Relevant data, in the form of D and Z-values calculated in the various temperatures, potentially useful for the establishment of regimes of thermal control of wild/Saccharomyces carlsbergensis yeasts.
European Food Research and Technology, 2011
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2017
This paper describes the use of the dry lager brewing Saccharomyces cerevisiae (Saflager S-189) yeast strain in a beer factory from the moment of inoculation until the secondary fermentation stage. The research follows the physico-chemical and microbiological parameters of the inoculum, primary fermentation, secondary fermentation and unfiltered beer. Special attention was paid to the way the yeast was prepared for inoculation. In the laboratory measurements made on wort and beer during the fermentation process, different devices existing in the laboratory factory from S.C. Bermas S.A. Suceava were used, such as: saccharimeters, thermometers, oxygen content, microscop, Thoma camera, carbon dioxide, refractometer for beer analysis, viscosimeter, spectrophotometer e.g. The yeast presents good flocculation ability, a quick adaptation to the medium conditions (wort composition) and the beer obtained with this strain yeast presents good physical-chemical parameters and organoleptic ones.
Influence of dough freezing on Saccharomyces cerevisiae metabolism
Zbornik Matice srpske za prirodne nauke, 2007
The need to freeze dough is increasing in bakery production. Frozen dough can be stored for a long time without quality change. The capacity of bakery production can be increased in this way, and in the same time, the night shifts can be decreased. Yeast cells can be damaged by freezing process, resulting in poor technological quality of dough after defrostation (longer fermentation of dough). The influence of frozen storage time of dough on survival percentage of Saccharomyces cerevisiae was investigated. Dough samples were taken after 1, 7, 14 and 28 days of frozen storage at-20°C. After defrosting, at room temperature, samples were taken from the surface and the middle part of dough (under aseptic conditions), and the percentage of living S. cerevisiae cells was determined. During frozen storage of dough, the number of living S. cerevisiae decreased. After 28 days of frozen storage, the percentage of live cells on the surface and inside the dough was 53,1% and 54,95%, respectively. The addition of k-carragenan to dough increased the percentage of living cells in the middle part of dough up to 64,63%. Pure cultures, isolated from survived S. cerevisia cells in frozen dough by agar plates method (Koch's method), were multiplied in optimal liquid medium for yeasts. The content of cytochromes in S. cerevisiae cells was determined by spectrophotometric method. The obtained results showed that the content of cytochromes in survived S. cerevisiae cells was not affected by dough freezing process. Growth rate and fermentative activity (Einchor's method) were determined in multiplied cells.
Impact of temperature on beer fermentation kinetics
2018
Microbial processes are highly dependent on temperature. This paper aims to study the influence of temperature on fermentation process on experimental and industrial scale. We were focused to determine the preexponential coefficients and the activation energy for experimental and industrial conditions and to quantify the amount of heat to be removed from fermenter to keep it under constant temperature during fermentation process. Substrate used for fermentation was beer industrial wort 12 Balling and yeast strain used was bottom fermentation yeast "Saccharomyces Carlsbegensis SP 35". Evaluation and comparison of kinetic parameters in different fermentation conditions were carried out. Temperatures used for different batches in industrial trials were 5, 20, 25 and 35 ° C and 8, 12 and 16 °C for experimental trials. Kinetic models developed were able to predict with a relatively high accuracy the experimental results achieved under non-thermal conditions and can be used to s...