Effect of mashing with commercial enzymeson the properties of sorghum worts

Comparative mashing trials of sorghum showed that the enzyme complex used to convert raw sorghum in brewing produced different levels of protein breakdown but reduced foaming potentials to similar degrees. Significant improvement in foaming potentials of worts were achieved when usual mashing procedures were replaced by a two-stage mashing process where late addition of gelatinized sorghum grist re-established foam stability. This late addition of part of the gelatinized grist may limit enzymic destruction of foam-stabilizing substances.     

Effect of mashing with commercial enzymeson the properties of sorghum worts

Comparative mashing trials of sorghum showed that the enzyme complex used to convert raw sorghum in brewing produced different levels of protein breakdown but reduced foaming potentials to similar degrees. Significant improvement in foaming potentials of worts were achieved when usual mashing procedures were replaced by a two-stage mashing process where late addition of gelatinized sorghum grist re-established foam stability. This late addition of part of the gelatinized grist may limit enzymic destruction of foam-stabilizing substances.     

Sorghum: a cereal with lager beer brewing potential

The potential of sorghum as an alternative substrate for lager beer brewing was recognized over five decades ago. Factors which appear to influence brewing with sorghum include: the variety of sorghum, storage time, steep period, germination time, duration and levels of temperature-time sequence of the kilning cycle and temperature-time regimes during mashing. Malts from sorghum varieties that have high diastatic power, amylase and starch contents are desirable. Soluble and insoluble amylases in grain sorghum contribute towards the hydrolysis of grain constituents during mashing. Optimizing conditions for malting, mashing and fermentation are therefore necessary for the production of acceptable sorghum lager beer. This review aims to update research results on lager beer brewing with sorghum.     

Developments in the malting and brewing trials with sorghum

A comparative study of sorghum and barley grains reveals structural and physiological differences in their aleurone, embryo and starchy endosperm cells. These differences are responsible for the observed differences in their malting characteristics. Reports on brewing trials with sorghum favour its use as an adjunct to barley malt. Nevertheless, a recent successful resolution of the incompatibility of the gelatinization and saccharification temperatures of sorghum starch through the adoption of a new mashing technique has greatly improved its extract yield. A similar report on the discovery of a Nigerian-grown sorghum variety with improved β-amylase activity as well as high diastatic power will obviously ensure better fermentable extracts. Further research on the development and trial of new sorghum varieties is strongly recommended. The purpose of this review, however, is to highlight research efforts aimed at alleviating the problems of sorghum as a brewing material.     

The use of chitooligosaccharide in beer brewing for protection against beer-spoilage bacteria and its influence on beer performance

Objectives

To identify a biological preservative that can protect beer from microbial contamination, which often results in the production of turbidity and off-flavor.

Results

The antimicrobial activity of a chitooligosaccharide against beer-spoilage bacteria and its effect on the fermentation performance of brewer’s yeast was studied. Chitooligosaccharide with an average 2 kDa molecular weight was the best at inhibiting all tested beer-spoilage bacteria. The application of chitooligosaccharide in the brewing process did not influence the fermentation of brewer’s yeast. The change in beer performance induced by the contamination of Lactobacillus brevis could be effectively controlled by application of chitooligosaccharide in the beer brewing process.

Conclusion

The experimental data suggested that chitooligosaccharide should be an excellent preservative to inhibit beer-spoilage bacteria in the brewing process and in the end product.

     

Use of unmalted sorghum as a brewing adjunct

Hydrolysis of three varieties of unmalted sorghum by endogenous amylases produced sufficient maltose and glucose for subsequent brewing of beer. The optimal temperature and pH of the sorghum amylase activities varied between the three varleties. -Amylase was optimal when used at 60°C and pH 5 for two varieties but at 60°C and pH 6 for another. The optimal -amylase activity was between about 72°C and 75°C for all the sorghum varieties. The activities of the amylases differed considerably between the species.

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Résumé L'hydrolyse de trois variétés de sorghum non maltés par des amylases endogènes produit suffisamment de maltose et de glucose pour la fermentation ultérieure du moût. Les températures et pH optimum des activités amylolytiques du sorghum varient selon la variété. Pour deux variétés, l'activité -amylolytique est optimal lors de son utillsation à 60°C et à pH 5, tandis qu'elle est optimale à 60°C et à pH 6 pour la troistème. L'activité -amylolytique est optimal à environ 72 à 75°C pour toutes les variétés de sorghum. Les activités amylolytiques varient considérablement selon les espèces.

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This work was carried out at the Department of Microbiology, University of Nigeria, Nsukka, Nigeria.     

Mathematical modeling for prediction of endo-xylanase activity and arabinoxylans concentration during mashing of barley malts for brewing

A mathematical model describing the degradation of arabinoxylans by endo-xylanase during mashing process was developed. Endo-xylanase activities and arabinoxylans concentrations in laboratory scale mashing process at different temperature profiles were measured and then used for identifying the model parameters for Harrington barley malt. The modeling errors range for the final concentration of arabinoxylans in wort was -4% to +11.9%. The model developed was also used for predicting the other three different malts mashing processes in laboratory scale, and the prediction errors ranged from -9.5% to +13.6%. The model prediction accuracy for industrial scale mashing process was lower than that in laboratory scale. The simulation results showed that, a lower concentration of arabinoxylans could be achieved when maintaining the mashing-in at 45 degrees C and prolonging the mashing-in time.     

Selective antimicrobial activity of chitosan on beer spoilage bacteria and brewing yeasts

Chitosan (0.1 g l(-1)), assayed in a simple medium, reduced the viability of four lactic acid bacteria isolated during the beer production process by 5 logarithmic cycles, whereas activity against seven commercial brewing yeasts required up to 1 g chitosan l(-1). Antimicrobial activity was inversely affected by the pH of the assay medium. In brewery wort, chitosan (0.1 g l(-1)) selectively inhibited bacterial growth without altering yeast viability or fermenting performance.     

The yeast Saccharomyces cerevisiae- the main character in beer brewing

Historically, mankind and yeast developed a relationship that led to the discovery of fermented beverages. Numerous inventions have led to improved technologies and capabilities to optimize fermentation technology on an industrial scale. The role of brewing yeast in the beer-making process is reviewed and its importance as the main character is highlighted. On considering the various outcomes of functions in a brewery, it has been found that these functions are focused on supporting the supply of yeast requirements for fermentation and ultimately to maintain the integrity of the product. The functions/processes include: nutrient supply to the yeast (raw material supply for brewhouse wort production); utilities (supply of water, heat and cooling); quality assurance practices (hygiene practices, microbiological integrity measures and other specifications); plant automation (vessels, pipes, pumps, valves, sensors, stirrers and centrifuges); filtration and packaging (product preservation until consumption); distribution (consumer supply); and marketing (consumer awareness). Considering this value chain of beer production and the 'bottle neck' during production, the spotlight falls on fermentation, the age-old process where yeast transforms wort into beer.     

Potential use ofGarcinia kola as hop substitute in lager beer brewing

The chemical, brewing and anti-microbial properties of a tropical seed,Garcinia kola, were compared with traditional hops. Treatment ofGarcinia kola with methanolic lead acetate produced a yellow precipitate from which organic acids (alpha acids) were contirmed to be present by thin-layer chromatography. Hops, however, had a higher concentration of organic acids thanGarcinia kola. Laboratory brewing trials withGarcinia kola and hops gave beers with simillar chemical properties. Organoleptically,Garcinia kola beer was as acceptable to tasters as hopped beer except that it had an improved bitterness.Garcinia kola and hop extracts exerted similar anti-microbial effects on two beer spollage micro-organisms (Lactobacillus delbruckii andCandida vini).

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Résumé On a comparé les propriétés chimiques, brassicoles, et antiseptiques d'une graine tropicale,Garcinia kola, à celles des houblons traditionnels. Le traitement deGarcinia kola à l'acétate de plomb en milieu méthanolique a produit un précipité jaune dans lequel on a confirmé la présence d'acides organiques ou acides . Les houblons, toutefois, avaient une concentration plus élevée en acides organiques queGarcinia kola. Des essais de brassage au laboratoire avecGarcinia kola ont produit des bières aux propriétés chimiques sembiables. Sur le plan organolètique, la bière deGarcinia kola a été aussi acceptable pour les goûteurs que la bière de houblon à ceci prés que la première avait une amertume améliorée. Les extraits deGarcinia kola et de houblon ont exercé des effets antimicrobiens semblables sur deux microorganismes contaminant la bière (Lactobacillus delbruckii etCandida vini).

     

Isolation and utilization of indigenous yeast strain for brewing of millet beer (OYOKPO)

Three yeast strains were isolated from a spontaneously fermented native millet (Pennisetum typhoideum) malt beer (Oyokpo). One of the yeast isolates found to have the most highly fermenting capacity was characterised and identified as a strain of Saccharomyces cerevisiae. The yeast was then utilised as the pitching yeast in a subsequent controlled fermentation of millet wort at 20°C for 120 hours. Bitter leaf (Vernonia amagdalina) extract was used as the bittering and flavouring agent. The Oyokpo beer sample produced under these conditions was found to possess both chemical and organoleptic qualities comparable to some extent, to the conventional barley malt beer. At the end of fermentation, the pH, specific gravity, alcohol content, reducing sugar content and protein content of the beer were 4.11, 1.0308, 2.81% (v/v), 4.00 (mg/ml) and 0.84 (mg/ml) respectively.     

Use of high-ethanol-resistant yeast isolates from Nigerian palm wine in lager beer brewing

High-ethanol-resistant yeasts, characterized as Saccharomyces sp., were isolated from Nigerian palm wine with added sucrose for high gravity brewing. The yeast isolates that survived the highest ethanol production were used to ferment brewery wort and produced 8.2 to 8.5% (v/v) ethanol; values almost double that of the control yeast from a local brewery.     

Genetic engineering of brewing yeast to reduce the content of ethanol in beer

The GPD1 gene encoding the glycerol-3-phosphate dehydrogenase was overexpressed in an industrial lager brewing yeast (Saccharomyces cerevisiae ssp. carlsbergensis) to reduce the content of ethanol in beer. The amount of glycerol produced by the GPD1-overexpressing yeast in fermentation experiments simulating brewing conditions was increased 5.6 times and ethanol was decreased by 18% when compared to the wild-type. Overexpression of GPD1 does not affect the consumption of wort sugars. Only minor changes in the concentration of higher alcohols, esters and fatty acids could be observed in beer produced by the GPD1-overexpressing brewing yeast. However, the concentrations of several other by-products, particularly acetoin, diacetyl and acetaldehyde, were considerably increased.     

Growth model and metabolic activity of brewing yeast biofilm on the surface of spent grains: a biocatalyst for continuous beer fermentation

In the continuous systems, such as continuous beer fermentation, immobilized cells are kept inside the bioreactor for long periods of time. Thus an important factor in the design and performance of the immobilized yeast reactor is immobilized cell viability and physiology. Both the decreasing specific glucose consumption rate (q(im)) and intracellular redox potential of the cells immobilized to spent grains during continuous cultivation in bubble-column reactor implied alterations in cell physiology. It was hypothesized that the changes of the physiological state of the immobilized brewing yeast were due to the aging process to which the immobilized yeast are exposed in the continuous reactor. The amount of an actively growing fraction (X(im)act) of the total immobilized biomass (X(im)) was subsequently estimated at approximately X(im)act = 0.12 g(IB) g(C)(-1) (IB = dry immobilized biomass, C = dry carrier). A mathematical model of the immobilized yeast biofilm growth on the surface of spent grain particles based on cell deposition (cell-to-carrier adhesion and cell-to-cell attachment), immobilized cell growth, and immobilized biomass detachment (cell outgrowth, biofilm abrasion) was formulated. The concept of the active fraction of immobilized biomass (X(im)act) and the maximum attainable biomass load (X(im)max) was included into the model. Since the average biofilm thickness was estimated at ca. 10 microm, the limitation of the diffusion of substrates inside the yeast biofilm could be neglected. The model successfully predicted the dynamics of the immobilized cell growth, maximum biomass load, free cell growth, and glucose consumption under constant hydrodynamic conditions in a bubble-column reactor. Good agreement between model simulations and experimental data was achieved.     

The biodiversity of predominant lactic acid bacteria in dolo and pito wort for the production of sorghum beer

AIM: To quantify and identify the predominant lactic acid bacteria (LAB) in dolo and pito wort processing, and to examine their biodiversity at strain level. MATERIALS AND RESULTS: The processing of dolo and pito wort was studied at four production sites in Burkina Faso and Ghana. The succession of dominant micro-organisms, pH and titratable acidity were determined from sorghum malt through mashing and acidification to final wort. In the sorghum malt and during mashing, the LAB counts were 5.7-7.5 log CFU g(-1). Similar levels of yeasts and gram-negative, catalase-positive bacteria were observed. These levels decreased to 3.7-4.5 log CFU g(-1) and相似文献   

Comparisons of methods for introgressing exotic germ plasm into adapted sorghum

The incorporation of exotic germ plasm into breeding populations can broaden and diversify the genetic base of adapted genotypes. To more effectively utilize the genetic resources existing in Sorghum bicolor (L.) Moench, a rapid and efficient method of incorporating exotic genotypes into adapted populations is needed. Therefore, this study was conducted to compare the effectiveness of backcrossing to a broad-based population versus backcrossing to an inbred line for developing improved lines from adapted x exotic crosses. A wild sorghum, a cultivated landrace, and a converted sorghum line were crossed to an inbred line (CK60) and a broad-based population (KP9B). After two generations of backcrossing to the respective adapted parent, 50 F₂ lines were derived from each of the backcross generations of every mating and evaluated at three test environments. Backcrossing to an inbred line (CK60) gave fewer high-yielding segregates and generated less genetic variation than backcrossing to a population (KP9B). Also, the number of agronomically acceptable lines derived from each CK60 mating was fewer than that derived from the corresponding mating with KP9B. Overall, the use of a broad-based population as an adapted recurrent parent for introgressing exotic genotypes may provide good opportunities for developing suitable inbred lines from adapted x exotic backcrosses.Contribution no. 93-499-J from the Kansas Agricultural Experiment Station     

Saccharomyces cerevisiae and Candida tropicalis as starter cultures for the alcoholic fermentation of tchapalo, a traditional sorghum beer

Starter cultures of Candida tropicalis and Saccharomyces cerevisiae isolated from tchapalo were tested in pure culture and co-culture of four ratios [2:1, 25:4, 1:4, 2:3 (cells/cells)] for their ability to ferment sorghum wort to produce tchapalo. All the starters showed means growth rate between 0.043 and 0.101 h^?1. Only C. tropicalis in pure culture showed growth rate lower than that of S. cerevisiae in single culture. During fermentation, according to total soluble solids depletion, yeast starters could be grouped in four different profiles. But in the beer produced, total soluble solids contents were statistically identical. The lowest values were obtained with co-culture C. tropicalis + S. cerevisiae in the ratios of 2:1 and 2:3. Starter cultures with large ratio of C. tropicalis produced a higher organic acids and 2-butanone than S. cerevisiae in pure culture. However, co-culture C. tropicalis + S. cerevisiae (2:1) was the alone starter which produced higher ethanol than S. cerevisiae in pure culture. The beers produced with C. tropicalis + S. cerevisiae (25:4), C. tropicalis + S. cerevisiae (1:4) and C. tropicalis were widely different from those produced with the others starter cultures.     

In vitro culture methods in sorghum with shoot tip as the explant material

Twenty-four diverse genotypes of sorghum were evaluated for response to callus induction and plant regeneration with two media viz., MS and NBKNB using shoot tips as the start material to identify a model genotype. None of the genotypes tested showed promising results. Therefore, alternative methods of in vitro pathways using shoot meristem isolated from shoot tips were explored. Shoot apical meristems were isolated and were induced to multiple shoots or multiple shoot buds pathway by manipulation of thidiazuron (TDZ), 6-benzyl adenine (BAP) and 2, 4-dichlorophenoxy acetic acid (2, 4-D). Choice of the pathway whether large-scale multiplication of shoots or production of target tissues for transformation can be exercised based on the needs and applications. A simple procedure, for large scale handling of shoot tips is described in detail. Electron microscopic studies revealed that meristems isolated from 7-day-old seedlings are superior because of possessing greater number of transformation competent cells.