African Sorghum Beer Research Articles

Analysis of the bacterial and fungal populations in South African sorghum beer (umqombothi) using full-length 16S rRNA amplicon sequencing

There is a need to profile microorganisms which exist pre-and-post-production of umqombothi, to understand its microbial diversity and the interactions which subsequently influence the final product. Thus, this study sought to determine the relative microbial abundance in umqombothi and predict the functional pathways of bacterial and fungal microbiota present. Full-length bacterial 16S rRNA and internal transcribed spacer (ITS) gene sequencing using PacBio single-molecule, real-time (SMRT) technology was used to assess the microbial compositions. PICRUSt2 was adopted to infer microbial functional differences. A mixture of harmful and beneficial microorganisms was observed in all samples. The microbial diversity differed significantly between the mixed raw ingredients (MRI), customary beer brew (CB), and optimised beer brew (OPB). The highest bacterial species diversity was observed in the MRI, while the highest fungal species diversity was observed in the OPB. The dominant bacterial species in the MRI, CB, and OPB were Kosakonia cowanii, Apilactobacillus pseudoficulneus, and Vibrio alginolyticus, respectively, while the dominant fungal species was Apiotrichum laibachii. The predicted functional annotations revealed significant (p < 0.05) differences in the microbial pathways of the fermented and unfermented samples. The most abundant pathways in the MRI were the branched-chain amino acid biosynthesis super pathway and the pentose phosphate pathway. The CB sample was characterised by folate (vitamin B9) transformations III, and mixed acid fermentation. Biotin (vitamin B7) biosynthesis I and l-valine biosynthesis characterised the OPB sample. These findings can assist in identifying potential starter cultures for the commercial production of umqombothi. Specifically, A. pseudoficulneus can be used for controlled fermentation during the production of umqombothi. Likewise, the use of A. laibachii can allow for better control over the fermentation kinetics such as carbohydrate conversion and end-product characteristics, especially esters and aroma compounds.

Imperial Hops: Beer in the Age of Empire

ABSTRACT The global spread of lager beers such as Heineken, Budweiser, Sapporo and Corona offers a seemingly classic case of cultural imperialism displacing local beverages including Japanese sake, Bolivian chicha, and African sorghum beer. Empire indeed launched beer to global status, beginning with British brewers shipping ale and porter to provision imperial agents around the world, although by the turn of the twentieth century, the crisp, clean taste of German lager had largely displaced heavier British brews from colonial markets. Lager beer also came to be seen as a civilizing taste in comparison with strongly flavored indigenous drinks, attracting many local consumers, despite imperial prohibitions against native consumption of European alcohol. Ultimately, Europe’s export brewers lost out to migrant brewers, who transplanted barley and hops, installed refrigerated machinery, and freed settler colonists and Native consumers alike from their reliance on beer from the metropolis, thereby demonstrating the limits of empire.

Sustainable Production of African Traditional Beers With Focus on Dolo, a West African Sorghum-Based Alcoholic Beverage

Spontaneously fermented sorghum beers remain by far the most popular traditional cereal-based alcoholic beverages in Africa. Known under various common names (traditional beers, sorghum beers, opaque, native or indigenous beers) they are also recognized under various local names depending on the region or ethnic group. Dolo and pito are two similar traditional beers popular in West African countries including Burkina Faso, Mali, Ghana, Benin, Togo, Nigeria and Ivory Coast. These low-alcoholic beers are nutritious and contribute to the nutritional balance of local populations, as well as to their socio-cultural and economic well-being. The production of African traditional beers remains one of the major economic activities, creating employment and generating substantial income that contributes to livelihoods as well as the countries' economic systems. Their processing (malting and brewing) is still artisanal, based on traditional family know-how. The brewing process involves either an acidification and an alcoholic fermentation phases, or a mixed fermentation combining LAB and yeasts. Saccharomyces cerevisiae has been identified as the dominant yeast species involved in the alcoholic fermentation, with a biodiversity at strain level. LAB involved in the processing belong to the genera of Limosilactobacillus, Lactobacillus, Pediococcus, Leuconostoc, Lactococcus, Streptococcus, and Enterococcus. Molds (Aspergillus, Penicillium, Rhizopus, Geotrichum), and acetic bacteria are often associated with the malting and brewing processes. Challenges for sustainable production of African sorghum beer include inconsistent supply of raw materials, variability in product quality and safety, high energy consumption and its impact on the environment, poor packaging and short shelf-life. For sustainable and environmentally-friendly production of African sorghum beers, there is the need to assess the processing methods and address sustainability challenges. Strategies should promote wider distribution and adoption of improved sorghum varieties among farmers, prevent losses through the adoption of good storage practices of raw material, promote the adoption of improved cook stoves by the brewers, develop and adopt starter cultures for controlled fermentation, regulate the production through the establishment of quality standards and better valorize by-products and wastes to increase the competitiveness of the value chain. Appropriate packaging and stabilization processes should be developed to extend the shelf-life and diversify the channels for sustainable distribution of African cereal-based alcoholic beverages.

West African sorghum beer fermented with Lactobacillus delbrueckii and Saccharomyces cerevisiae: shelf-life and consumer acceptance

West African sorghum beer fermented with <i>Lactobacillus delbrueckii</i> and <i>Saccharomyces cerevisiae:</i> shelf-life and consumer acceptance

Phenotypical and molecular characterization of yeast content in the starter of “Tchoukoutou,” a Beninese African sorghum beer

Tchoukoutou is a Beninese African sorghum beer obtained by mixed fermentation including different yeast and lactic acid bacteria (LAB). Until now, the make-up of the starter’s whole microbial communities and the main reason for the diversity of this special beer’s organoleptic quality (taste and flavor) have remained unknown. A total of 240 yeasts isolated from a Tchoukoutou starter have been characterized following the polyphasic approach and using yeast phenotype (morphology and physiology), proteins (MALDI-TOF MS), ITS1-5.8S-ITS4 and D1/D2 of the large subunit (LSU) rRNA gene as biomarkers. The microbial ecology of the starter used to produce Tchoukoutou is diverse and belongs to different strains of four species including Saccharomyces cerevisiae (75.17 %) as the dominant yeast, followed by Pichia kudriavzevii (17.24 %), Candida ethanolica (4.14 %) and Debaryomyces hansenii complex (3.45 %). D. hansenii complex and C. ethanolica are two yeast species which have never yet been isolated from Tchoukoutou. Some S. cerevisiae with an interesting fermentative profile are able to metabolize lactic acid (lactic acid bacteria metabolite) and therefore may increase the beer pH, thereby allowing the growth of LAB for further beer maturation and flavor enhancement during Yeast-LAB mixed fermentation. The co-presence of the non-Saccharomyces with S. cerevisiae in sorghum beer starter depends for the agroecology zones.

Production of freeze-dried yeast culture for the brewing of traditional sorghum beer, tchapalo.

Freeze-drying is a well-known dehydration method widely used to preserve microorganisms. In order to produce freeze-dried yeast starter culture for the brewing purpose of African sorghum beer, we tested protective agents (sucrose, glucose, glycerol) in combination with support materials (millet, maize, sorghum, and cassava flours) at 1:1 ratio (v/v). The yeast strains Saccharomyces cerevisiae F 12-7 and Candida tropicalis C 0-7 previously isolated from sorghum beer were used in a mixed culture at a ratio of 2:1 (C.tropicalis/S.cerevisiae). After the freeze-drying, the residual water contents were between 0.78 -2.27%, 0.55 -4.09%, and 0.40-2.61%, respectively, with sucrose, glucose and glycerol. The dried yeasts viabilities were between 4.0% and 10.6%. Among the protective agents used, sucrose was found to be the best protectant giving cell viabilities of 8.4-10.6%. Considering the support materials, millet flour was the best support after drying. When the freeze-dried yeast powders were stored at 4°C and room temperature (25-28°C) for up to 3months, the survival rates were the highest with cassava flour as the support material.

Impact of brewing process operations on phytate, phenolic compounds and in vitro solubility of iron and zinc in opaque sorghum beer

Opaque sorghum beer is a significant component of the diet of millions of poor people in rural Africa. This study reports the effect of traditional brewing operations on its level of micronutrients, especially iron and zinc. The example of a West African sorghum beer, tchoukoutou, in Northern Benin was studied. The beer was characterized and the impact of process unit operations on phytate, phenolic compounds, and Zn and Fe in vitro solubility was evaluated. The major microorganisms involved in the beer fermentation were Saccharomyces cerevisiae and heterofermentative lactobacilli. The manufacturing process reduces the phytate content by nearly 95%, particularly during germination, mashing-boiling and fermentation. The level of reactive phenolic groups increased as a result of germination and fermentation as well as from a shift in dry matter composition. Simultaneously with these modifications, an increase of Fe solubility was observed, and a correlation between phytate and Fe solubility ( R 2 = 0.85 ) was established. No clear correlation could be established between the Zn solubility and the phytate content of the products. During beer manufacturing, significant losses of minerals occur particularly during soaking and mashing/filtration; thus the quantity of minerals available to consumers is restricted. Improvements aiming to minimize such losses are highly desirable.

In vitro screening of probiotic properties of Saccharomyces cerevisiae var. boulardii and food-borne Saccharomyces cerevisiae strains

The probiotic potential of 18 Saccharomyces cerevisiae strains used for production of foods or beverages or isolated from such, and eight strains of Saccharomyces cerevisiae var. boulardii, was investigated. All strains included were able to withstand pH 2.5 and 0.3% Oxgall. Adhesion to the nontumorigenic porcine jejunal epithelial cell line (IPEC-J2) was investigated by incorporation of 3H-methionine into the yeast cells and use of liquid scintillation counting. Only few of the food-borne S. cerevisiae strains exhibited noteworthy adhesiveness with the strongest levels of adhesion (13.6–16.8%) recorded for two isolates from blue veined cheeses. Merely 25% of the S. cerevisiae var. boulardii strains displayed good adhesive properties (16.2–28.0%). The expression of the proinflammatory cytokine IL-1α decreased strikingly in IPEC-J2 cells exposed to a Shiga-like toxin 2e producing Escherichia coli strain when the cells were pre- and coincubated with S. cerevisiae var. boulardii even though this yeast strain was low adhesive (5.4%), suggesting that adhesion is not a mandatory prerequisite for such a probiotic effect. A strain of S. cerevisiae isolated from West African sorghum beer exerted similar effects hence indicating that food-borne strains of S. cerevisiae may possess probiotic properties in spite of low adhesiveness.

Identification and characterization of Saccharomyces cerevisiae strains isolated from West African sorghum beer

Identification and characterization of Saccharomyces cerevisiae strains isolated from West African sorghum beer

Identification and characterization of Saccharomyces cerevisiae strains isolated from West African sorghum beer.

The occurrence and characterization of yeasts isolated from sorghum beer produced in Ghana and Burkina Faso, West Africa, were investigated. The yeasts involved in the fermentations were found to consist of Saccharomyces spp. almost exclusively. Of the isolates investigated, 45% were identified as Saccharomyces cerevisiae, whereas more than half of the isolates (53%) had physiological properties atypical of S. cerevisiae or any other member of the complex sensu strictu, as they were able to assimilate only glucose, maltose and ethanol as carbon sources. Both ITS-PCR RFLP and PFGE strongly indicated that these isolates were related to S. cerevisiae, regardless of their phenotypic characteristics. Sequencing of the D1/D2 domain of the 26S rDNA confirmed the close relatedness to S. cerevisiae with 0.5% nucleotide differences. The MAL1 and MAL3 loci were found for all isolates as the only recognized MAL loci. Besides, for 40% of the isolates the MAL61 probe hybridized to a position of about 950 kbp, which has not formerly been described as a MAL locus. The results showed that the spontaneous fermentation of West African sorghum beer is dominated by a variety of strains of S.cerevisiae not previously described, among which starter cultures should be selected.

Microbial populations associated with commercially produced South African sorghum beer as determined by conventional and Petrifilm™ plating

Microbial populations of 46 commercially produced sorghum beer samples from retail outlets in Johannesburg, South Africa, were enumerated and characterized. Aerobic plate counts, lactic acid bacteria counts and yeast counts were performed by conventional and Petrifilm™ plating. Conventional methods yielded yeast counts of 7.84 log CFU/ml, lactic acid bacteria counts of 6.44 log CFU/ml and aerobic plate counts of 5.96 log CFU/ml. In comparison, Petrifilm™ counts were 7.85 log CFU/ml for yeasts, 5.31 log CFU/ml for lactic acid bacteria and 5.34 log CFU/ml for aerobic bacteria. Characterization of 419 predominant bacterial isolates from Standard One Nutrient Agar, MRS Agar and corresponding Petrifilm™ plates yielded 88.0% lactic acid bacteria, 8.4% Bacillus species, 2.9% Micrococcus species and 0.7% Gram negative bacteria. Composition of predominant lactic acid bacteria populations from Standard One Nutrient Agar and both types of Petrifilm™ plates showed marginal differences. Increased proportions of heterofermentative lactic acid bacteria were, however, isolated from conventional MRS Agar compared to the modified Petrifilm™ product which represented the equivalent to MRS Agar.

A SURVEY OF AFLATOXINS IN INDUSTRIALLY BREWED SOUTH AFRICAN SORGHUM BEER AND BEER STRAININGS

The results of a five year survey of the aflatoxin levels found in industrially brewed South African sorghum beer and its spent grains (known as beer strainings in the trade) are presented. Methods of analysis of these commodities are given. It is suggested that aflatoxins in beer may be more conveniently monitored, indirectly, by determining levels present in the beer strainings. Data on aflatoxin levels found in raw materials used in the sorghum beer industry are given. Although some sorghum malt samples were rich in aflatoxins no samples of sorghum beer contained significant amounts of aflatoxins.