Several aspects related to cereal fermentations were reviewed in the literature
section of this study. These aspects included among others, the history of
indigenous cereal fermentation, factors that affect cereal fermentation, potential
microbiological hazards of cereal fermentation, recent advances in related
industry, and the future of fermented foods. A wide variety of recipes exists
across the African continent and the beers are known by many local names. In
particular this study focussed on mahewu and umqombothi, both made from a
combination of maize and sorghum, fermented beverages consumed in South
Africa. Improved process technologies such as the use of starter cultures can
lead to improved product characteristics and consequently better health
attributes for the consumer of these indigenously fermented products.
During the fermentation processes for umqombothi and mahewu, yeasts, lactic
acid bacteria, moulds and enterobacteriaceae were present at the start of the
process but as fermentation progressed yeasts and lactic acid bacteria were the
dominant microorganisms. This was over a 48 h, and 3 day, fermentation period
for the umqombothi and mahewu respectively. Home-, township-, and laboratorymade
samples of umqobothi were compared while for mahewu, the comparison
was between the home- and laboratory-made samples. Results from different
production sites were not significantly different although there were instances
that called for improved hygiene as contaminants were found in some samples.
Yeasts isolated from umqombothi were identified and these included; Candida
ethanolica, C. haemuloni, C. sorbophila, Dekkera anomala, Dekkera bruxellensis,
Saccharomycopsis capsularis and Saccharomyces cerevisiae. The yeasts
isolated from mahewu were identified and the predominant strains were Candida
haemuloni, Candida sorbophila, Debaryomyces hansenii, Saccharomyces
capsularis and Saccharomyces cerevisiae. Confirmation of the yeast identity was
done using sequence analysis of the D1/D2 domain using primer pairs
NL-1(5â-GCATATCAATAAGCGGAGGAAAAG) and NL-4(5â-
GGTCCGTGTTTCAAGACGG). Scanning electron microscopy was performed on the interior surface of a pot
used for indigenous cereal fermentation. The images obtained confirmed the
presence of biofilm on the surface and the microorganisms present in this biofilm
were predominantly yeasts and bacteria. The observed proximity of yeasts to the
bacterial cells lent further support to the suggestion of a symbiotic relationship
existing between these microorganisms in indigenous cereal fermentations.
Biofilms are not homogenous in composition but are complex matrices composed
of microcolonies interspersed with channels allowing the movement of fluids and
nutrients. It therefore follows that a combination of different techniques that are
available may be required to give the most accurate picture of the true biofilm
structure and organisation.
Indigenous cereal fermented products are an integral part of the diet of many
African households. Several advantages do arise from the fermentation of
cereals and improvement of this process will not only lead to better health
attributes but also the production of fermented beverages with guaranteed and
consistent quality. This augurs well for the producers of fermented products as
more consumers become aware of the health properties of fermented products
and this trend is only likely to improve in the future.
| Identifer | oai:union.ndltd.org:netd.ac.za/oai:union.ndltd.org:ufs/oai:etd.uovs.ac.za:etd-10302009-091411 |
| Date | 30 October 2009 |
| Creators | Katongole, Joseph Nicholas |
| Contributors | Prof BC Viljoen |
| Publisher | University of the Free State |
| Source Sets | South African National ETD Portal |
| Language | en-uk |
| Detected Language | English |
| Type | text |
| Format | application/pdf |
| Source | http://etd.uovs.ac.za//theses/available/etd-10302009-091411/restricted/ |
| Rights | unrestricted, I hereby certify that, if appropriate, I have obtained and attached hereto a written permission statement from the owner(s) of each third party copyrighted matter to be included in my thesis, dissertation, or project report, allowing distribution as specified below. I certify that the version I submitted is the same as that approved by my advisory committee. I hereby grant to University Free State or its agents the non-exclusive license to archive and make accessible, under the conditions specified below, my thesis, dissertation, or project report in whole or in part in all forms of media, now or hereafter known. I retain all other ownership rights to the copyright of the thesis, dissertation or project report. I also retain the right to use in future works (such as articles or books) all or part of this thesis, dissertation, or project report. |
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