Food safety and the occurrence of diarrhoea are a challenge in the management of food
systems in Africa. Infections arising from diarrhoea can be very devastating on the
population, especially children. The traditional fermented maize dough systems have
been identified as being able to reduce considerably the growth of diarrhoeal causing
organisms and improve safety
The study was set up to investigate: 1. The survival of selected diarrhoeal causing
bacteria (Salmonella, Shigella and Escherichia coli) in maize dough fermenting systems
(steeping water, maize dough, Ga kenkey water and maize dough porridge koko) to
determine the safety of the products; 2. The survival of four Escherichia coli strains in
synthetic medium containing lactic and acetic acids; 3. Tolerance of the dominant
yeasts (Candida krusei and Saccharomyces cerevisiae) involved in maize fermentation
for lactic acid. 4. Changes in short-term intracellular pH of single cells of Candida
krusei and Saccharomyces cerevisiae in the presence of high and low concentrations of
lactic acid to explain their tolerance for lactic acid.
Five Salmonella species, three Shigella species, five pathogenic Escherichia coli strains
and two non-pathogenic strains were inoculated into fermented maize dough systems at
a concentration of 106 - 107 cfu/ml at 28 °C. Viable cells were recovered on selective
and non-selective media. Almost all the bacteria survived in maize steeping water for
48 h without reduction in numbers. All the salmonellae and shigellae and two E. coli
strains were completely inhibited in fermenting maize dough after 48 hours whilst three
E. coli strains (026 (VTEC), 0157 (VTEC II) and 03 EAggEC) survived for 48 h but were significantly reduced by more than 3 log units. None of the Salmonella strains
survived in koko for 24 h but Sh. flexneri 2a II and four pathogenic E. coli strains
(0157 (VTEC II), 026 (VTEC), 03 (EAggEC), 0111 (EPEC)) and one laboratory
strain E. coli K12, survived in koko for 48 h with less than 2 log reductions. All the
bacteria were completely inhibited in kenkey water after 24 h. The decrease in
populations of the bacteria in the different fermentation systems was observed at pH of
Greater numbers of survivors were recovered with non-selective medium than with a
selective medium for Gram-negative bacteria.
In Trypticase Soy Broth Yeast Extract (TSBYE) supplemented with lactic and acetic
acids in concentrations found in fermented maize dough systems, E. coli strains 0111
(EPEC), 03 (EAggEC), K12 and M23 were inhibited to various extents.
Concentrations of 31 - 62 mM, undissociated lactic acid had only a bacteriostatic effect
on the four pathogens, while above 62 mM, a bactericidal effect was noted after 24 h.
Concentrations of > 17 - 33 mM undissociated acetic acid were required to completely
inhibit the four E. coli strains. These results confirm that fermented maize dough
systems have antimicrobial properties which may inhibit the survival of some
pathogenic and non-pathogenic bacteria. The extent of inhibition varied among the
species investigated, namely Salmonella, Shigella and Escherichia coli; and also among
the maize dough systems. The presence of lactic acid at low pH was found to be the
main anti-microbial property of the fermented maize dough systems.
CDR, C (2021). Microbial Growth Responses In Fermented Maize Dough Systems. Afribary.com: Retrieved April 10, 2021, from https://afribary.com/works/microbial-growth-responses-in-fermented-maize-dough-systems
Coalition, CDR. "Microbial Growth Responses In Fermented Maize Dough Systems" Afribary.com. Afribary.com, 06 Apr. 2021, https://afribary.com/works/microbial-growth-responses-in-fermented-maize-dough-systems . Accessed 10 Apr. 2021.
Coalition, CDR. "Microbial Growth Responses In Fermented Maize Dough Systems". Afribary.com, Afribary.com, 06 Apr. 2021. Web. 10 Apr. 2021. < https://afribary.com/works/microbial-growth-responses-in-fermented-maize-dough-systems >.
Coalition, CDR. "Microbial Growth Responses In Fermented Maize Dough Systems" Afribary.com (2021). Accessed April 10, 2021. https://afribary.com/works/microbial-growth-responses-in-fermented-maize-dough-systems