(khamir) produced from sorghum in Gizan region, Saudi Arabia

224 M.A.A. GASSEM
(Bayadh) increased from 0·32 to 1·2% in 12 h and at the end
of 24 h fermentation, it was 1·60%. Similar results were
obtained for the Hamra variety.
Classification of micro-organisms
Different micro-organisms were isolated at different fermentation
times and are presented in Table 1. Two species
of lactic acid bacteria (Lactobacillus and Pediococcus) were
identified. Three strains of Lactobacillus were isolated, Lact.
lactis subsp. lactis, Lact. brevis and Lact. cellobiosus. Lactobacillus
lactis subsp. lactis was isolated and identified from
both sorghum varieties (Bayadh and Hamra), while Lact.
brevis and Lact. cellobiosus were isolated and identified only
from the Hamra variety. The Pediococcus isolates were identified
as Ped. pentosaceus and were found in both sorghum
varieties. Pediococcus pentosaceus was dominant at the end of
the fermentation and maintained a high number.
The coliforms are listed in Table 1. Klebsiella pneumoniae,
Kl. oxytoca, Enterobacter aerogenes, Ent. sakazakii and Serratia
marcescens were found in both sorghum varieties. Serratia
odorifera was found in the Bayadh variety only.
Yeasts (Table 1) were identified as Candida parapsilosis, C.
norvegnsis and Rhotorula glutinis. Candida norvegnsis was
found only in the Bayadh variety. Moulds (Table 1) were
identified as Rhizopus sp., Penicillium sp., Alternaria sp., Apergillus
niger, Mucor sp. and Fusarium sp.
DISCUSSION
There were several micro-organisms that are found naturally
in sorghum flour. These micro-organisms included coliforms,
lactic acid bacteria, yeasts and moulds. Chavan and Kadam
(1989) have indicated that the micro-organisms involved in
Table 1 Micro-organisms isolated during khamir fermentation
—––––––––––––––––––––––––––––––––––––––––––––––––––– ––
Bacteria Yeasts and moulds
—––––––––––––––––––––––––––––––––––––––––––––––––––– ––
Lactic acid bacteria n Yeasts n
Pediococcus pentosaceus (8) Candida parapsilosis (10)
Lactobacillus brevis (2) C. norvegnsis (1)
Lact. lactis subsp. lactis (4) Rhodotorula glutinis (2)
Lact. cellobiosus (3)
Coliforms n Moulds n
Klebsiella oxytoca (1) Penicillium sp. (4)
Kl. pneumoniae (3) Rhizopus sp. (1)
Enterobacter aerogenes (1) Aspergillus niger (1)
Ent. sakazakii (4) Alternaria sp. (1)
Serratia marcescens (2) Fusarium sp. (2)
Ser. odorifera (1) Mucor sp. (1)
—––––––––––––––––––––––––––––––––––––––––––––––––––– ––
the natural fermentation of cereals are essentially the surface
flora of seeds. The Enterobacteriaceae are common on plant
material. Members of the Enterobacteriaceae were found in
natural fermentations of different products such as sorghum
(Nout 1991; Mohammed et al. 1991) and soybeans (Mulyowidarso
et al. 1989). In the first sorghum fermentation, numbers
of coliforms remained constant. However, in the second
and third fermentations, coliforms were not detected after
12 h and 8 h, respectively. Similar results were reported by
Mica (1955), Nout et al. (1989), Nout (1991) and Mohammed
et al. (1991). Mohammed et al. (1991) suggested that Enterobacter
may be inhibited by the growth of lactic acid bacteria
which outnumber the Enterobacter and result in faster acid
production.
The numbers of lactic acid bacteria increased with time and
dominated the fermentation (Fig. 1a,c). Chavan and Kadam
(1989) indicated that lactic acid bacteria constitute the predominant
flora in the natural fermentation of water/cereal
meal mixture. Some of the lactic acid bacteria that were
isolated and identified in this study were isolated from different
fermented foods. Lactobacillus brevis has been isolated
from ‘tef’ (Gashe 1987), ‘fufu and ogi’ (Adegoke and Babalola
1988) and kisra (Mohammed et al. 1991). Lactobacillus cellobiosus
was isolated from fermented corn meal (Fields et al.
1981), and Ped. pentosaccus was isolated from kisra (Mohammed
et al. 1991). The increase in lactic acid bacteria resulted
in increased amounts of lactic acid produced and lower pH.
Similarly, in the natural fermentation, there was an increase
in the amount of lactic acid produced and a decrease in pH.
However, in the second and third fermentations, the amount
of acid produced was higher and the drop in pH was faster.
The faster drop in pH was probably due to the higher number
of lactic acid bacteria in the inoculum than the initial fermentation.
Similar results were obtained by Nout (1991) and
Mohammed et al. (1991). Therefore, the presence of lactic
acid bacteria is important in khamir production.
Numbers of yeasts and moulds remained constant during
the fermentation for both varieties, except for a slight decrease
during the third fermentation. Candida parapsilosis and
Rhodotorula glutinis were isolated from both Bayadh and
Hamra. Candida norvegnsis was isolated from Bayadh only.
Yeasts were isolated from different indigenous fermented
foods such as kisra, ogi, fufu, tef, burukutu and merissa
(Steinkraus 1983; Gashe 1987; Adegoke and Babalola 1988;
Chavan and Kadam 1989; Mohammed et al. 1991).
In conclusion, this study has shown that there are some
micro-organisms that are naturally present in sorghum flour.
During khamir fermentation, these micro-organisms result
in some microbial and biochemical changes. Changes in pH
and acidity were due to the outgrowth of lactic acid bacteria
which become the predominant organisms. Additional work
is needed on the use of isolated micro-organisms for the
development of starter cultures for khamir production.
© 1999 The Society for Applied Microbiology, Journal of Applied Microbiology 86, 221–225