THESE UNIQUE El Hassane Kéhien-Piho TOU - Nutridev

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E.H. Tou et al. / International Journal of Food Microbiology 106 (2006) 52–60
mmol/l
12
10
8
6
4
2
0
0 2 4 6 8 10 12 14 16 18 20 22 24
Settling time (h)
glucose fructose maltose
sucrose raffinose melibiose
stachyose
Fig. 6. Kinetics of sugar consumption in supernatant during settling in pilot
scale experiments. Bars indicate standard deviation.
the ANF responsible for digestive disorders, their degradation
was also investigated to establish if they are eliminated
naturally during processing.
In contrast to phytates, the raffinose content in the grains
decreased mainly during the soaking step probably due to the
combined effect of diffusion and a-galactosidase activities.
However, even if ANF content does naturally decrease during
processing, ben-saalga, like many other traditional complementary
foods (Lorri and Svanberg, 1993, 1994; Trèche and
Mbome, 1999), is a diluted gruel that does not have the
necessary energy and nutrient density to fulfill the nutritional
requirements of infants and young children. To obtain a local
gruel with the required nutritional characteristics (Trèche,
1999; Lutter and Dewey, 2003; WHO, 1998), some modifications
of the traditional process will be necessary, taking into
account the skill of producers and thus relying on more detailed
knowledge of processing conditions. Notwithstanding, apart
from the nutritional aspects, more immediate benefits for the
Lactic acid and ethanol (mmol/l)
70
60
50
40
30
20
10
0
Unfermented wet flour
Fermented paste
Lac TPU Lac PSE Eth TPU Eth PSE
Fig. 7. Comparison of the changes in lactic acid (Lac) and ethanol (Eth)
concentrations in supernatant during settling between five traditional production
units (TPU) and pilot scale experiments (PSE). Bars are for standard
deviation.
Table 4
Counts of the aerobic mesophilic bacteria, lactic acid bacteria and yeasts in the
unfermented wet flour and fermented paste in 12 TPUs
Unfermented wet flour
(log CFU/mlTS.D.)
Fermented paste
(log CFU/mlTS.D.)
Aerobic mesophilic counts 6.5T0.4 7.1T0.4
Lactic acid bacteria (LAB) 6.2T0.9 7.0T1.1
Amylolytic acid bacteria (ALAB) 5.1T0.5
6.1T0.4
Yeasts 6.1T0.4 5.5T0.7
Ratio LAB/yeast 1.01 40.02
Ratio ALAB/LAB 0.10 0.12
LAB: lactic acid bacteria; ALAB: amylolytic lactic acid bacteria; S.D.: standard
deviation.
sanitary quality of the gruels resulting from the traditional
processing of pearl millet would be expected. The combination
of a decrease in pH to values lower than 4.0 during the settling
step, together with the simultaneous production of antimicrobial
compounds by LAB (lactic acid and possibly bacteriocins)
and a temperature near to boiling point during the final cooking
phase would limit contamination by food-borne pathogens
(Kingamkono et al., 1994; Lei and Jakobsen, 2004; Nout et al.,
1989; Nout and Motarjemi, 1997).
In spite of many studies describing the traditional processing
of cereals by lactic acid fermentation, detailed information
on fermentation kinetics is scant. In this study, particular
attention was paid to providing an accurate description of the
fermentation process combining observations made directly in
several TPUs and at the pilot scale. Ben-saalga processing
clearly includes two stages of fermentation, first alcoholic
fermentation during soaking and then lactic acid fermentation
during settling. The fact that lactic acid concentration is higher
than ethanol during the first 8 h of settling indicates the
metabolic heterogeneity of the LAB population, in which
homofermentative and heterofermentative pathways are simultaneously
active. Furthermore, it appears that from 8 to 24 h of
fermentation, only the homofermentative or facultative heterofermentative
LAB are active, suggesting a temporal variation in
the microflora.
High variability in the concentration of final products, such
as ethanol and lactic acid during soaking and settling,
respectively, was observed in the TPUs, and illustrates the
need to find a suitable strategy to better control processing
conditions. This is not only necessary to improve the
nutritional characteristics of the gruel but also to obtain a
foodstuff with constant food composition. This high variability
might be due to variations observed in the duration of the
different unit operations as shown in Fig. 1.
Whereas lactic acid fermentation is a classical phenomenon
during the settling step of cereal flours in many traditional
forms of processing, this is the first time that the soaking step
has been described in such detail and also associated with
alcoholic fermentation. This is consistent with the fact that
soaking the grains in water does not provide conditions
favorable for the growth of lactic acid bacteria which have
fastidious nutrient requirements, giving a competitive advantage
to microorganisms with less stringent nutritional requirements
such as some yeasts. In contrast, during settling nutrients
such as proteins and vitamins from pearl millet could be made