THESE UNIQUE El Hassane Kéhien-Piho TOU - Nutridev

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ARTICLE IN PRESS
E.H. Tou et al. / LWT 40 (2007) 1561–1569
Results were compared with those obtained with the
traditional millet-based ben-saalga (control) previously
described in Tou et al. (2006).
2.4. Preparation of gruels
Gruels were prepared at different DM contents by
boiling the fermented paste for at least 5 min. However, to
prepare gruels with high ED, a longer cooking time
(10–20 min) was sometimes required to concentrate the
gruel.
2.5. Fermentation kinetics
2.5.1. Sampling
In order to describe the fermentation kinetics during the
soaking and settling steps, all experiments were performed
at ambient temperature and at laboratory scale using the
same utensils as those used by traditional producers.
Samples were taken during the soaking step (from 0 to
16 h) and the settling step (from 0 to 24 h), and frozen until
analyses.
2.5.2. Changes in pH
The pH was recorded online using a pH-meter (WTW
340i, Fisher Bioblock Scientific, France). Data were then
transferred onto an Excel file.
2.5.3. Changes in sugar concentrations
Mono- and disaccharides (glucose, fructose, maltose and
melibiose) were extracted from samples and their contents
were determined by High Performance Ionic Chromatography
(Dionex DX 500 apparatus using a Carbo PA1
column). Detection was made by pulsed amperometry.
Experimental conditions are detailed in Tou et al. (2007).
The results are expressed in mmol/l.
2.5.4. Changes in lactic and acetic acid and ethanol
concentrations
Ethanol, lactic and acetic acid contents of samples taken
during the soaking and fermentation steps were determined
by HPLC according to the method described by Calderon,
Loiseau, and Guyot (2001). The results are expressed in
mmol/l.
2.6. Assessment of nutritional value
2.6.1. Proximate composition
Protein content was determined according to the
AFNOR NF V03-050 standard method (AFNOR, 1970)
based on determination of nitrogen content with the
Kjeldahl method with a conversion factor of 6.25. Lipid
content was determined with the HT6 Soxtec system
(Tecator, Ho¨gana¨s, Sweden) according to the application
note Tecator No. 3144. Ash content was measured after
calcination in a furnace at 530 1C. Acid Detergent Fibre
(ADF) contents (cellulose and lignin) were determined
using the gravimetric method of Van Soest (1963) with a
Dosi-fiber (Selecta, Barcelona, Spain). Available carbohydrate
contents were obtained by difference. The energy
value was then calculated using the coefficients of 4 kcal/g
DM for proteins and available carbohydrates, and 9 kcal/g
DM for lipids, and expressed in kcal/100 g of DM of the
gruel.
2.6.2. Energy density
The consistency of gruels was assessed using a Bostwick
consistometer (CSC Scientific Company Inc., Fairfax,
Virginia, USA) (Mouquet, Greffeuille, & Tre` che, 2006).
Measurements were made at 45 1C and the Bostwick flow
value was expressed in mm/30 s. DM content of gruels were
determined by oven-drying at 105 1C to constant weight.
The ED of the gruel was calculated at a Bostwick flow of
120 mm/30 s, corresponding to a suitable consistency for
young children (Vieu, Traore´, & Trèche, 2001), by multiplying
the gruel DM content by its energy value, and
expressed in kcal/100 g of gruel.
2.6.3. Phytate content
Phytate was extracted from 0.2 g of sample treated with
10 ml of 0.5 M HCl. The phytate content was estimated by
determination of myo-inositol hexaphosphate (IP6) content
obtained by anion exchange HPLC separation, according
to the method of Talamond, Gallon, and Trèche (1998).
2.7. Enumeration of mesophilic aerobic bacteria, lactic acid
bacteria, amylolytic lactic acid bacteria and yeasts
Bacteria and yeasts were counted in samples of pastes
taken after 0, 4, 8 and 24 h of fermentation. Aerobic
mesophilic bacteria, LAB, ALAB and yeasts were counted
on, respectively, plate count agar (PCA, Difco), de Man,
Rogosa and Sharpe (MRS, Difco), modified MRS (without
tween 80, glucose was replaced by soluble starch at 20 g/l)
and Yeast Glucose Chloramphenicol (YGC, Oxoid), in the
conditions described by Tou et al. (2006).
2.8. Statistical analysis
Each experiment was replicated three times. All analyses
and counts were done in duplicate and the two resulting
values were averaged. Data were submitted to analysis of
variance (ANOVA), using the general model procedure of
STATGRAPHIC Plus version 5.1. Statistical differences
between means (Po0.05) were tested by Duncan’s multiple
range test (Duncan, 1955).
3. Results and discussion
3.1. Fermentation kinetics
3.1.1. Soaking step
Changes in pH and concentrations of sugar, ethanol, lactic
and acetic acids: During the soaking of the millet and of the