Isabelle Rochette

Anion-exchange high-performance liquid chromatography with conductivity detection for the analysis of phytic acid in food.

A sensitive method for the accurate determination of phytic acid in food samples is described. The proposed procedure involves the anion-exchange liquid chromatography with conductivity detection. Initially, two methods of determination of phytic acid were compared: absorptiometry and high-performance ion chromatography (HPIC) with chemically suppressed conductivity detector. Unlike most conventional methods involving precipitation by FeCl3, the simpler and more reliable HPIC assay avoids the numerous assumptions inherent in the iron precipitation and the accuracy is independent of the phytate content. The protocol was also applied to a survey of phytic acid concentration in some cereal, oil and legume seeds.

Ability of Selected Lactic Acid Bacteria to Ferment a Pearl Millet–Soybean Slurry to Produce Gruels for Complementary Foods for Young Children

To assess the ability of lactic acid bacteria to improve some nutritional characteristics of the pearl millet-soybean slurry to prepare complementary foods for young children in African countries, inoculation was performed using strains previously selected for their ability to hydrolyse starch, phytate, or alpha-galactooligosaccharides (alpha-GOS). For the sake of comparison with the action of a natural microflora, fermentation was also performed by back slopping inoculation, that is, with a sample obtained from spontaneously fermented traditional pearl millet slurry obtained from a small scale processing unit in Burkina Faso (Ouagadougou). Starter cultures thrived on the slurry as shown by counts on MRS agar, TTGE fingerprints, and fermentation patterns. The fermentation of precooked slurries inoculated by back slopping or with mixed cultures containing the amylolytic strain Lb. plantarum A6 enabled partial starch hydrolysis. Corresponding gruels had a suitable consistency for young child feeding at high dry matter content, and a high energy density: 88.7 +/- 4.2 and 75.8 +/- 5.1 kcal/100 g of sweetened gruel, for the gruels inoculated by back slopping or with Lb. plantarum A6, respectively. Unexpectedly, no decrease in phytates was observed in any of the experiments, suggesting the presence of one or more inhibitory compounds in soybean. Furthermore, preprocessing conditions before fermentation affect the carbohydrate composition of slurry and have a more profound effect than fermentation on the reduction of the alpha-GOS content.

Potential of amylolytic lactic acid bacteria to replace the use of malt for partial starch hydrolysis to produce African fermented pearl millet gruel fortified with groundnut

Fermentation and starch hydrolysis of a pre-cooked pearl millet-groundnut (MG) slurry inoculated with amylolytic lactic acid bacteria (ALAB) or by back slopping was investigated as a substitute for the addition of malt to prepare infant gruels. The ALAB collection strain Lb. plantarum A6, and the endogenous microflora provided by back slopping were more efficient in acidifying and partially hydrolysing starch in the MG slurry than Lb. plantarum 6.1, isolated from the traditional process in Burkina Faso. Large amounts of maltotriose and maltotetraose accumulated in slurry fermented by strain A6. No accumulation of maltose was observed, which could be an advantage to prevent the growth of microbial contaminants such as yeasts. Starch hydrolysis in the MG slurry inoculated with strain A6 or by back slopping enabled preparation of high-energy density gruels (84.7+/-4.4 and 80.4+/-23.8 kcal/100 g of gruel, respectively) of liquid consistency. However variability was higher with back slopping.

Changes in iron, zinc and chelating agents during traditional African processing of maize: Effect of iron contamination on bioaccessibility

The effect of the different unit operations of processing traditionally used to produce four maize foods commonly consumed in Africa on the nutritional composition of the products was investigated, using Benin as a study context. The impact of the processes on lipid, fibre, phytate, iron and zinc contents varied with the process. The lowest IP6/Fe and IP6/Zn molar ratios, the indices used to assess Fe and Zn bioavailability were obtained in mawè, a fermented dough. Analysis of maize products highlighted a significant increase in iron content after milling, as a result of contamination by the equipment used. Evaluation of iron bioaccessibility by in vitro enzymatic digestion followed by dialysis revealed that the iron contamination, followed by lactic acid fermentation, led to a considerable increase in bioaccessible iron content. Extrinsic iron supplied to food products by the milling equipment could play a role in iron intake in developing countries.

Consumption pattern, biochemical composition and nutritional value of fermented pearl millet gruels in Burkina Faso

Ben-kida and ben-saalga are popular pearl-millet-based fermented gruels in Burkina Faso. A survey of 318 households in Ouagadougou (Burkina Faso) showed that they are often used as complementary food for young children. Pearl millet and gruels, sampled in 48 production units, were analysed for proximate composition, factors reducing nutrient bioavailability (phytate, insoluble fibres and iron-binding phenolic compounds), α-galactosides, sugars, total lactic acid and d-lactic acid, zinc and iron contents. The effects of processing of pearl millet into fermented gruel are discussed. Both positive effects (e.g. a decrease in factors reducing nutrient bioavailability or α-galactosides) and undesirable effects (e.g. considerable lipid, protein, iron and zinc losses) were observed. Lactic acid was produced during processing and d(−)-lactate was detected in all samples. The gruels had very low energy density, even after addition of sugar, and low lipid, protein and mineral contents, well below recommendations for complementary foods.

Influence of flour blend composition on fermentation kinetics and phytate hydrolysis of sourdough used to make injera.

The influence of cereal blends, teff-white sorghum (TwS), barley-wheat (BW) and wheat-red sorghum (WrS), on fermentation kinetics during traditional fermentation of dough to prepare injera, an Ethiopian traditional fermented pancake, was investigated in samples collected in households. Barley malt was used with BW and WrS flours. WrS- and BW-injera sourdough fermentations were characterised by a transient accumulation of glucose and maltose and a two-step fermentation process: lactic acid fermentation and alcoholic fermentation with ethanol as the main end product. Only transient accumulation of glucose was observed in TwS-injera, and equimolar concentrations of lactic acid and ethanol were produced simultaneously. Final α-galactoside concentrations were low in all sourdoughs. Phytic acid (IP6) was completely hydrolyzed in WrS and BW-injeras probably due to the combined action of endogenous malt and microbial phytases. Only 28% IP6 hydrolysis was observed in TwS injera. Ways to improve IP6 hydrolysis in TwS-injera need to be investigated.

Fermentation by Amylolytic Lactic Acid Bacteria and Consequences for Starch Digestibility of Plantain, Breadfruit, and Sweet Potato Flours

UNLABELLED The potential of tropical starchy plants such as plantain (Musa paradisiaca), breadfruit (Artocarpus communis), and sweet potato (Ipomoea batatas) for the development of new fermented foods was investigated by exploiting the capacity of some lactic acid bacteria to hydrolyze starch. The amylolytic lactic acid bacteria (ALAB) Lactobacillus plantarum A6 and Lactobacillus fermentum Ogi E1 were able to change the consistency of thick sticky gelatinized slurries of these starchy fruits and tubers into semiliquid to liquid products. Consequently, a decrease in apparent viscosity and an increase in Bostwick flow were observed. These changes and the production of maltooligosaccharides confirmed starch hydrolysis. Sucrose in sweet potato was not fermented by strain A6 and poorly fermented by strain Ogi E1, suggesting possible inhibition of sucrose fermentation. In all 3 starchy plants, rapidly digestible starch (RDS) was higher than slowly digestible starch (SDS) and resistant starch (RS) represented between 17% and 30% dry matter (DM). The digestibility of plantain was not affected by fermentation, whereas the RDS content of breadfruit and sweet potato decreased and the RS content increased after fermentation. PRACTICAL APPLICATION The characteristics resulting from different combinations of gluten free starchy plants (plantain, breadfruit, sweet potato) and amylolytic lactic acid bacteria (ALAB) offer opportunities to develop new functional fermented beverages, mainly for breadfruit and sweet potato, after further investigation of their formulation, sensory attributes, nutritional, and prebiotic characteristics.

Determination of expression and activity of genes involved in starch metabolism in Lactobacillus plantarum A6 during fermentation of a cereal-based gruel

Traditional fermented gruels prepared from cereals are widely used for complementary feeding of young children in Africa and usually have a low energy density. The amylase activity of some lactic acid bacteria (LAB) helps increase the energy content of gruels through partial hydrolysis of starch, thus enabling the incorporation of more starchy material while conserving the desired semi-liquid consistency for young children. Even if this ability is mainly related to the production of alpha-amylase (E.C. 3.2.1.1), in a recent molecular screening, genes coding for enzymes involved in starch metabolism were detected in the efficient amylolytic LAB Lactobacillus plantarum A6: alpha-glucosidase (E.C. 3.2.1.20), neopullulanase (E.C. 3.2.1.135), amylopectin phosphorylase (E.C. 2.4.1.1) and maltose phosphorylase (E.C. 2.4.1.8). The objective of this study was to investigate the expression of these genes in a model of starchy fermented food made from pearl millet (Pennisetum glaucum). Transcriptional and enzymatic analyses were performed during the 18-h fermentation period. Liquefaction was mainly caused by an extracellular alpha amylase encoded by the amyA gene specific to the A6 strain among L. plantarum species and found in both Lactobacillus amylovorus and Lactobacillus manihotivorans. The second most active enzyme was neopullulanase. Other starch metabolizing enzymes were less often detected. The dynamic detection of transcripts of gene during starch fermentation in pearl millet porridge suggests that the set of genes we investigated was not expressed continuously but transiently.

Enzymatic degradation of phytate, polyphenols and dietary fibers in Ethiopian injera flours: effect on iron bioaccessibility.

The effect of removing phytate (IP6), iron-binding polyphenols, and dietary fibers on iron bioaccessibility in wheat-red sorghum (WrS) and teff-white sorghum (TwS) flour blends used in Ethiopia to make injera, a fermented pancake, was evaluated through the application of exogenous enzymes. Phytase treatment led to >90% reduction in IP6 and to an IP6:Fe molar ratio <1, but iron bioaccessibility was not improved (P > 0.05). Phytase + xylanase + cellulase (P + X + C) treatment increased iron bioaccessibility in TwS (non-detectableto1.6%) and WrS (1.9-3.2%), whereas phytase + polyphenol oxidase (P + PPO) treatment only showed improvement in the TwS blend. P + X + C + PPO treatment of the WrS blend increased the soluble non-dialysable iron fraction (6.7%) more than P + PPO treatment (3.9%). Although responses to enzyme treatments and iron bioaccessibility were matrix dependent, a positive effect of dietary fiber hydrolysis with X + C was obtained, irrespective of the blend. Dietary fibers had a negative effect on iron bioaccessibility independent of phytates.

Rapid quantification of iron content in fish sauce and soy sauce: a promising tool for monitoring fortification programs.

Background In a number of Southeast Asian countries and China, fish sauce and soy sauce produced at the industrial level are fortified with iron. Unfortunately, the food producers and regulatory agencies implementing fortification programs do not always have the capacity to monitor the programs on an ongoing basis. Objective To assess a new portable device for the quantitative measurement of iron content of fortified sauces that could be used to control fortification levels. Methods The linearity, detection limits, and inter- and intraassay variability of this device were assessed on fish sauce and soy sauce fortified with ferrous sulfate, ferrous fumarate, and sodium iron ethylenediaminetetraacetate (NaFeEDTA); the accuracy of the results was determined by comparing them with the results obtained by atomic absorption spectrophotometry. Results Measurements required a minimum incubation time of 1 hour for iron sulfate or iron fumarate and 24 hours for NaFeEDTA. Linearity of the results ranged from 2 to 10 mg iron/L for ferrous sulfate or ferrous fumarate and from 1 to 10 mg iron/L for NaFeEDTA, implying the need for proper dilution, as the iron contents of fortified sauce are usually in the range of 150 to 1,000 mg/L. Depending on incubation time, iron compounds, and sauces, the coefficient of variation (CV) of intraassay precision was between 1.5% and 7.6% and the CV of interassay precision was between 2.9% and 7.4%. Comparison with results from atomic absorption spectrophotometry showed high agreement between both methods, with R = 0.926 and R = 0.935 for incubation times of 1 hour and 24 hours, respectively. The Bland—Altman plots showed limits of agreement between the two methods of ± 70 mg/L in the range of fortification levels tested (100 to 500 mg/L). Conclusions This device offers a viable method for field monitoring of iron fortification of soy and fish sauces after incubation times of 1 hour for ferrous sulfate or ferrous fumarate and 24 hours for NaFeEDTA.