Etat des connaissances et de la recherche sur la transformation et les utilisations alimentaires de l'igname.

Cet article présente une synthèse bibliographique des travaux concernant les utilisations alimentaires de l'igname à travers le monde. Les systèmes traditionnels de transformation de ce tubercule, ainsi que les initiatives semi-industrielles ou industrielles sont recensés. Cette synthèse montre que la transformation de l'igname a fait l'objet de recherches relativement limitées par rapport à la racine de manioc. De plus, ces travaux se sont souvent déroulés en laboratoire, sans véritable connexion ni application directe en entreprise, ni connaissance suffisante des réelles attentes des consommateurs. L'igname et ses dérivés sont toujours considérés comme chers et sont concurrencés par des produits importés. Par ailleurs, les études menées jusqu'ici se sont essentiellement focalisées sur quelques produits classiquement connus, tels que les pâtes élastiques (foufou et foutou), la farine et les flocons. Dans le but de relancer cette filière et de valoriser le potentiel nutritionnel, socio-économique et technique de ce tubercule, la diversification des produits à base d'igname paraît incontournable. Des recherches appliquées sont alors nécessaires pour, d'une part, améliorer les systèmes techniques de transformation à différentes échelles (artisanale, semi-industrielle et industrielle) et, d'autre part, mieux connaître et appréhender la demande des marchés et des consommateurs. Des pistes de recherche intéressantes et prometteuses se profilent actuellement. Celles-ci s'orientent vers une meilleure connaissance des caractéristiques variétales et de leur aptitude à la transformation afin de mieux cibler leurs utilisations technologiques potentielles, ainsi que vers la mécanisation de certaines étapes technologiques (épluchage, séchage...) qui interviennent dans la plupart des procédés de transformation. Enfin, l'élaboration de produits fermentés à base d'igname serait une voie de valorisation de ce tubercule, à l'instar de ceux fermentés à partir de manioc et reconnus pour leur valeur nutritionnelle

Heat and mass transfer investigation of rotating hydrocarbons droplet which behaves as a hard sphere

AbstractThe steady state boundary layer equations around rotating pure hydrocarbon droplet are solved numerically. The droplet is simulated to behave as a hard sphere. The transfer equations are discretized using an implicit finite difference method where Thomas algorithm solves the system of algebraic equations. Moreover, dimensionless parameters of heat and mass transfer phenomena around a rotating hexane droplet concluded. The thickness of the boundary layer is unknown for this model and therefore, it is determined. Further, this work proposes correlations of Nusselt and Sherwood numbers for monocomponent hydrocarbon droplets in evaporation. These correlations consider the rotation phenomena and further, the variation of the thermophysical and transport properties in the vapour phase

Effect Of The Hydraulic Diameter On Pressure Drop Across Restrictions Of A Tube Support Plate Used In Heat Exchangers

This paper presents experimental results for the pressure drop across an annular geometry restriction in a Tube Support Plate (TSP). These restrictions are typical in pressurized water reactor (PWR) steam generators. The pressure drops were experimentally measured for single and two-phase air-water mixture. This research compares the pressure drops for two different geometries (annular and trefoil) with the same hydraulic diameter (0.0906 inch) to determine if the hydraulic diameter is an appropriate geometric modeling parameter for this type of geometry. The loss coefficients were also determined and empirical correlations were developed. A conclusive comparison of the annular with trefoil geometries is provided and recommendations given. It is concluded that the hydraulic diameter is not an appropriate geometric modeling parameter. The annular geometry yields to a lower pressure drop than the trefoil geometry for the same hydraulic diameter. The tests were performed at atmospheric conditions

Dynamics of the microbial community responsible for traditional sour cassava starch fermentation studied by denaturing gradient gel electrophoresis and quantitative rRNA hybridization

The microbial community developing during the spontaneous fermentation of sour cassava starch was investigated by cultivation-independent methods. Denaturing gradient gel electrophoresis (DGGE) of partially amplified 16S rDNA followed by sequencing of the most intense bands showed that the dominant organisms were all lactic acid bacteria (LAB), mainly close relatives of #Bifidobacterium minimum, #Lactococcus lactis, #Streptoccocus sp., #Enteroccucus saccharolyticus and #Lactobacillus plantarum. Close relatives of #Lb. panis, #Leuconostoc mesenterides and #Ln. citreum were also found. A complementary analysis using hybridization of 16S rRNA with phylogenetic probes was necessary to detect the presence of the recently discovered species #Lb. manihotivorans$. Although it represented up to 13$. In addition, it was shown that a strong pH decrease in the time course of fermentation was most probably responsible for the competitive selection of acid-resistant LAB vs. both homo and heterofermentative acid-sensitive LAB. (Résumé d'auteur

Gari, a traditional cassava semolina in West Africa: its stability and shelf life and the role of water

Gari is a cassava semolina traditionally processed and widely consumed in West Africa. Its shelf-life is largely dependent on both its water content and storage temperature and relative humidity. This paper deals with gari`s adsorption properties in relation to water availability at 15, 25, and 30 degrees C. From the results, optimal packaging conditions can be estimated, thus providing an extended shelf-life for gari