Contribution à la mise au point de nouveaux matériaux membranaires pour la filtration de milieux complexes : étude physico-chimique de membranes d'acétate de cellulose et de méthylcellulose partiellement alkylée obtenues par immersion-précipitation

In response to today's consumer seeking for high quality oil with an authentic stamp, membrane processing are part of the "mild technologies" looked for, both economically and quality wise. In the present study hydrophobicity is considered as the key for the separation. In the present work, a fractionation device having four compartments allowed the separation of an oil-in-water model emulsion through two commercial membranes of different hydrophobicity. A theoretical model of a hydrophilic/hydrophobic junction was proposed which allows the one way flow of molecules compatible with the barrier surface. In order to create an hydrophobicity scale between the two commercial membranes, new membrane materials must be synthesized. A third membrane was then synthesized from the ternary system of cellulose acetate/acetone/water by the immersion precipitation process. Small angle light scattering measurements defined a nucleation and growth mechanism ruling the phase separation. Further modification of the membranes was conducted by the incorporation of hydrophobically modified methylcellulose through its bond with epoxydodecane aliphatic chains. Membrane surface analysis by ATR-FTIR revealed an absorbance amplification in the alkyl stretching region. XPS high resolution spectra confirmed these observations by the increase of the carbon percentage in alkyl function C-(C,H). Membranes need further hydrophobic modifications in order to obtain better filtration resultsEn réponse aux exigences actuelles du consommateur qui recherche une huile authentique et de qualité, les procédés membranaires font partie des technologies douces recherchées avec l'avantage d'être économiques. L'étude menée a considéré l'hydrophobicité de surface comme clé de la séparation. Un module de fractionnement à quatre compartiments a permis la séparation d'une émulsion modèle à travers deux membranes commerciales de polarité différente. Un modèle théorique de jonction hydrophile/hydrophobe est alors proposé, dans lequel la séparation se fait par passage unidirectionnel des molécules compatibles avec la membrane barrière. La synthèse de nouveaux matériaux membranaires générant une échelle d'hydrophobicité entre ces deux membranes aux propriétés extrêmes est lors visée. Une troisième membrane a donc été synthétisée à partir du système ternaire acétate de cellulose/acétone/eau par immersion-précipitation. L'étude par diffusion statique de la lumière aux petits angles a permis de déterminer un mécanisme de nucléation et croissance des membranes. Ces membranes sont ensuite modifiées par incorporation de méthylcellulose alkylée avec les chaînes aliphatiques d'époxydodécane. Les spectres infrarouges en mode de réflexion totale atténuée des membranes modifiées montrent une amplification de l'absorbance dans la région des vibrations d'élongation des chaînes alkyles. Les spectres haute résolution en XPS des membranes modifiées confirment ce résultat par une augmentation du pourcentage de la composante du carbone des chaînes alkyles C-(C,H). Une accentuation du caractère hydrophobe de la membrane est recherchée afin d'obtenir les résultats souhaités en filtratio

Durum Wheat Couscous Grains: An Ethnic Mediterranean Food at the Interface of Traditional Domestic Preparation and Industrial Manufacturing

International audienceCouscous is the product prepared from durum wheat semolina that agglomerates by adding water and undergoes physical and thermal treatment. Couscous is a traditional food from Mediterranean countries consumed for many centuries. Between ancestral domestic practices and industrial performance, the diversity of methods for couscous processing meets the needs of different consumers, whether they are concerned about preserving family culinary traditions or discovering innovative foods that respond to changing consumption patterns. In this work, we present the story of durum wheat couscous through several complementary visions and approaches: a “historical and societal“ approach to discover the origins of couscous, its migrations and its unifying role in Mediterranean societies; a “physicochemical” approach to describe the role of wheat components at the heart of couscous grains; a “technological” approach to compare domestic and industrial production of couscous; a “food science” approach to understand organoleptic characteristics of couscous grains; and a “consumer” approach to understand the motivations associated with the consumption of couscou

Study of culinary sayings in traditional Lebanese recipes by means of molecular gastronomy

National audienc

De nouveaux procédés d’extraction des huiles pour des produits finis de haute qualité

New concerns have appeared recently from the European and American consumers about quality, safety and environmental impact of the food products. In the particular case of European countries, the coming back of traditional products with a high sentimental value should be noticed. To fit the forthcoming demand of the consumer, the Oils and Fats industry have to develop a new approach based on alternative technologies that may emerge from the research with very specific objectives: no solvents, mild technologies, less energy consumption and final wastes. The purpose of this article is to discuss about the new biological tools capable to generate alternative ways for the oil elaboration: use of enzymes for destructuration of the vegetal or animal tissues and the subsequent utilisation of membrane techniques for the separation and purification steps. These new technologies involving less heat and mechanical stress to the oil, lead to a better “native” quality of the final products. However, fundamental research is needed on the separation mechanisms of those complex mixtures to optimise the process and prepare the transfer to the industrial conditions. The present article reports a contribution on the aqueous extraction of rapeseed oil as an exampl

Study of culinary sayings in traditional Lebanese recipes by means of molecular gastronomy

International audienc

Emulsifying properties of Acacia senegal gum: Impact of high molar mass protein-rich AGPs

The impact of high molar mass protein-rich arabinogalactan-proteins (AGPs) on emulsifying properties of Acacia senegal gums were studied using reconstituted gums obtained with two distinct fractions: one containing these specific high molar mass AGPs and the other protein-poor low molar mass AGPs. To produce and stabilize limonene emulsions, the experimental design emphasized not only the role of high molar mass protein-rich AGPs, but also the importance of high total concentration. At low protein contents, reconstituted gums required a slightly higher content in high molar mass protein-rich AGPs than original A. senegal gum, that confirmed the role of low molar mass protein-rich AGPs in the adsorption at interfaces. The comparison of the creaming index between original and reconstituted gums as well as the monitoring of instability phenomena by turbiscan up to 30 days clearly demonstrated the prevalent impact of the bulk apparent viscosity in the long-term stability of emulsions

Les membranes en lipotransformation : bilan, résultats, perspectives

Membrane separative techniques as candidates for alternative “green” processing of Oils and Fats present several advantages like energy saving, friendliness to environment and quality preservation of the final products. However, despite the considerable number of research programs carried out on several steps of the processing, including refining, desolvantisation and fractionation, no significant industrial development has been observed. Pointing out the lack of fundamental understanding of the mechanisms that rule the separations in hydrophobic media, a renewed approach of the membrane partition based on the relative hydrophobicity of lipids molecules vs barrier materials has been set up. Starting from an electronic analogy, a hydrophobic/hydrophilic valve has been designed by using a polar molecules coating on a porous material surface. The experimental realisation based on a two-compartments cell allowed to obtain preliminary results on the separation of the oily and water phases of an emulsion, that is a very promising result

Effect of whey powder rehydration and dry-denaturation state on acid milk gels characteristics

International audienceProtein enrichment of the milk base as well as heat treatment are two inevitable practices in yogurt formulation. In this study, the native and denatured whey protein isolates (WPI) powders by dry-heating were studied to elucidate their rehydration mechanism and the potential effect of dry-denaturation on acid gel formation. The added native or denatured WPI powders were allowed to rehydrate into the milk bases at various time ranges (5, 180, 300, 480, 900, and 1,440min). Rehydration kinetic of these powders was monitored by tracking particles size variation via the Qicpic granulo-morphometer. WPI rehydration into the milk base turned to be a quick two-step process. While rehydration condition seems not to affect the gel characteristics while, dry denaturation from its parts appears to delay onset of gelation and weakness the acid-gel elasticity. Practical applicationsCommercial preparation of yogurt involves different processing steps. Among them, protein fortification of the milk base as well as heat treatment appears as crucial steps that attribute towards the change in textural properties. Rehydration of the added powder is realized by the industry before applying the corresponding heat treatment, permitting thus to limit grainy texture. Throughout heating in the milk base whey protein isolates are denatured resulting thus in increased firmness. These aspects are of high significance in the preparation of dairy products, that is, different type of set and stirred yogurts, and this study shows that whey protein fortification is beneficial in their native form rather than in a dry-denatured form. On the other hand, their rehydration mechanism appears to be so fast, requiring few seconds permitting thus to limit the industrial usual time of rehydration (of 3hr) before further treatment