Restricted bovine serum albumin diffusion through the protein network of pasta

International audienceFood digestion may be influenced by the diffusion processes that govern the accessibility of substrates to enzymes

Influence of protein heat treatment on the continuous production of food foams

The influence of WPI heat treatment on the continuous production of food foams was investigated using a model food including xanthan. The temperature of heat treatment was increased up to 90 C using a plate heat exchanger; a rotor-stator unit was used for aeration purpose. The aim was to determine the interplay between heat-induced protein denaturation and aggregation, and the process parameters of aeration operation: namely, rotation speed, residence time and operating pressure. Microstructure, texture and stability of 200% overrun foams were analysed. Experimental results demonstrated that foam microstructure, namely overrun and bubble size distribution, was governed by the process parameters of aeration and depended only slightly on thermal treatment. Conversely, foam stability was strongly improved by heat treatment. These trends agreed roughly with results obtained in a batch kitchen mixer, but batch methods remained unable to predict quantitatively the behaviours observed in continuous aeration operation

Effet de la formulation sur l'élaboration de mousses laitières de type "topping"

Focus : Emulsions alimentaires foisonnéesNational audienc

Effect of dynamic heat treatment on the physical properties of whey protein foams

International audienceThe influence of dynamically heat-induced aggregates on whey protein foams was investigated as a function of the thermal treatment applied with the aim of determining the optimal temperature for the production of heat-induced aggregates dedicated to foaming. The native protein solutions (2% w/v WPI; 50 mM NaCl) at neutral pH were heat-treated using a tubular heat exchanger between 70 degrees C and 100 degrees C. Protein denaturation and aggregation were followed by micro-differential scanning calorimetry, size exclusion chromatography, laser diffraction and dynamic light scattering. The protein solutions were whipped using a kitchen mixer to produce foams. Foam overrun, stability against drainage, texture and bubble size distribution were measured. Experimental results showed that overrun slightly decreased with an increase of the temperature used to treat proteins, whereas foam rigidity was improved at the same time. An optimal temperature of thermal treatment was found at 80 degrees C for stability against drainage. Quantitative analyses showed that the formation of approximately 10% soluble aggregates in the WPI sample before whipping maintained a good level of overrun, lead to an increased stability against drainage and to an improved rigidity for whey protein foams. Conversely, they revealed that an increase of temperature above 80 degrees C before foaming did not improve anymore the functional properties of the proteins

Emulsification des bases laitières à foisonner par membrane : un procédé économe en énergie

National audienceThe tangential microfiltration is compared with high pressure homogenization of the sweetened milk bases designed to be foamed as topping (chantilly cream, i.e.). The hommgenization is known as being efficient for the refining of preemulsions, by producing a very important shear, unfortunately accompanied by an important heating. By the contrary, the microfiltration emulsification gives only a mild shear, with non noticeable heating. The emulsions have been foamed in a profiled rotor-stator device. The influence of membrane pores diameter, the flows of continuous and dispersed phases, the stabilizer type on the emulsification process has been studied. The results lead to the conclusion that membrane emulsification is a viable alternative to the classic foaming processes.La microfiltration tangentielle a été comparée à l'homogénéisation haute pression pour émulsifier des bases laitières sucrées destinées à être foisonnées sous forme de topping (du genre crème chantilly). L'homogénéisation est réputée très efficace pour affiner une préémulsion car elle procure un cisaillement extrêmement important, mais aussi un échauffement notable. Au contraire, l'émulsification par microfiltration ne met en jeu qu'un cisaillement faible et contrôlé puisqu'il correspond à l'entraînement, par la phase continue des gouttelettes de phase dispersée sortant des pores de la membrane. Les émulsions ont été foisonnées par un système rotor/stator à dents. Les facteurs étudiés lors de l'émulsification étaient le diamètre de pores de la membrane, 0.1 µm ou 0.5 µm, les flux respectifs de phase continue et de phase à disperser, et les types de stabilisants : la gélatine et un mélange d'hydrocolloides composé de xanthane, carraghénanes et guar. Les résultats montrent que le foisonnement est très sensible aux caractéristiques des émulsions; les émulsions fabriquées par microfiltration sur membrane de 0.1 µm ont des caractéristiques granulométriques et rhéologiques optimales pour un bon foisonnement ultérieur. En effet, même si ces émulsions ne sont pas aussi fines que celles fabriquées par homogénéisation hautes pressions, ceci sous-entend que l'aire interfaciale des globules gras est suffisamment peu élevée pour qu'il reste des protéines disponibles pour stabiliser les interfaces eau/air créées lors du foisonnement. Parmi ces émulsions foisonnées, celles qui proviennent d'émulsions stabilisées par des hydrocolloides manifestent des caractéristiques rhéologiques et des tailles de bulles telles qu'elles sont très fermes et stables. Ceci montre que le procédé d'émulsification par système à membrane représente une alternative sérieuse aux procédés traditionnels pour cette problématique

Effect of the heat-treatment on the physical properties of whey protein foams

National audienc

Combined effect of dynamic heat treatment and ionic strength on denaturation and aggregation of whey proteins - Part I

International audienceThe aim was to investigate the effect of dynamic thermal treatment in a heat exchanger on the denaturation and aggregation of whey proteins. A 2% w/v WPI solution (pH 7.0), with or without NaCl addition (100 mM), was submitted to heat treatment at 100 degrees C. At low ionic strength, a nearly complete denaturation was observed, while the heat-treated samples at 100 mM ionic strength registered only 10% denaturation. It was shown that not only denaturation was reduced by the presence of NaCl, but also that the size of the aggregates formed during heat treatment was far smaller and remained essentially below 1 mu m. Surface tension measurements showed a faster adsorption and lower sigma values for the non-polymerized proteins, whereas insoluble aggregates played only a poor role on the sigma curves. Finally, experimental results demonstrated the strong interaction between ionic strength and dynamic thermal treatment on protein aggregation and properties

Combined effect of dynamic heat treatment and ionic strength on the properties of whey protein foams - Part II

International audienceThe aim was to investigate the effect of dynamic thermal treatment in a tubular heat exchanger on the denaturation and foaming properties of whey proteins, such as overrun, foam stability and texture. A 2% w/v WPI Solution (pH 7.0), with and without NaCl addition (100 mM), was submitted to heat treatment at 100 degrees C. The results demonstrated that heat treatment slightly reduced overrun, whereas NaCl and heat treatment improved foam stability, enhanced texture and provided smaller bubble diameters with more homogeneous bubble size distributions in foams. The foaming properties of proteins, especially stability, were shown to depend not only on the amount of protein aggregates, but also on their size. While insoluble aggregates (larger than I pm diameter) accelerated drainage, soluble aggregates (about 200 nm diameter) played a key role on the stabilization of gas-liquid interfaces