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National audience; Ce programme a pour objectif de mieux cerner les évolutions de structure et de propriétés fonctionnelles subies par les concentrés protéiques laitiers au cours de leur élaboration, en lien avec les paramètres de procédés appliqués. L’influence du schéma technologique defabrication, de la base de mélange (eau vs perméat d’ultrafiltration de lait) et de la formulation sur les caractéristiques physico-chimiques etles propriétés de réhydratation ont notamment été évaluées. Les résultats montrent qu’à teneur en lactose et force ionique plus élevées, ladénaturation des protéines est moins prononcée après concentration par évaporation. De plus, les poudres à caséines majoritaires traitéesthermiquement présentent une granulométrie plus élevée que celles sans traitement thermique. Pour ces formules, le traitement thermiqueinduit une augmentation significative de la fraction volumique occupée par les protéines dans les concentrés aqueux avant séchage. Enfin,quelle que soit la formulation, le traitement thermique facilite la réhydratation des particules : ce phénomène est d’autant plus marquélorsque le taux de protéines solubles dans le mélange est plus élevé.

International audience; Dairy ingredients with highly concentrated protein contents are high added value products with expanding market. They are known to have specific properties adapted for a multitude of applications (cheese, bakery, infant formulae, nutritional products for the elderly and sportspeople...). Fabricationof such dairy protein ingredients is conducted by a succession of unit operations where heat treatment is a key step that induces major changes in protein structures and thus ingredients functionalities. However, due to an incomplete understanding of phenomena taking place at these high proteinconcentrations, shedding light on these mechanisms is simultaneously a scientific challenge and an industrial need. For this purpose, we used an original approach to investigate the influence of heat treatment and mineral environment of concentrated milk protein system on viscosity and enzymatic coagulation properties. Experiments were conducted with fresh whey protein isolates (WPI) and native phosphocaseinates (NPC) according to the ratio 20:80 (WPI:NPC) using 4 different technological routes: without heat treatment (Control); with one heat treatment at 10% w/w protein; with one heat treatment at 20% w/w protein and with two heat treatments at 10% and 20% w/w protein. Interestingly, the protein concentration of the heat-treated solution greatly modulates the denaturation and aggregation process of whey proteins, which modifies the association mechanismsbetween WPI and NPC. Indeed, the increase of protein content leads to a higher particles collision probability and a shorter inter-protein distance modifying protein-protein interactions. Furthermore, the nature of complexes formed during the heat treatment and the amount of aggregates present in solution are two parameters that can modulate the rheological properties (here viscosity and enzymatic coagulation ie, gel time and gel strength) of the system. Influence of lactose and mineral environment is discussed in a second time.

International audience

International audience

International audience; The evaporation of a colloidal dispersion is characterized by solute accumulation at the air-liquid interface, leading to the gradual formation of a gelled skin. From the preliminary colloid deposit to complete solidification, the development of this layer affects the overall drying process and final sample morphology. Despite progress in the last decades, the mechanisms governing skin formation in drying colloidal suspensions have not yet been fully clarified, especially in complex polydisperse systems. This work investigates droplet skin formation in a binary dairy proteins system, i.e. whey proteins isolates (WPI), and native phosphocaseinates (NPC). A single droplet approach was used to explore both droplet morphology evolution and drying kinetics as a function of WPI relative fraction in the overall protein content (WPI%R). The observation of the evaporation stages highlighted the separate role of WPI and NPC on drying dynamics, leading to two shape categories characterized by skin buckling (WPI%R≤20%) and rigid convex shell (WPI%R≥50%), respectively. Mainly, estimating droplet drying kinetics and sol-gel transition characteristic times highlighted WPI significant impact above a critical value (WPI%Rc), resulting in a rigid skin with high resistance to buckling. Such enhanced mechanical properties suggest WPI external segregation during skin formation, whose evidence was provided by the direct observation of dry skin section structure. The hypothesis of protein stratification by size was corroborated by the agreement with recent predictive models on the evaporation of bidisperse model colloidal suspensions. This study contributes to a better understanding of the competitive drying mechanisms occurring in binary colloidal systems.

International audience

International audience; The dairy powders production represents a significant portion of the market related to dairy industry. Controlling powder nutritional properties has become crucial due to the increasing number of end-users. So far, this question has been addressed taking advantage of the empirical experience gained in the last decades. However, a full understanding of the physics governing the droplet-to-particle transition in industrial dryers, which would be decisive for the tight control of the process, is far from being achieved. To this purpose, the single droplet approach has been used to explore the drying dynamics at the lab scale in dairy simplified model systems, such as mixes of the two milk proteins: the whey proteins (WPI), i.e. globular colloids, and the casein micelles (NPC), i.e. deformable sponge-like structures. In this work, we focused on the evaporation in droplets of WPI/NPC suspensions with different protein concentration (cp) and composition (WPI%R). We investigated the formation of the skin at the air-liquid interface and we explored the paradigm linking protein physico-chemical properties to skin rheology and, consequently, to final droplet shape. A general overview of the process was carried out observing droplet profile evolution and evaluating the drying kinetics by mass measurements. A characterization of the skin organization at the colloidal scale was provided by interfacial rheology, using the oscillatory drop method, and scanning electron microscopy. Our outcomes revealed the separate role of WPI and NPC in skin formation. Under certain conditions, we observed WPI segregation on the external part of droplet surface, which significantly affected dry particle shape. Our systematic approach allowed to obtain a phase diagram able to predict dry particle morphology for a wide range of cp and WPI%R. To summarize, our results represent a potential tool for the control of dairy powder characteristics and contribute also to the understanding of the evaporation in polydisperse colloid systems.

2.1 About 200 million tons of whey are produced worldwide each year, and the production is constantly increasing. Whey is a by-product rich in proteins, lactose and minerals, but its composition largely varies depending on its manufacturing process. To be valorized, whey is usually processed into whey powder, protein concentrate and lactose by a spray-drying step. However, the high level of organic acids in acid wheys has an influence on the amorphous form of lactose. Consequently, its hygroscopicity is greater and affects its behavior upon drying, leading to caking tendency and poorly rehydratable powder for further purposes. Pressure- and electrically driven membrane technologies are capable of fractionating the whey components to enhance its powder quality and obtain high-value products. In this chapter a quick presentation of the main membrane technologies will be given as well as an overview of research studies dealing with these technologies, prior to the drying step of whey, for demineralization, delactozation and/or deacidification. Depending on the case, the technology and the objective of the study, about 50–95% of minerals, 50–60% of lactose and 30–80% of lactic acid could be removed from the whey, enhancing its dryability and reducing drastically the energy consumption costs up to 40%.2.2 In the dairy industry, concentration by vacuum evaporation is widely used for the production of concentrated products, such as evaporated milk, sweetened condensed milk and concentrated yoghourt. It is also implemented as an intermediate step for the manufacture of powders. The operation is carried out predominantly in falling-film evaporators that can be considered as a combination of vertical shell-and-tube heat exchangers. This book chapter provides an overview of the vacuum concentration operation; it is composed of four main parts. Section 2.2.1 describes the working principles and the design of the evaporators directed towards energy savings. Section 2.2.2 focuses on the physicochemical and structural changes induced by the evaporation process, while Section 2.2.3 deals with the flow and heat transfer phenomena involved in the operation. Lastly, Section 2.2.4 discusses the fouling and cleaning of evaporators, as fouling problems occur after several hours of production runs as for any heat exchanger, requiring appropriate cleaning procedures to recover their optimal performances.2.3 Lactose crystallization in whey or permeate is a key stage in the manufacture of whey, permeate and lactose powders. Controlling this stage at an industrial level should increase the prospects of improving the process and also the physicochemical quality of powders. Lactose crystallization occurs in highly supersaturated solutions, indicating that the phenomena of nucleation and crystal growth can take place simultaneously. At an industrial level, lactose crystallization is also performed in a medium of complex chemical composition. Some macromolecules, such as whey proteins or mineral components, influence the kinetics of lactose crystallization. The presence of other components at each change of state can modify the kinetics. For a better understanding of their influence, it is necessary to determine their specific effects on lactose solubility and the laws of the kinetics controlling the stages of mutarotation, nucleation and growth, by taking into account the process–product interactions.2.4 The mechanical process of homogenization is involved in the manufacture of fat-filled spray-dried powders to disperse fat into individual droplets and assure their physical stability. This book chapter is structured in five main parts: Section 2.4.2 presents the mechanical process of homogenization; Section 2.4.3 discusses the position of the homogenization process in the technological scheme of spray-dried powder production; Section 2.4.4 examines the possible organizations of fat within spray-dried powders; Section 2.4.5 evaluates the potentialities of homogenization in the preparation of nanostructured lipid carriers, and Section 2.4.6 describes the key role played by homogenization in the preparation of dairy products such as infant milk formula and highlights the potentialities of homogenization for innovation in the near future.2.5 This chapter will firstly discuss some strategies in the control of the spray-drying process with reference to the multistage layout of the process. In particular, the discussion will center on the control of the outlet temperature, fines return and agglomeration, and in the manipulation of the spray feed viscosity. The different forms of spray-dryer modeling (one-dimensional and computational fluid dynamics simulations) will be introduced, and the capabilities and expected outcomes from these modeling frameworks will be discussed. The development of two unique techniques to better understand the spray-drying process will be introduced: the single-droplet drying and the monodisperse spray-drying techniques. These techniques are now commercially available, and the latter can be used to produce products with high uniform homogeneity in particle sizes. The last part of this chapter touches on the use of superheated steam as a potential drying medium in spray dryers. This new approach may offer the potential to produce powder with improved wettability.2.6 The agglomeration process has been widely used by the dairy industry for many years to produce instant powders with improved rehydration properties. The chapter provides an overview of the three main processes for the agglomeration of dairy powders (agglomeration during spray drying, fluidized-bed agglomeration and steam-jet agglomeration). For each of these technologies, we present the principle associated with the technology, the characteristics of the equipment, the mechanisms involved during agglomeration and the influence of process control factors on the characteristics and usage properties of the agglomerated powders.2.7 This chapter will explain a new concept and application for the fluidized-bed drying stage in dairy powder processing. The fluidized-bed dryer has been primarily used for powder conditioning, further reducing residual moisture content (secondary drying) from the spray dryer, and agglomeration. In this chapter, the crystallization (post-drying) and modification of particle microstructure and the physical properties of powders are described. The new application is designed based on conventional equipment, with minimal modification, to reduce the capital cost for implementation. Process integration and development based on the mathematical modelling of the underlying physics are covered. A new heterogeneous particle microstructure is introduced in which the particle is partially crystalized. Analytical results for product performance and physicochemical properties, and effects on stability and shelf life have been reported and discussed. The crystalline surface layers enhance the powder physico-chemical properties and shelf life, while the amorphous core maintains the rehydration and bioavailability

https://hal.archives-ouvertes.fr/hal-02424701; National audience; Le besoin de développer la nano-instrumentation intégrée de détection, à bas coût à haute sensibilité sur des principes de résonances est un défi majeur et crucial pour les domaines industriels de la cosmétique, de l’agroalimentaire, de la pharmacologie galénique, de la biologie, et du biomédical ; la nécessité étant d’assurer les diagnostiques à réaliser en termes d’analyses, de contrôle qualité et de sécurité des substances, des aliments, des médicaments en solutions, des lotions actives, des crèmes, des mousses... L’ensemble de ces états de la matière en chimie et physique se nomme la matière molle et ses changements les transitions d’états, de phases ou de consistances… A titre d’exemple non exhaustif dans le domaine de la pharmacologie galénique, certaines solutions fluides avec principes actifs incorporés en suspension seront actives tant que les éléments ne sédimentent pas ; caractéristique qui induirait une qualité moindre de la solution médicamenteuse ou bien une forme de péremption. Sur ce principe d’interaction matière-lumière résonante sur puce intégrée, des mesures fines sur la nouvelle plateforme et le suivi dynamique des dits produits et substances ont permis de détecter des transitions de phases (gel/fluide/mixe émulsion/poudre solide), de mesurer des vitesses de sédimentation et même des phénomènes et mécanismes comme le séchage, la floculation, les effets Marangoni, ou encore les effets spontanées d’émulsion encore incompris [1-3]…

Le besoin de développer la nano-instrumentation intégrée de détection, à bas coût à haute sensibilité sur des principes de résonances est un défi majeur et crucial pour les domaines industriels de la cosmétique, de l’agroalimentaire, de la pharmacologie galénique, de la biologie, et du biomédical ; la nécessité étant d’assurer les diagnostiques à réaliser en termes d’analyses, de contrôle qualité et de sécurité des substances, des aliments, des médicaments en solutions, des lotions actives, des crèmes, des mousses... L’ensemble de ces états de la matière en chimie et physique se nomme la matière molle et ses changements les transitions d’états, de phases ou de consistances… A titre d’exemple non exhaustif dans le domaine de la pharmacologie galénique, certaines solutions fluides avec principes actifs incorporés en suspension seront actives tant que les éléments ne sédimentent pas ; caractéristique qui induirait une qualité moindre de la solution médicamenteuse ou bien une forme de péremption. Sur ce principe d’interaction matière-lumière résonante sur puce intégrée, des mesures fines sur la nouvelle plateforme et le suivi dynamique des dits produits et substances ont permis de détecter des transitions de phases (gel/fluide/mixe émulsion/poudre solide), de mesurer des vitesses de sédimentation et même des phénomènes et mécanismes comme le séchage, la floculation, les effets Marangoni, ou encore les effets spontanées d’émulsion encore incompris [1-3]…

National audience

International audience; The production of milk powders is a strategic sector of the dairy industry. Due to its complex macromolecular composition, shedding light on the mechanisms governing milk drying constitutes a main industrial concern and a scientific challenge at the same time. In this study, we used the single droplet[1] and the directional drying[2] approaches to investigate the evaporation of colloidal mixes of the two major milk proteins (whey protein isolates and native phosphocaseinates). Notably, we observed the crack development in the samples to evaluate the competitive impact of the physico-chemical properties of whey proteins (rigid globular shape) and casein micelles (deformable sponge-like structure) on the drying process. Our outcomes are potentially useful to better control the functional properties of milk powders. Furthermore, they contribute to improve the understanding of the drying mechanisms in binary colloidal systems, which are still far from being fully elucidated.

International audience; Spray drying is a well-established process, but the phenomena ruling droplet-to-particle transition remain black box, resulting in variable powder properties and drying performances. Therefore, understanding precisely how the particle is formed and how to control its properties remain a major challenge. This work aims to breakdown the complexity of the drying phenomena using an exploratory multi-scale approach. Particle formation of different milk proteins (whey proteins and casein micelles) was investigated using different experimental systems (single pendant droplet, mono-dispersed droplets and spraying cone droplets) in controlled drying environments. The results showed that the drying of a single protein droplet included three distinct stages highlighting the occurrence of specific morphological events (constant rate shrinkage, buckling instability, vacuole nucleation). According to the type of proteins, these stages differed in drying kinetics and droplet dynamics, leading to characteristic and reproducible particle shapes irrespective of the droplet configuration and the drying conditions. These different drying behaviors were related to specific skin formation mechanisms at droplet air-liquid interface and consequent responses of the protein material to internal stresses. In this work, we aimed at understanding how the different physico-chemical properties of whey proteins (rigid globular shape) and casein micelles (deformable sponge-like structure) affect the mechanisms of formation of such a skin, and from this the particle final shape. However, the full understanding of the drying process of biocolloids is far to be achieved and, notably, the impact of solute properties on the morphological characteristics of the evaporating droplets, such as colloid segregation, skin formation and crack pattern development is not elucidated yet. To this aim, the use of model colloidal solutions, whose rheological behavior is more easily deducible, could represent a significant boost. Consequently, we compared the drying of droplets of whey proteins and casein micelles to that of dispersions of silica particles and polymer-coated silica particles, respectively. The mechanical behavior of such biological colloids and model silica dispersions was investigated through the analysis of crack formation, and the measurements of their mechanical properties using indentation testing. The study reveals numerous analogies between dairy and corresponding model systems, thus confirming these latter as powerful tools to highlight the signature of the matter on the drying process and at the molecular scale. The outcomes presented in this work represent a first step to shed light on the physics of drying dairy droplets; they open the road to further investigation about mixes of milk proteins. Moreover, the observation of mixtures of dairy colloids would contribute to improve the knowledge about the evaporation of colloidal polydisperse systems, which represents a current scientific challenge.

The production of dairy powders, involving high added value products such as high protein powders and infant milk formulas, has nowadays become strategic for the dairy industry. Due to their complex composition in terms of proteins and macromolecules, shedding light on the underlying mechanisms governing the evaporation of such dairy products constitutes a main industrial concern and a scientific challenge at the same time. In this study, we used the single droplet approach to investigate the evaporation of dairy solutions consisting of the two major milk protein components (whey proteins and native micellar caseins), alone or in mixes with different whey protein to casein ratio. In the works performed in our group in the last decade[1-3], we demonstrated that studying the drying of such biocolloidal systems at the single droplet stage is consistent to predict the behavior at larger industrial drying scale. We observed that the droplet-to-particle transition that characterizes the evaporation of dairy mixes consists of three main phases: pure shrinkage, skin formation and buckling, and finally end of the process. Here, we mainly focused on the gradual development of the droplet gelled skin due to the continuous sol-gel transition at the air-liquid interface (buckling stage). In particular, we aimed at understanding how the different physico-chemical properties of whey proteins (rigid globular shape) and casein micelles (deformable sponge-like structure) affect the mechanisms of formation of such a skin and therefore the particle final shape. To this end, we estimated in real-time the internal flows in drying droplets of whey protein and casein mixes by optical microscopy (particle tracking and particle image velocimetry). Simultaneously, the development of the skin due to the continuous solute migration was visualized by both optical and confocal microscopy. In addition, an elemental analysis by scanning electron microscopy was realized on the dried particle skin of the different mixes to extract further information about the specific deposition of the two colloidal components during the desiccation process. Our outcomes highlight the strong impact of both chemical composition and physical structure of whey proteins and casein micelles on the duration and the intensity of the internal flows during the drying of mixes, as well as on the mechanisms of organization of the external skin throughout the evaporation process. These results represent a promising progress in order to improve the control of the functional properties of milk powders. Furthermore, they contribute to improve the understanding of the drying mechanisms in binary colloidal systems, which are still far from being fully elucidated.

Mécanismes de formation de l’interface au cours du procédé de séchage : approche multiéchelles appliquée aux poudres laitières. journée scientifique "science des aliments et valorisation des bio-produits"

Spray-drying - concentrated matrices –functionalities team objectives. STLOpendays

International audience; The evaporation of colloidal solutions is frequently observed in nature and in everyday life. The investigation of the mechanisms taking place during the desiccation of biological fluids is currently a scientific challenge with potential biomedical and industrial applications. In the last few decades, seminal works have been performed mostly on dried droplets of saliva, urine and plasma. However, the full understanding of the drying process in biocolloids is far from being achieved and, notably, the impact of solute properties on the morphological characteristics of the evaporating droplets, such as colloid segregation, skin formation and crack pattern development, is still to be elucidated. For this purpose, the use of model colloidal solutions, whose rheological behavior is more easily deducible, could represent a significant boost. In this work, we compare the drying of droplets of whey proteins and casein micelles, the two main milk protein classes, to that of dispersions of silica particles and polymer-coated silica particles, respectively. The mechanical behavior of such biological colloids and model silica dispersions was investigated through the analysis of crack formation, and the measurements of their mechanical properties using indentation testing. The study reveals numerous analogies between dairy and the corresponding model systems, thus confirming the latter as a plausible powerful tool to highlight the signature of the matter at the molecular scale during the drying process

Similarity in the drying behavior between biological colloids and model colloidal dispersions . Première réunion plénière du GDR SLAMM (Solliciter LA Matière Molle)

Drying is ubiquitous in industry and our everyday life. It is a priori a complex process involving coupled vapor diffusion and liquid transport through a complex, multi-scale, soft or solid, porous structure. Despite this complexity, many recent researches now provide insight in, and rationalization of, the physical processes at work in drying of soils, building materials, colloids, gels, model porous systems, etc. The aim of this meeting, within the frame of the Chair Innovating solutions for sustainable housing (Saint-Gobain –Ecole des Ponts ), is to gather experts and review significant improvements in our understanding in this scientific field.

National audience; Hypothesis: The effective contribution of interfacial properties to the rheology of foams is a source of many open questions. Film dynamics during topological T1 changes in foams, essentially studied for low molecular weight surfactants, and scarcely for proteins, could connect interfacial properties to protein foam rheology. Experiments: We modified whey protein isolate (WPI), and its purified major protein b-lactoglobulin (b-lg) by powder pre-conditioning and dry-heating in order to obtain a broad variety of interfacial properties. We measured interfacial properties, film relaxation duration after a T1 event and bulk foam rheology. Findings: We found that, for b-lg, considered as a model protein, the higher the interfacial elastic modulus, the longer the duration of topological T1 changes and the greater the foam storage and loss moduli and the yield stress. However, in the case of the more complex WPI, these correlations were less clear. We propose that the presence in WPI of other proteins, lactose and minerals modify the impact of pre-conditioning and dry-heating on proteins and thereby, their behaviour at the interface and inside the liquid film.

The production of milk powders involves nowadays a significant portion of the dairy industry. Due to its rich composition in terms of proteins and macromolecules, shedding light on the mechanisms characterizing the evaporation of milk is a scientific challenge and an industrial need at the same time. In this study, we use a multi-scale approach to investigate the separate roles of the two major milk protein components (whey protein isolates and native micellar caseins) on the drying of droplets with different whey protein to casein ratio. The evolution of the desiccation phases and the morphology of the samples are observed coupling mass measurements, optical/confocal microscopy and ultrasounds. Our outcomes highlight how the physico-chemical properties at the molecular scale significantly affect dried particle formation and their final shape and mechanical behavior. We show that the sol-gel transition governs the development of the particle skin in case of single dairy protein solution, regardless of the type. The case of the whey protein / micellar caseins mixes is discussed in a second time.