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The growing consumption of fermented products has led to an increasing demand for lactic acid bacteria (LAB), especially for LAB tolerant to freezing/thawing conditions. Carnobacterium maltaromaticum is a psychrotrophic and freeze-thawing resistant lactic acid bacterium. The membrane is the primary site of damage during the cryo-preservation process and requires modulation to improve cryoresistance. However, knowledge about the membrane structure of this LAB genus is limited. We presented here the first study of the membrane lipid composition of C. maltaromaticum CNCM I-3298 including the polar heads and the fatty acid compositions of each lipid family (neutral lipids, glycolipids, phospholipids). The strain CNCM I-3298 is principally composed of glycolipids (32%) and phospholipids (55%). About 95% of glycolipids are dihexaosyldiglyceride while less than 5% are monohexaosyldiglyceride. The disaccharide chain of dihexaosyldiglyceride is composed of α-Gal(1-2)-α-Glc chain, evidenced for the first time in a LAB strain other than lactobacillus strains. Phosphatidylglycerol is the main phospholipid (94%). All polar lipids are exceptionally rich in C18:1 (from 70 to 80%). Regarding the fatty acid composition, C. maltaromaticum CNCM I-3298 is an atypical bacterium within the genus Carnobacterium due to its high C18:1 proportion but resemble the other Carnobacterium strains as they mostly do not contain cyclic fatty acids.

(1) Background: Adding white vinegar to the batter of a sponge cake without biological fermentation requires the effects of acidification on the batter to be checked, in particular concerning batter-to-crumb transition. (2) Methods: µDSC analyses were carried out on three batters formulated from flour, colza oil, salt, carrot, and water with or without the addition of white vinegar. (3) Results: Wheat, chickpea, and quinoa starches had gelatinization temperatures (TGe) of 60.1, 72.4, and 70.5 °C at batter humidity and gelatinization enthalpies (ΔHGe) of 9.2, 15, and 9.1 J/gdry starch. Due to the effect of the salt and carrot, the corresponding wholemeal batter had TGe of 64.2, 74.1, and 72.4 °C and ΔHGe of 10.5, 15.3, and 10.9 J/gdry starch. Acidified batters at pH 4 saw their TGe decrease, and their enthalpies increase compared to the controls. The calorimetric study of model mixtures revealed three different evolutions of ΔHGe as a function of pH, explained by the isoelectric behavior of flours and/or the attack of starch by acetic acid. (4) Conclusions: These results could be useful for adapting the cooking step of the acid batter in order to produce alternative snacks.

International audience; Aqueous extracts of Rhynchophorus phoenicis larvae were prepared at pHs 3.0 to 10.0 to screen their macronutrient composition, emulsifying properties and identify the best conditions to extract a functional protein ingredient. The results showed that the aqueous extracts contained both proteins (0.85 –4.62 mg/mL), characterized by a large range of molecular weights, and lipids (0.28 to 1.54 mg/mL). The lipids were composed mainly of triacylglycerols (0.21 to 0.95 mg/mL) and free fatty acids (FFA, 0.06 to 0.62 mg/mL) with the highest FFA levels at alkaline pHs; they contained 4.1 to 8.8 g polyunsaturated fatty acids per 100 g total fatty acids. The highest protein extraction yield (54%) of the insect proteins occurred at pH 9.0–10.0. Whatever the extracting pH, the aqueous extracts were able to stabilize oil-in-water emulsions. The emulsions prepared with the pH 9.0 and 10.0 aqueous extracts had however the lowest mean droplet size (d4.3 < 2 μm), and showed no creaming after storage at 4 °C for one weak, indicating that stable emulsions can be prepared at these pHs. Alkaline conditions of extraction will thus be suitable to prepare protein concentrate/isolate of R. phoenicis larvae and test their aptitude to be used to formulate new food products.

This work is part of a study aiming to design a high-throughput foaming microsystem. The main focused field of application is the food industry. With the objective of improving the design of the microdevice, the effects of the geometry and the nature of the liquid base are presently investigated through visualizations of the flow typology of bubbles trains, aiming to expand the knowledge on key parameters that lead to an improved gas breakup. The tested set of conditions is not encountered in traditional microfluidics systems: i.e., throughputs up to 19 L·h−1 for the liquid phase, process velocities around 20 m·s−1 and flow of complex fluids. The behavior of solutions based on xanthan gum (XG) and whey proteins (WPI) is compared to that of solutions containing one of these ingredients or other ones (caseinates, glycerol). The structural and end-used properties of the final foams, namely the bubble diameter and rheological behavior, are evaluated. The incorporation of XG induces bubble shape stabilization even at the highest shear rates (~105 s−1) encountered in the mixing channel. “Controlled” interfacial breakup by tip-streaming or binary breakup are only observed with the WPI/XG biopolymers. This study indubitably highlights the essential role of the process/formulation interaction in the development of structural and functional properties of food foams when using microfluidics at high throughput.

Acid milk gels with fat (3.5 or 10%) or without fat containing 0.2–1% of whey proteins (WP) or 0.2–1.5% of protein aggregates (fractal aggregates, microgels and mixed casein/WP aggregates with an 80/20 ratio) were investigated. The fat-containing systems were homogenized and the systems were preheated (90 °C, 11 min) and acidified to a pH of 4.6 by adding glucono-delta-lactone. The protein composition of the fat droplet interface was characterized by SDS-PAGE and the textural and rheological properties, microstructure, and whey separation of acid networks were determined. WP and fractal aggregates showed the best ability to improve the textural properties and microstructure of all acid milk gels and reduce whey separation. Increasing the concentrations in microgels and mixed aggregates did not lead to an increase in gel firmness or generate a strong impact on the protein network, but a high concentration in mixed aggregates could reduce whey separation. The fat droplet interface was made almost exclusively of caseins, even if the fractal aggregates could also be adsorbed when the interfacial surface was increased either through fat content or through an increase in homogenization pressure. Adding proteins changes the textural properties of the acid gels in all the systems, mainly due to their role in the continuous phase.

International audience; The use of plant proteins to design colloidal food systems is a hot topic in the current context of the protein transition. However, replacing animal-derived proteins (in particular, dairy proteins) that have been traditionally used for this purpose by plant proteins is a challenge from various perspectives, and in particular, because of drastically different solubility and functionality. A possible route to mitigate these issues is to combine plant and dairy proteins, providing that their interactions can be understood from the molecular to the macroscopic scale. This review addresses the major advances that have occurred in the field of such blend-based systems, all the way from their behaviour in aqueous dispersions to their potential applications in gels, foams and emulsions.

The viscosities of solutions formulated with xanthan gum and xanthan gum with whey protein isolates are experimentally characterized and modeled over a wide range of shear rates [10−3to 105s−1]. As shown by numerous studies [1, 2], the generation of vortices in the cone-plate geometry is making viscosity measurements beyond a certain shear rate unreliable. In the present work, an innovative technique, based on microfluidics and developed by the company Formulaction, has been employed to extend to high shear rates, the viscosity flow curve obtained with a rotational rheometer. The main highlights of this study are firstly, to propose a scaling law for the inertial transition in the cone-plate geometry for different diameters and angles through the determination of the maximum shear rate at which one can expect a true viscosity value. Secondly, the high shear rate measurements allow the determination of the second Newtonian plateau for these solutions thanks to the Williams-Carreau model. An attempt for the second plateau modeling is proposed following the concept of an intrinsic viscosity in the high shear equilibrium. In the same way, other fitted parameters from the Williams-Carreau law are modeled as a function of the polymer concentration. This procedure allows to provide a predictive model for the rheological behavior of xanthan gum-based solutions used in high shear processes like high pressure homogenization, emulsification, foaming, microfluidics, etc in food, pharmaceutical or cosmetics applications.

International audience; Proteins are widely used to stabilize emulsions, and plant proteins have raised increasing interest for this purpose. The interfacial and emulsifying properties of proteins depend largely on their molecular properties. We used fluorescence spectroscopy to characterize the conformation of food proteins from different biological origins (dairy or pea) and transformation processes (commercial or lab-made isolates) in solution and at the oil-water interface. The fourth derivative of fluorescence spectra provided insights in the local environment of tryptophan (Trp) residues and thus in the protein structure. In emulsions, whey proteins adsorbed with their Trp-rich region at the oil-water interface. Proteins in the commercial pea isolate were present as soluble aggregates, and no changes in the local environment of the Trp residues were detected upon emulsification, suggesting that these structures adsorb without conformational changes. The lab-purified pea proteins were less aggregated and a Trp-free region of the vicilin adsorbed at the oil-water interface.

International audience; Lutein is a xanthophyll carotenoid provided exclusively by the diet, that has protective functions and beneficial effects on human health. Supplementation in lutein is necessary to reach the recommended daily dietary intake. However, the introduction of lutein into foods and beverages is a real challenge since this lipophilic nutrient has a poor aqueous solubility and a low bioavailability. In this study, we investigated the capacity of egg-sphingomyelin (ESM) vesicles called sphingosomes to solubilise lutein into the bilayers. The thermal and structural properties of ESM bilayers were examined in presence of various amounts of lutein by differential scanning calorimetry (DSC) and temperature-controlled X-ray diffraction (XRD), the structures of sphingosomes and lutein crystals were observed by microscopic techniques. ESM bilayers were in the fluid L α phase above the phase transition temperature T m = 39.6 • C and in the lamellar ripple P β ′ phase below T m where ESM sphingo-somes exhibited ondulations and were facetted. Lutein molecules were successfully incorporated into the ESM bilayers where they induced a structural disorganisation. For ESM/lutein 90/10 %mol (91.8/8.2 %wt; 89 mg lutein / g ESM), lutein partitioning occured with the formation of lutein crystals in the aqueous phase together with lutein-loaded ESM vesicles. This study highlighted the capacity of new lipid carriers such as egg-sphingosomes to solubilise lutein and opens perspectives for the formulation of effective lutein-fortified func-tionnal foods and beverages providing health benefits.

The digestion of plant protein is highly dependent on multiple factors, with two of the most important being the protein source and the food matrix. The present study investigated the effects of these two factors on the digestion of seitan (a wheat-based food), tofu, soya juice, and a homemade emulsion of soy oil and water that was stabilised with pea protein. The four plant matrices and their respective protein isolates/concentrates (wheat gluten, soya protein, pea protein) were subjected to in vitro static digestion following the INFOGEST consensus protocol. We monitored the release of α-amino groups during digestion. We found that food matrix had a strong influence on protein digestion: soya juice was more hydrolysed than fresh tofu (51.1% versus 33.1%; P = 0.0087), but fresh tofu was more hydrolysed than soya protein isolate (33.1% versus 17.9%; P < 0.0001). Likewise, the pea-protein emulsion was better hydrolysed than the pea-protein isolate (P = 0.0033). Differences were also detected between the two solid foods investigated here: a higher degree of hydrolysis was found for tofu compared to seitan (33.1% versus 11.8%), which was perhaps a function of the presence of numerous dense protein aggregates in the latter but not the former. Furthermore, freeze-drying more than doubled the final degree of hydrolysis of seitan (P < 0.0001), but had no effect on tofu (P = 1.0000). Confocal microscopy revealed that protein networks in freeze-dried seitan were strongly altered with respect to the fresh product; instead, protein networks in freeze-dried and fresh tofu were largely similar. Finally, we found that the pro-tease:protein ratio had a strong effect on the kinetics of proteolysis: a 3.7-fold increase in the concentration of the soya protein isolate with respect to that of the soya juice decreased the final degree of hydrolysis from 50.3 to 17.9% (P = 0.0988).

The heat stability of whey protein emulsions remains a real challenge due to the rapid denaturation/aggregation of native whey proteins on heating. The use of heat-stable Pickering-like whey protein microgels (WPM) makes it possible to develop heat-stable emulsions in a large range of whey protein concentrations. In this study, emulsion heat stability was evaluated with a special focus on the contribution of WPM adsorbed at the fat droplet surface and in the continuous phase of the emulsion. Dairy emulsions were prepared with 30% milk fat and 70% suspension of WPM in the dispersed phase of milk. The protein interfacial load and the composition of the fat droplet surface were determined immediately after emulsion formation, and the heat stability of the emulsions at 120 °C was assessed visually and at microscopic scale. WPM are heat stable in the continuous phase of the emulsion, but the presence of WPM at the surface of the fat droplets is responsible for a rapid gelation of the emulsions. In the heated emulsions, the fat droplets seemed to be crosslinked by WPM. The presence of caseins instead of WPM at the fat droplet surface allowed the heat stability of the emulsion to recover at low and high whey protein concentrations. This study shows that it is possible to prepare heat-stable whey protein–rich emulsions by using whey proteins previously aggregated as heat-stable WPM and a sufficient amount of caseins in order to fully cover the fat droplet surface. These results will contribute to the development of heat-stable whey protein–rich emulsions.

International audience; This work is focused on the development of a compact continuous process for the production of food foams with controlled properties. Cross-shaped channels of infra millimeter size are used and the two-phase flow pattern is analyzed in order to identify the mechanisms of bubble deformation and breakup at very high velocities [similar to 2-20 m s(-1)]. Two different microcrochannel designs are used, differing by the presence of an abrupt expansion in one of the devices. Similar breakup mechanisms are observed in both devices in the cross-shaped channels and an additional local elongational flow was identified in the expansion. The expansion was found to intensify bubble breakup. All the experiments are carried out with the same gas content and the same liquid mix prepared from biosourced molecules (xanthan gum and whey proteins). A dimensional analysis is proposed in order to model the diameter of bubbles at the moment of their formation. (C) 2019 Elsevier Ltd. All rights reserved.

International audience; The context of this work is to explore the possibility of making bio-sourced foams at high throughput in microsystems. A fundamental element for the development of new technologies based on biphasic flows in microchannels is a good characterization and knowledge of hydrodynamics. In this contribution, cross slot microsystems are tested as a promoter for the formation of train of bubbles in aqueous solutions of xanthan gum. A flow chart is proposed to present the conditions allowing a dispersed flow regime; i.e. the conditions guaranteeing the complete incorporation of the gas into the liquid phase (no gas pocket) and then the control of the void fraction. The foaming is studied under potential industrial conditions, i.e. operating with liquid flow rates up to 24 L/h. High speed imaging within the channels reveals that the mechanism of formation of bubbles is related to flow focusing. Bubbles are generated alternatively from each of the two opposite gas inlets. Using whey protein isolate to enhance foaming points out that the bubble size may be reduced along a long channel by tip streaming. The effect of the modulation of the viscosity of the liquid base (xanthan gum content) is also discussed.

International audience; A computational fluid dynamics model was designed to study the problem of thermal processing of a liquid food product containing whey proteins within a heat exchanger consisting of heating, holding and cooling tubular sections. This physical problem is associated with strong coupling between the phenomena of fluid flow, heat transfer, and thermal denaturation-aggregation of whey proteins. Our primary objective was to investigate the two-way coupling between these phenomena within the heat exchanger. This was carried out by analyzing the model predictions of velocity, temperature and product properties at both axial and radial directions. Attention was focussed on the whey proteins present in a cream cheese formulation. The thermal denaturation-aggregation kinetics was supposed to follow that of the beta-lacto-globulin, which plays a major role in fouling when milk derivatives are submitted to thermal processing in heat exchangers. Model predictions demonstrated that the apparent viscosity of the liquid product exhibited a complex behavior along the processing unit: in addition to its dependence on local temperature, it was affected by the local degree of denaturation of whey proteins – and hence on the product history previous to this position in the heat exchanger. The numerical model was structured into a sequence of computational domains; its versatility was illustrated by changing the length of the holding section and then assessing the impact on the final degree of denaturation of the whey proteins present in the liquid product.

Whey protein microgels (WPM) are highly stable on heating and form Pickering-like emulsions exhibiting long-term resistance to coalescence. However, the heat stability of WPM emulsions is unclear and depends on the emulsion characteristics (WPM concentration, presence of non-microgel proteins such as caseins). The objective of this study was to investigate the heat-stability of WPM emulsions in the presence of caseins in order to clarify the role of the two types of proteins in the mechanism of heat-stabilization/destabilization. Emulsions (30 wt% milkfat) containing WPM (from 2.34 to 6.84 wt%) and non-microgel proteins, mainly caseins (from 0 to 0.81 wt%), were prepared at pH 7. A comparison of the emulsions before and after heating at 120 °C up to 30 min allowed their classification in three categories: viscous emulsions that gelled on heating (emulsions E1), fluid emulsions that gelled on heating (emulsions E2) and fluid emulsions even after heating (emulsion E3). A characterization of the fat droplet surface (protein interfacial load, protein composition, structure of the adsorbed entities by transmission electron microscopy) indicated emulsions E1 and E2 had WPM adsorbed at the fat droplet surface but their structural rearrangement did not explain the heat-induced modifications. Emulsions E3 had a fat droplet interfacial layer composed of caseins whereas the WPM were only located in the continuous phase. These results demonstrate that the WPM do not contribute to emulsion heat-stability but they do not induce heat instability as long as they are not situated at the fat droplet interface. Knowing the total interfacial area, the amount of caseins to obtain heat stable emulsions containing WPM can be evaluated because the caseins dominate WPM adsorption at the fat droplet surface. This knowledge will allow controlling the stability of dairy emulsions in a wider whey protein concentration range than when using native whey proteins.

The biological membrane surrounding fat globules in milk (milk fat globule membrane; MFGM) is an interface involved in many biological functions and interactions with the surrounding proteins or lipolytic enzymes in the gastro-intestinal tract during digestion. The MFGM exhibits lateral heterogeneities resulting from the different phase states and/or head-group charge of the polar lipids, which were both hypothesized to drive interaction with the casein micelles that is the major milk protein assembly. Atomic force microscopy (AFM) imaging was used to track the interactions of casein micelles with hydrated supported lipid bilayers of different composition, phase state and charge. Zeta-potential and Langmuir isotherms of the different polar lipids offered additional information necessary to interpret AFM observations. We showed that the negatively-charged casein micelles did not interact with milk sphingomyelin in the gel or liquid-ordered phases but did interact with polar lipids in the liquid-disordered phase (unsaturated polar lipids and milk sphingomyelin above its melting point). A wide intermolecular distance between polar lipids allowed protein adsorption on the membranes. However, the presence of the anionic polar lipids phosphatidylserine and phosphatidylinositol prevented any interaction with the casein micelles, probably due to electrostatic repulsion. These results open perspectives for the preparation of tailored emulsions covered by polar lipids able to modulate the interfacial interactions with proteins.

International audience; An artificial oil-in-water emulsion analogous to those found in bioresources or food matrices is simulated and studied experimentally. It is composed of one of the major natural free fatty acids (the oleic acid, OA) and the corresponding triacylglyceride (trioleic glyceride, or triolein, GTO). Because of the large time and length scales involved, the molecular simulations are done with the Martini force field, a coarse-grained model. This allowed us to study the water-OA-GTO system at different compositions with more than 20 000 molecules and up to 2 mu s. Interfacial tension was measured using the pendant drop method and compared with molecular simulation results. We observe very good agreement at high OA concentrations and deviations up to 15% at low OA concentrations. The water solubility in the lipid phase is in fair agreement with experiments, between 0.03 and 0.32 mol/l, rising with the OA content. The area occupied by OA and GTO at the interface between water and the pure product fitted with experimental data (A(OA) = 36.6 angstrom(2) and A(GTO) = 152.1 angstrom(2)). The consistency between simulation and experimental results allowed a structural analysis of the interface. A bilayer structure of the lipids at the water/oil interface is proposed, containing preferentially oleic acid but also triolein. Through all these results, the usefulness of coarse-grained simulation for the description of water-oil interfacial organization is demonstrated. This method will be used later to bring local information on the organization of target compounds, necessary in biomass fractionation processes or food additive formulations, for example. Published by AIP Publishing.

International audience; Environmental, demographic and economic motives draw a worldwide tendency to introduce plant proteins into processed foods. However the total replacement of animal proteins by plant proteins is not easy to perform due to the specific physicochemical properties (aggregation, solubility, interactions ...) and taste of these proteins. In a first step, combined plant/animal assemblies could be an attractive approach. Consequently, to drive this trend towards practical applications, deeper investigations must be performed to control the properties of such mixed assemblies. In the current study, the interactions of beta-casein with napin, a rapeseed protein poorly valorized in human nutrition, was investigated in various physico-chemical conditions (pH, sodium chloride concentration, mass ratio). The properties of the mix were followed by turbidimetry, and microscopy. The statistical analysis of the whole set of data indicated that the effects of the three factors were significant (p < 0.05) without significant cross effects. Furthermore, the aggregation is enhanced by temperature with a reversible effect. The aggregation is also suppressed by adding salt or divalent cation chelating agents (ethylene diamine tetracetic acid, EDTA). The functional combination of beta-casein with napin can thus be controlled by modulating the salinity of the media and/or by introducing a complexing agent.

Background:Human milk composition analysis seems essential to adapt human milk fortification for preterm neonates. The Miris human milk analyzer (HMA), based on mid-infrared methodology, is convenient for a unique determination of macronutrients. However, HMA measurements are not totally comparable with reference methods (RMs).Objective:The primary aim of this study was to compare HMA results with results from biochemical RMs for a large range of protein, fat, and carbohydrate contents and to establish a calibration adjustment.Methods:Human milk was fractionated in protein, fat, and skim milk by covering large ranges of protein (0-3 g/100 mL), fat (0-8 g/100 mL), and carbohydrate (5-8 g/100 mL). For each macronutrient, a calibration curve was plotted by linear regression using measurements obtained using HMA and RMs.Results:For fat, 53 measurements were performed, and the linear regression equation was HMA = 0.79RM + 0.28 ( R2= 0.92). For true protein (29 measurements), the linear regression equation was HMA = 0.9RM + 0.23 ( R2= 0.98). For carbohydrate (15 measurements), the linear regression equation was HMA = 0.59RM + 1.86 ( R2= 0.95). A homogenization step with a disruptor coupled to a sonication step was necessary to obtain better accuracy of the measurements. Good repeatability (coefficient of variation < 7%) and reproducibility (coefficient of variation < 17%) were obtained after calibration adjustment.Conclusion:New calibration curves were developed for the Miris HMA, allowing accurate measurements in large ranges of macronutrient content. This is necessary for reliable use of this device in individualizing nutrition for preterm newborns.

Protein fractions were extracted from pumpkin (Cucurbita maxima) seeds with deionized water, salt solution, and alkali solution, and characterized under alkaline (pH 8) and ionic strength conditions for protein solubility, interfacial pressure, and functional properties. The supernatants obtained from the protein fractions after hydration and centrifugation were designed deionized water supernatant, salt solution supernatant, and alkali solution supernatant. All protein fractions showed poor foamability and very low stability. The designed deionized water supernatant presented the highest emulsifying properties. In terms of stability, designed deionized water supernatant emulsions flocculate during storage but with low rates of coalescence compared to the two other fractions.

• Protein interactions play a key role in determining the final structure and properties of products.

During heat treatment, whey proteins (WP) are denatured and form different kinds of whey protein aggregates (WPA) depending on the physico-chemical conditions. In the presence of casein micelles, mixed aggregates (MA), resulting from the interaction of κ-casein and WP, are formed. The aim of this study is to understand the effect of pH on the WPA structure and the impact of the casein/whey proteins (Cas/WP) ratio on MA morphology. In this work, WP solutions were heated at pH 5.8 or 7 to produce WPA. On the other hand, aqueous mixtures containing three Cas/WP ratios (82/18, 56/44 and 30/70) were heated at 80 °C during 1 h at pH 6.3 to obtain MA. Milk protein aggregates were analyzed by Transmission Electron Microscopy (TEM) and Asymmetrical Flow Field-Flow Fractionation coupled with Multiangle Laser Light Scattering and Differential Refractometer (AF4-MALLS-DRi). Dense and spherical WPA were formed at pH 5.8 whereas branched and fractal aggregates were obtained at pH 7. Regarding MA, results suggested that they were mainly produced with the 82/18 Cas/WP ratio whereas a majority of WPA was obtained with the 30/70 ratio. At intermediate ratio, the mixture was composed of small MA and WPA that did not interact with κ-casein. Moreover, WP seem to interact preferentially with larger casein micelles. Thereby, AF4-MALLS-DRi proved to be a powerfull technique to characterize the complex structure of milk protein aggregates and an interesting alternative to size exclusion chromatography especially for MA and casein micelles which interact with the stationary phase and are retained in the column.

International audience; The objective of this work is to produce food foams in a continuous process while maintaining the required end-use properties of the foams such as stability and adequate texture.Foams are elaborated from liquid bases formulated with 3 wt% whey protein isolates as surfactant and xanthan gum (0.35–0.6 wt %) as thickener. A previous work with SMX™ 10 static mixer (Sulzer™) managed to produce foams with air fractions in the range [0.85–0.94], but the target range of the air fraction in food products is [0.5–0.8].This work aims at reducing bubbles size in the matrix in order to develop the interface and therefore to consolidate the structure. A static mixer of smaller size, the SMX+™ 6, is then used to increase the shear rate, and is compared to the SMX™ 10. The effect of the viscosity of the matrix is also investigated by using different formulations. The air fractions obtained are between 0.72 and 0.84, which is more relevant for food applications. The rheological analyses of foams are carried out by flow curves and viscoelasticity in the linear domain.It is shown that the foam shear viscosity ranks in the same order as the liquid base one, and that the yield stress and elastic modulus are in fair agreement with models of the literature.

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International audience; Native proteins usually undergo structural modification upon adsorption at interface. Heat treatments are commonly applied at the industrial scale and lead to aggregation of proteins. We characterized nanometric aggregates of beta-lactoglobulin by infrared spectroscopy in solutions, in hexadecane oil-in-water emulsions and at the air-water interface at low and high (0.1 M) ionic strengths and at pH 7. In solutions, on the contrary to native beta-lactoglobulin, all aggregates prepared with or without salt possessed intermolecular beta-sheets evidenced by two strong absorption bands at 1614 cm(-1) and 1682 cm(-1). In emulsions, at low ionic strength, they lose their intermolecular beta-sheets once they are adsorbed at the oil-water interface. At high ionic strength, most of aggregates are localized at the interfaces where they lose their intermolecular beta-sheets in direct contact with the surface and only partially when they are farther from the interface. The loss of intermolecular beta-sheets was similarly observed at the air-liquid interface. (c) 2013 Elsevier Ltd. All rights reserved.

International audience; Microchannels are used to produce food foams with the aim of obtaining void fractions and flow rates that are in accordance with food industry targets. Whey protein isolate is used as foaming agent and xanthan gum as thickening agent. At the high throughputs implemented, the shear thinning property of the fluid avoids excessive pressure drops. The tested microsystems allow mastering the foams structural properties, especially the bubble size. Stable foams are produced, even with void fraction of 0.55. Thanks to their particular structure, foams maintain their characteristics of rigidity at volume fractions lower than the maximum compactness. This outcome is also enhanced by the effect of salt on whey proteins interfacial film. The results are compared to data previously obtained with static mixers. Microchannels can be used as a continuous foaming process suitable for the food industry as well as a versatile tool for research and development in the scope of industrial expansion.

International audience; The homogenisation is an important operation in the dairy product processes, characterised by disruption of fat globules and then, coalescence between fat droplets and adsorption of milk proteins (monomers, polymers and aggregates of proteins) and other surfactants on fat droplet surface. Moreover, the homogenisation has often an impact on the textural properties of the products. In the literature, there are some articles dealing with the modelling of the phenomena occurring during the homogenisation. The aim of this work is to express some properties of the texture of the product from the structure. However, the models existing in the literature characterise the structure at a too fine scale to be linked to the texture. Consequently, we attempt to implement a mathematical model able to describe the interface of fat droplets during homogenisation at a mesoscopic scale involving texture. The approach consists in coupling models for the formation of the interface of fat droplets with an expert model to obtain the texture of the product, leading to an integrated knowledge model. This paper focuses on the model of formation of interface of fat droplets, using a mechanistic approach built from literature, expert knowledge and measurements and the qualitative is performed. Afterwards, an expert model, non deterministic, will be built with the output of the mechanistic model and the expert knowledge.

The influence of dynamically heat-induced aggregates on whey protein foams was investigated as a function of the thermal treatment applied to WPI using a bubbling technique. The aim was to determine the interplay between the size/shape/proportion of the heat-induced aggregates and the properties of protein foams (formation and stability). Results showed that insoluble protein aggregates were highly branched and cohesive, whereas soluble aggregates were constituted by subunits, associated by hydrophobic bonds and formed by α-La and β-Lg monomers linked by disulfide bridges. Using the bubbling procedure, protein aggregates were shown to slow down significantly foam formation. However, the rate of foam formation remained nearly unchanged for wet foams when the amount of insoluble aggregates was inferior to 5% and when their size remained lower than 100 μm. Similarly, protein aggregates did not seem to affect the destabilisation kinetics of wet foams, regardless of amount, size, shape and proportion.

International audience; Fat crystal networks confer their physical properties on fat-containing products. They are characterized by the solid fat content (SFC) and the design of the crystals, that is, their polymorphism and their size. Different techniques such as NMR,differential scanning calorimetry, and X-ray diffraction (XRD) are used to determine these parameters. Low-fieldNMR, the reference method for evaluation of SFC, has been proven to allow the determination of polymorphism through spin-lattice relaxation time (T1) and second moment (M2) measurements. However, this technique could provide more information on the system. On the basis of the effects of supercooling on theNMRparameters, the first evidence of a possible relationship between the size of the crystals and T1 was demonstrated. The effects of a liquid phase on the fat crystal network were investigated with liquid tricaprin and solid tristearin. It was demonstrated that the two triacylglycerols can cocrystallize, and that the liquid phase modified the polymorphic behavior of tristearin. The evolution of T1 over time could be related to the Ostwald ripening phenomenon. In view of this evidence, it was concluded that there was a relationship between T1 and the size of the crystals in the fat crystal network.

International audience; The 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.

International audience; The 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.

Heat treatments are used to extend the shelf life of manufactured food emulsions, which in turn requireexcellent heat stability. Whey protein aggregation prior to homogenization is a means to modifyemulsion heat stability but the underlying mechanism of heat stabilization has hardly been studied in anindustrial context where whey protein ingredients contain caseins. Emulsions were prepared with 30%anhydrous milk fat and 70% whey protein/casein solutions with protein concentrations ranging from 3 to6%. The proteins were either unheated (WP/Cas samples) or heat-aggregated (A-WP/Cas samples). Afterhomogenization, the fat droplet interface was characterized and emulsion stability was analyzed visuallyand at microscopic level. WP/Cas emulsions were heat stable at low protein concentrations but exhibiteda gradual decrease in heat stability when the protein concentration increased (>3%). This instability wasdue to the co-gelation of the protein-coated fat droplets and the proteins in the dispersing phase. Incontrast, A-WP/Cas emulsions were rapidly heat destabilized at low protein concentrations (

The chemical composition and crystallisation properties of milk fat and its primary fractions, obtained by dry fractionation at 21 degrees C, were investigated. The solid fraction (stearin) and the liquid fraction (olein) displayed a different triacylglycerol (TG) composition. Stearin fraction was enriched in long-chain fatty acids, whereas olein fraction was enriched in short-chain and unsaturated fatty acids. Crystallisation properties of milk fat, and both the stearin and olein fractions were studied on cooling at |dT/dt|=1 degrees C min(-1) by differential scanning calorimetry and time-resolved synchrotron X-ray diffraction (XRD) at small and wide angles. Two main types of crystals corresponding to double chain length structures were characterised in the stearin fraction: alpha 2L(1) (47.5 Angstrom) and beta' 2L(2) (41.7 Angstrom). A triple chain length structure was formed in the olein fraction: alpha 3L (72.1 Angstrom). Crystallization of milk fat showed the formation of two 2L (47.3 and 41.6 Angstrom) and one 3L (72.1 Angstrom) lamellar structures with an hexagonal packing (alpha form). A schematic representation of the 3L packing of olein fraction was proposed to explain how a wide diversity of TG can accommodate to form a lamellar structure with a thickness of 72 Angstrom. Furthermore, the sharpness of the small-angle XRD lines associated to the alpha form was explained by the formation of liquid crystals of smectic type.

The composition of goat milks originating from three animais homozygous for as! casein, variant A, and from three others, homozygous 0, was compared monthly over a lactation. Mean fat value was higher by 4.7 g kg:" in A milk, the difference between A and 0 reaching 9.8 g kg! in the early lactation. Total nitrogen matter was higher by 6.8 g kg-I in A milk on the whole lactation. Total casein levels in A and 0 milks were respectively 21.2 and 17.8 g kg :'. Caseins (CN) other than asl were at similar levels in the two groups of milks, aslCN was >- 5.2 g kg-I in A milk and - 0.0 g kg " in 0 milk. Mineral contents showed a high individual variability. Rennet coagulation tests led to higher firming rates and higher firmness in A milks, while coagulation time was not different between A and 0 milks. Total fatty acid proportions in milks were different: more short and medium length saturated fatty acids in A milk, balanced by a lower C 16 level. Lipolysis was by far lower in A milk and the relative proportion of fatty acids in the free fatty acid fraction was different in A and 0 milks, meaning a difference in lipase level and/or in lipase specificity due to the enzyme itself or to its environment. In contrast, pro- teolysis of the plasmin type was higher in A milks. © InralElsevier, Paris. goat milk / casein/Lj, variant / chemicaI composition / coagulation

National audience; Obtaining reliable in-silico food models is fundamental for a better understanding of these systems. The complex phenomena involved in these real-world processes reflect in the intricate structure of models, so that thoroughly exploring their behaviour and, for example, finding meaningful correlations between variables, become a relevant challenge for the experts. In this paper, we present a methodology based on visualisation and evolutionary computation to assist experts during model exploration. The proposed approach is tested on an established model of milk gel structures, and we show how experts are eventually able to find a correlation between two parameters, previously considered independent. Reverse-engineering the final outcome, the emergence of such a pattern is proved by physical laws underlying the oil-water interface colonisation. It is interesting to notice that, while the present work is focused on milk gel modelling, the proposed methodology can be straightforwardly generalised to other complex physical phenomena. Industrial relevance: Sustainability is nowadays at the heart of industrial requirements. The development of mathematical approaches should facilitate common approaches to risk/benefit assessment and nutritional quality in food research and industry. These models will enhance knowledge on process-structure-property relationships from the molecular to macroscopic level, and facilitate the creation of in-silico simulators with functional and nutritional properties. The stochastic optimisation techniques (evolutionary algorithms) employed in these works allow the users to thoroughly explore the systems: when coupled with visualisation, they make it possible to provide the experts with a restricted set of significant data, helping them to highlight eventual issues or possible improvements in the model. With regard to the complexity of the food systems and dynamics, the challenge of the mathematical approaches is to realise a complete dynamic description of food processing. In order to reach this objective, it is mandatory to use innovative strategies, exploiting the most recent advances in cognitive and complex system sciences. (C) 2014 Elsevier Ltd. All rights reserved.

Heat treatment applied to milk protein solutions can modify protein denaturation and aggregation state. Whey proteins (WP) are highly sensitive to heat treatment: above 70 degrees C they form aggregates or gels, while casein micelles (CM) are less affected but can complex with WP. Competitive adsorption during homogenization of milk protein stabilized emulsions leads to the formation of a heterogeneous complex layer at the interface. The aim of this study was to evaluate the effects of heat treatments (60 degrees C or 80 degrees C for 5 min) of different CM and WP aqueous mixtures (ratios from 80:20 to 12:88) on the structure of oil-water interface in relation to the texture of the emulsions. Different protein structures induced by heat treatment were characterised by light scattering and microscopy. Emulsion rheological properties were characterized and correlated with the amount of adsorbed protein, the composition and the structure of interface. Three kinds of rheological behavior and four different interfacial structures were characterized. In the first group, the emulsions were liquid, showing no connections between droplets. In the second group the emulsions were structured, the droplets being weakly connected by WP aggregated. In the third group the emulsions gelled, the droplets being connected by CM/WP complex or in other case by aggregated WP. The results are presented in a way that highlights the impact of the composition - structure relationship of the interface layer on the emulsion properties.

International audience; Previous studies have shown the feasibility of food foam production in a SMX10 static mixer. Nevertheless the void fraction, alpha, obtained was high (>0.85) compared to the target range in food industry (0.5-0.7). This work aims to reduce alpha by using a smaller hydraulic diameter of the static mixer (SMX+6) and higher liquid base viscosities. The hydrodynamic study exhibits slight differences in the pressure drop and process shear constants. The foams are processed with a liquid base of whey protein isolates (3%) and xanthan gum (0.35% or 0.6%). The boundaries between "slug flow" and "bubble flow" are determined for the two SMX and represented in a flow pattern map. Only the latter flow regime is suitable as alpha (0.73-0.96) can directly be controlled from the flow-rates. Working with a SMX+6 mm offers a substantial enlargement of the convenient velocity range that allows attaining lower void fractions compared to the SMX10.

Cream cheese is a good model for studying the effect of process and formulation changes on the modification of product texture. In this study, the intensity of heat treatment (72 degrees C/20 s or 94 degrees C/40 s), the final pH of acidification (pH 5.2 or 4.9) and the homogenization pressure (0, 5, 20, or 60 MPa) were studied. Special attention was paid to the whey protein denaturation, casein micelle dissociation, fat globule size and their relations with structural, rheological, and sensory characteristics of the cream cheese model. Rheological properties of final cream cheese mainly depended on homogenization pressure. Increasing the homogenization pressure led to a decrease in fat globule size and consequently in an increase in the cream cheese firmness. This result was modulated by heat treatment temperature and the subsequent whey protein denaturation. Cream cheese final pH between 5.2 and 4.9 had a low impact on rheological properties but was the most discriminating factor for sensory perception by strongly affecting product appearance especially its brightness and its shade.

National audience; Dairy products made of concentrated milk protein powder and milk fat have been experimentally shown to behave like complex systems: The resulting textures depend on various factors, including concentration and type of proteins, nature of heat treatment and homogenisation process. The aim of this paper is to combine two models in order to predict the composition of the interface of a homogenised oil-in-water emulsion, and the resulting bridge structure between the fat droplets. This structure is then correlated to the texture of the emulsion. Free unknown parameters of both models have been estimated from experimental data using an evolutionary optimisation algorithm. The resulting model fits the experimental data, and is coherent with the macroscopic texture measurements. Industrial relevance: Sustainability is nowadays at the heart of industrial requirements. The development of mathematical approaches should facilitate common approaches to risk/benefit assessment and nutritional quality in food research and industry. These models will enhance knowledge on process-structure-property relationships from molecular to macroscopic level, and facilitate creation of in-silico simulators with functional and nutritional properties. The stochastic optimisation techniques (evolutionary algorithms) employed in these works allow the users to thoroughly explore the systems and optimise it. With regard to the complexity of the food systems and dynamics, the challenge of the mathematical approaches is to realise a complete dynamic description of food processing. In order to reach this objective, it is mandatory to use innovative strategies, exploiting the most recent advances in cognitive and complex system sciences. (C) 2013 Elsevier Ltd. All rights reserved.

We report on the structure of whey protein aggregates formed by a short heating coupled to shear at high temperatures (80-120) and neutral pH in scale-up processing conditions, using gel filtration chromatography, light scattering, small angle neutron scattering, and cryogenic transmission electron microscopy. The results are interpreted in terms of coexistence of residual non-aggregated proteins and aggregates. The characteristics of aggregates such as the size, the aggregation number and the shape evidence two different morphologies. Whereas aggregates formed at 80 °C show a selfsimilar structure down to a length scale of the monomer with a fractal dimension typical for reaction limited cluster aggregation (D~2.2), aggregates formed at higher temperature show a spherical morphology, with the structure from small angle neutron scattering data best modelled with the form factor of a polydisperse sphere. We compare the structure of these aggregates to that of aggregates formed in quiescent conditions at lab scale. The structure transition is interpreted in terms of a non-trivial interplay between three perturbation factors: interparticle interaction, temperature and shear.

International audience; Fractal and spherical aggregates of whey globular proteins are formed under conditions that coupled heating and shear flow in a plate heat-exchanger at high temperature and for short holding time. Their properties upon adsorption and spreading at the air-water interface have been studied at neutral pH and two subphase conditions. The surface activity of mixtures of aggregates and residual proteins is enhanced and the adsorption behaviour depends strongly on the denatured native-like monomers and the charge screening. After long hours of adsorption, they form a weakly dissipative viscoelastic network, with strong interactions. When spread at the air-water interface, protein aggregates dissociate and form monolayers whose properties are described by scaling laws in the semi-dilute regime. The scaling exponents found in charge-screening subphase conditions correspond to values for polymer in theta-conditions, whereas the values determined in long-range repulsion subphase conditions are intermediate between an ideal (theta-conditions) chain and a chain in good solvent.

The optimization of the functionalities of commercial protein ingredients still constitutes a key objective of the food industry. Our aim was therefore to compare the effect of thermal treatments applied in typical industrial conditions on the foaming properties of whey protein isolate (WPI) and egg white proteins (EWP): EWP was pasteurized in dry state from 1 to 5 days and from 60 °C to 80 °C, while WPI was heat-treated between 80 °C and 100 °C under dynamic conditions using a tubular heat exchanger. Typical protein concentrations of the food industry were also used, 2% (w/v) WPI and 10% (w/v) EWP at pH 7, which provided solutions of similar viscosity. Consequently, WPI exhibited a higher foamability than EWP. For WPI, heat treatment induced a slight decrease of overrun when temperature was above 90 °C, i.e. when aggregation reduced too considerably the amount of monomers that played the key role on foam formation; conversely, it increased foamability for EWP due to the lower aggregation degree resulting from dry heating compared to heat-treated WPI solutions. As expected, thermal treatments improved significantly the stability of WPI and EWP foams, but stability always passed through a maximum as a function of the intensity of heat treatment. In both cases, optimum conditions for foam stability that did not impair foamability corresponded to about 20% soluble protein aggregates. A key discrepancy was finally that the dry heat treatment of EWP provided softer foams, despite more rigid than the WPI-based foams, whereas dynamically heat-treated WPI gave firmer foams than native proteins.

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.

International audience; We investigated the structure of heat-induced assemblies of whey globular proteins using small angle neutron scattering (SANS), static and dynamic light scattering (SLS and DLS), and cryogenic transmission electron microscopy (Cryo-TEM). Whey protein molecules self-assemble in fractal aggregates with a structure density depending on the electrostatic interactions. We determined the static and dynamic properties of interfacial layer formed by the protein assemblies, upon adsorption and spreading at the air-water interface using surface film balance and interfacial dilatational rheology. Upon spreading, all whey protein systems show a power-law scaling behavior of the surface pressure versus concentration in the semi-dilute surface concentration regime, with an exponent ranging from 5.5 to 9 depending on the electrostatic interactions and the aggregation state. The dilatational modulus derived from surface pressure isotherms shows a main peak at 6-8 mN/m, generally considered to be the onset of a conformational change in the monolayer, and a second peak or a shoulder at 15 mN/m. Long-time adsorption kinetics give similar results for both the native whey proteins and the corresponding self-similar assemblies, with a systematic effect of the ionic strength