International Journal of Agricultural and Environmental Information Systems
The scientific literature is a valuable source of information for developing predictive models to... more The scientific literature is a valuable source of information for developing predictive models to design decision support systems. However, scientific data are heterogeneously structured expressed using different vocabularies. This study developed a generic workflow that combines ontology, databases and computer calculation tools based on the theory of belief functions and Bayesian networks. The ontology paradigm is used to help integrate data from heterogeneous sources. Bayesian network is estimated using the integrated data taking into account their reliability. The proposed method is unique in the sense that it proposes an annotation and reasoning tool dedicated to systematic analysis of the literature, which takes into account expert knowledge of the domain at several levels: ontology definition, reliability criteria and dependence relations between variables in the BN. The workflow is assessed successfully by applying it to a complex food engineering process: skimmed milk micro...
National audienceThe expertise of both industry and research institutes has created an important ... more National audienceThe expertise of both industry and research institutes has created an important collection of knowledge on food processes, which is the result of scientific and technological research and experimental know- how. However, despite a great number of results published in the form of “peer” reviewed papers and patents, it has been failed to formalize, organize and complete the acquired knowledge. The need for a sustained capitalization is crucial in view of: i) preventing the loss of knowledge due to the departure of employees over the years; ii) avoiding the dispersal of existing experimental data; iii) and finally, allowing optimal exploitation of data and knowledge. The objective of this work is to address these challenges by developing an electronic knowledge book (kBook) of one specific food process, the microfiltration of skimmed milk. Microfiltration of skimmed milk is widely used in the dairy industry to separate casein micelles from soluble protein aiming at pro...
Ultra- and microfiltration of skim milk are widely used in the dairy industry for concentration a... more Ultra- and microfiltration of skim milk are widely used in the dairy industry for concentration and the fractionation of milk proteins. However their performances are limited by formation of a concentrated fouling layer of casein micelles at the membrane surface. Some precedent results on the possibly effect of operating conditions have been highlighted by Qu et al. (2012) and Jin et al. (2014). Nevertheless, there is a lack of knowledge on the behaviour of concentrated layer (sol-gel transition and reversibility) at different operating conditions. Consequently, the aim of this work is to elucidate the local structure and time dependant organization of casein micelles fouling layer under various operating conditions thanks to in-situ small-angle X-ray scattering SAXS during cross-flow ultrafiltration. This allowed to (i) distinguish the thickness and local solid concentration profiles in flowing (sol) and stagnant (gel) parts of the fouling layer; (ii) discriminate the effect of tim...
Deux applications au fractionnement des proteines natives du lait : Le phosphocaseinate natif et ... more Deux applications au fractionnement des proteines natives du lait : Le phosphocaseinate natif et les proteines marquees . Journee Thematique Plateforme LAIT
The interfacial properties of colloidal particles influence their interaction with each other and... more The interfacial properties of colloidal particles influence their interaction with each other and with their environment. This, in turn, governs the physical and functional characteristics of colloidal systems such as emulsions found in foods, drugs or cosmetics. Milk has been an important part of the human diet for thousands of years. It is a natural oil-in-water emulsion in which the lipids are dispersed as ~0.1-10 μm colloidal assemblies called the milk fat globules (MFG). MFG are composed of a core droplet of triacylglycerols (TAG) surrounded by a biological membrane. This membrane, mainly composed of polar lipids, cholesterol and glycoproteins, acts as the interface with the surrounding bulk of milk proteins (ie. casein micelles and whey proteins) or with enzymes of the gastrointestinal tract during digestion. The physicochemical properties of MFG and their membrane composition are altered by technological treatments during the manufacture of dairy products (Lopez et al., 2015,...
The formation of a deposit layer on membrane surfaces is an important problem, particularly in mi... more The formation of a deposit layer on membrane surfaces is an important problem, particularly in milk filtration. Properties of the deposit and efficiency of deposit removal can be studied using various indirect methods based mainly on average membrane resistance in deposit formation-deposit removal cycles, but their conclusions on deposit reversibility depend on conditions surrounding deposit analysis. Here we present a method for direct characterization of the reversibility of deposit compression via analysis of local solid concentration distribution during deposit formation at constant pressure and cross-flow velocity and deposit removal after pressure relaxation. Two models are proposed for deposit characterization: a model of crossflow filtration with deposit formation to characterize deposit compressibility-permeability from the data on concentration distribution at steady-state of deposit formation, and a model for evaluating deposit swelling kinetics from the data on steady-state compressibility-permeability. The method was applied here for analysis of the deposit formed on the surface of a polymeric ultrafiltration membrane during crossflow filtration of casein micelle suspensions at 25 • C. Local solid concentration distribution in the deposit and concentration polarization layer was probed in situ using small-angle X-ray scattering (SAXS). Experiments were performed in a special-purpose SAXS-filtration cell. It was demonstrated that casein micelle deposits obtained at 1.1 bar transmembrane pressure swell after pressure relaxation. However, swelling rate was significantly lower than that obtained by modeling using deposit compressibility-permeability obtained from the analysis of steady-state concentration distribution. We thus find evidence that casein micelle deposits produced during crossflow membrane filtration undergo compression that is partially irreversible.
A recent work revealed that egg white (EW) at 45 °C exhibits a powerful bactericidal activity aga... more A recent work revealed that egg white (EW) at 45 °C exhibits a powerful bactericidal activity against S. enterica serovar Enteritidis, which is surprisingly little affected by removal of the >10 kDa EW proteins. Here, we sought to identify the major EW factors responsible for this bactericidal activity by fractionating EW using ultrafiltration and nanofiltration, and by characterizing the physicochemical and antimicrobial properties of the resulting fractions. In particular, 22 peptides were identified by nano-LC/MS-MS and the bactericidal activities of representative peptides (with predicted antimicrobial activity) were further assessed. Two peptides (FVPPVQR and GDPSAWSWGAEAHS) were found to be bactericidal against S. enterica serovar Enteritidis at 45 °C when provided in an EW environment. Nevertheless, these peptides contribute only part of this bactericidal activity, suggesting other, yet to be determined, anti-microbial factors.
High circulating levels of ceramides (Cer) and sphingomyelins (SM) are associated with cardiometa... more High circulating levels of ceramides (Cer) and sphingomyelins (SM) are associated with cardiometabolic diseases. The consumption of whole fat dairy products, naturally containing such polar lipids (PL), is associated with health benefits, but the impact on sphingolipidome remains unknown. In a 4-week randomized controlled trial, 58 postmenopausal women daily consumed milk PL-enriched cream cheese (0, 3, or 5 g of milk PL). Postprandial metabolic explorations were performed before and after supplementation. Analyses included SM and Cer species in serum, chylomicrons, and feces. The ileal contents of 4 ileostomy patients were also explored after acute milk PL intake. Milk PL decreased serum atherogenic C24:1 Cer, C16:1 SM, and C18:1 SM species (P group < 0.05). Changes in serum C16+18 SM species were positively correlated with the reduction of cholesterol (r = 0.706), LDL-C (r = 0.666), and ApoB (r = 0.705) (P < 0.001). Milk PL decreased chylomicron content in total SM and C24:1 Cer (P group < 0.001), parallel to a marked increase in total Cer in feces (P group < 0.001). Milk PL modulated some specific SM and Cer species in both ileal efflux and feces, suggesting differential absorption and metabolization processes in the gut. Milk PL supplementation decreased atherogenic SM and Cer species associated with the improvement of cardiovascular risk markers. Our findings bring insights on sphingolipid metabolism in the gut, especially Cer, as signaling molecules potentially participating in the beneficial effects of milk PL.
The rheological properties and microstructure of dairy gels involve the connectivity between milk... more The rheological properties and microstructure of dairy gels involve the connectivity between milk fat globules (MFG) and casein micelles that is affected by technological processes such as milk homogenization and heat treatment. The underlying mechanisms require further quantification of the interactions at the nanoscale level to be fully understood and controlled. In this study, we examined the adhesion of homogenized MFG to milk proteins and evaluated the role of ultra-high temperature (UHT) heat treatment and pH. The combination of physico-chemical analysis, rheology and microscopy observations at different scale levels associated to atomic force microscopy (AFM) force spectroscopy were used. AFM experiments performed at the particle scale level showed that adhesion of individual homogenized MFG to milk proteins (1) is increased upon acidification at pH 4.5: 1.4 fold for unheated samples and 3.5 fold for UHT samples, and (2) is enhanced by about 1.7 fold at pH 4.5 after UHT heat treatment of milk, from 176 pN to 296 pN, thanks to highly-reactive heat-denatured whey proteins located at the surface of MFG and caseins. The increased inter-particle adhesion forces accounted for more connected structures and stiffer UHT milk acid gels, compared to unheated-milk gels. Using a multiscale approach, this study showed that heat treatment of milk markedly affected the interactions occurring at the particle's surface level with consequences on the bulk structural and rheological properties of acid gels. Such findings will be useful for manufacturers to modulate the texture of fermented dairy products through the tailoring of heat-induced complexation of proteins and the connectivity of homogenized MFG with the protein network. This work will also contribute in a better understanding of the impact of process-induced changes on the digestibility and metabolic fate of proteins and lipids.
Hypothesis: The effective contribution of interfacial properties to the rheology of foams is a so... more 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.
Bioactive lipids of the milk fat globule membrane become concentrated in two co-products of the b... more Bioactive lipids of the milk fat globule membrane become concentrated in two co-products of the butter industry, buttermilk and butterserum. Their lipid composition is detailed here with special emphasis on sphingolipid composition of nutritional interest, determined using GC, HPLC and tandem mass spectrometry. Butterserum was 2.5 times more concentrated in total fat than buttermilk, with 7.7 ± 1.5 vs 19.5 ± 2.9 wt% and even more concentrated in polar lipids, with 1.4 ± 0.2 vs 8.5 ± 1.1 wt%. Both ingredients constitute concentrated sources of sphingomyelin (3.4 -21 mg/g dry matter) and contained low amounts of bioactive ceramides in a ratio to sphingomyelin of 1: 5 mol% in buttermilk and 1: 10 mol% in butterserum. Compared to other natural lecithins, these two co-products are rich in long and saturated fatty acids (C22:0-C24:0), contain cholesterol and could have interesting applications in neonatal nutrition, but also as brain-protective, hepatoprotective and cholesterol lowering ingredients.
Abstract The actual impact of the somatic cells in the dairy technology is still ill-defined, bec... more Abstract The actual impact of the somatic cells in the dairy technology is still ill-defined, because the increase in milk somatic cell count, usually correlated with mastitis factors, impairs the raw milk composition, through mainly unwanted proteolysis and lipolysis. This study used microfiltration technologies for recovering high quantity of somatic cells and for clarifying their role in cheese quality. Three series of Swiss-type cheeses were manufactured by adding 0 (control), 4 × 105 and 9 × 105 somatic cells mL−1. These cells were traced for the first time during the cheese making process by using adapted flow cytometry and real-time quantitative PCR. Proteolysis and lipolysis indices were measured throughout ripening time. Only a weak increase in lipolysis (+28%) and proteolysis (+8%) was observed in the highest somatic cell count cheese, despite 73% of the cells trapped within the cheeses. Our approach gives a new view of somatic cell role in cheese milk alteration.
The processes developed to valorize buttermilks and butter serums generally start by a technologi... more The processes developed to valorize buttermilks and butter serums generally start by a technological step aiming at removing lipids by centrifugation. The efficiency of this skimming step has never been studied yet. The objective of this study was then to characterize the efficiency of the skimming of industrial buttermilk and butter serum and to determine its consequences on the lipid composition and microstructure of related products. This work clearly shows that the efficiency of the skimming step, operated both at pilot and industrial scales, is never complete and depends on the characteristics of the fluids to be treated. There exists a threshold of lipid content (7% total lipids in dry matter for buttermilk; 20% for butter serum) under which the skimming is not efficient. Above this threshold of lipid content, the skimming step removes all particles with a size larger than 1 μm (large fat globules, butter fines), but does not succeed in removing small size lipid fraction (fragments of membrane, lipid vesicles), which results in an increase in the polar lipids on total lipid ratio for both products (up to 20 ± 5% and 49 ± 6% for buttermilks and butter serums respectively). The difference of skimming efficiency, threshold values of skimming, and composition of final products between the buttermilks and butter serums could be attributed to differences in the microstructure of the lipids. Even if not totally efficient, the skimming step leads to a standardization of total lipid content of buttermilks and butter serums, useful for a better control of technological processes aiming at valorizing individual compounds of these dairy by-products.
Abstract Milk polar lipids (PLs) are poorly utilised as ingredients for human consumption, despit... more Abstract Milk polar lipids (PLs) are poorly utilised as ingredients for human consumption, despite their interesting nutritional and functional properties. The objective of this study was to valorise by-products by developing a technological process able to provide a milk PL-enriched ingredient from industrial fresh liquid butter serum. The process comprised the following successive steps: skimming, heat treatment, acid precipitation of caseins, concentration and purification of whey butter serum by ultrafiltration and diafiltration. The proposed process yields a recovery of 62% of PLs present in the initial butter serum. The final ingredient contained 31.5%, 26% and 34% of PLs, proteins and triacylglycerols (on a dry matter basis). The identified proteins were caseins, whey proteins and proteins from the milk fat globule membrane. This process will allow the preparation of a milk PL-rich ingredient for food applications.
This study deals with the precipitation of calcium phosphate in permeates removed from milks at d... more This study deals with the precipitation of calcium phosphate in permeates removed from milks at different pH (6.7, 5.2 and 4.6). An overall high yield of precipitation of calcium and phosphate (70-80%, respectively) was obtained for all precipitates with Ca ⁄ P molar ratios close to 1.5. The suspended milk-derived calcium phosphate (MDCP) precipitates had 8-14 lm size and )14 to )28 mV zeta potential. The dried MDCP precipitates were identified as amorphous calcium phosphate (ACP), stable over 18 months of storage at room temperature.
Crossflow microfiltration (0.1 m) of skimmed milk is widely used in the dairy industry to separat... more Crossflow microfiltration (0.1 m) of skimmed milk is widely used in the dairy industry to separate casein micelles from soluble proteins. The accumulated matter at the membrane surface turns into an irreversible deposit in critical hydrodynamic conditions (CHC) (J/τ w ) crit that irreversibly alters filtration performance. The aim of this work was to identify the milk constituents responsible for CHC and to evaluate the role of constituents (casein micelles, soluble proteins, minerals) on the microfiltration performance and deposit structure. An original methodology of filtration based on step-by-step τ w variation at constant flux was used with dairy fluids of variable and controlled composition. Casein micelles were shown to be the milk constituents responsible for the apparition of the CHC, creating an irreversible deposit at the membrane surface. Soluble proteins had no effect on the set-up of the CHC, but their presence in milk increased by 20% the irreversible fouling. The presence of the mineral aqueous phase of milk played a role in CHC set-up and irreversible fouling. Calcium ions are supposed to create bonds in the deposit between the membrane and the micelles and between micelles themselves.
The taste-active compounds of a Camembert cheese selected for its intense bitterness defect were ... more The taste-active compounds of a Camembert cheese selected for its intense bitterness defect were investigated. The water-soluble fraction (WSE) was extracted with pure water and fractionated by successive tangential ultrafiltrations and nanofiltration. The physicochemical assessment of these fractions led to the construction of a model WSE which was compared by sensory evaluation to the crude water-soluble extract, using a panel of 16 trained tasters. As no significant difference was perceived, this model WSE was then used directly or mixed with other cheese components for omission tests. Among the main taste characteristics of the WSE (salty, sour, umami and bitter), bitterness was found to be due to small peptides whose mass distribution was obtained by RPHPLC-MS (400–3000 Da) and whose taste properties are discussed.
International Journal of Agricultural and Environmental Information Systems
The scientific literature is a valuable source of information for developing predictive models to... more The scientific literature is a valuable source of information for developing predictive models to design decision support systems. However, scientific data are heterogeneously structured expressed using different vocabularies. This study developed a generic workflow that combines ontology, databases and computer calculation tools based on the theory of belief functions and Bayesian networks. The ontology paradigm is used to help integrate data from heterogeneous sources. Bayesian network is estimated using the integrated data taking into account their reliability. The proposed method is unique in the sense that it proposes an annotation and reasoning tool dedicated to systematic analysis of the literature, which takes into account expert knowledge of the domain at several levels: ontology definition, reliability criteria and dependence relations between variables in the BN. The workflow is assessed successfully by applying it to a complex food engineering process: skimmed milk micro...
National audienceThe expertise of both industry and research institutes has created an important ... more National audienceThe expertise of both industry and research institutes has created an important collection of knowledge on food processes, which is the result of scientific and technological research and experimental know- how. However, despite a great number of results published in the form of “peer” reviewed papers and patents, it has been failed to formalize, organize and complete the acquired knowledge. The need for a sustained capitalization is crucial in view of: i) preventing the loss of knowledge due to the departure of employees over the years; ii) avoiding the dispersal of existing experimental data; iii) and finally, allowing optimal exploitation of data and knowledge. The objective of this work is to address these challenges by developing an electronic knowledge book (kBook) of one specific food process, the microfiltration of skimmed milk. Microfiltration of skimmed milk is widely used in the dairy industry to separate casein micelles from soluble protein aiming at pro...
Ultra- and microfiltration of skim milk are widely used in the dairy industry for concentration a... more Ultra- and microfiltration of skim milk are widely used in the dairy industry for concentration and the fractionation of milk proteins. However their performances are limited by formation of a concentrated fouling layer of casein micelles at the membrane surface. Some precedent results on the possibly effect of operating conditions have been highlighted by Qu et al. (2012) and Jin et al. (2014). Nevertheless, there is a lack of knowledge on the behaviour of concentrated layer (sol-gel transition and reversibility) at different operating conditions. Consequently, the aim of this work is to elucidate the local structure and time dependant organization of casein micelles fouling layer under various operating conditions thanks to in-situ small-angle X-ray scattering SAXS during cross-flow ultrafiltration. This allowed to (i) distinguish the thickness and local solid concentration profiles in flowing (sol) and stagnant (gel) parts of the fouling layer; (ii) discriminate the effect of tim...
Deux applications au fractionnement des proteines natives du lait : Le phosphocaseinate natif et ... more Deux applications au fractionnement des proteines natives du lait : Le phosphocaseinate natif et les proteines marquees . Journee Thematique Plateforme LAIT
The interfacial properties of colloidal particles influence their interaction with each other and... more The interfacial properties of colloidal particles influence their interaction with each other and with their environment. This, in turn, governs the physical and functional characteristics of colloidal systems such as emulsions found in foods, drugs or cosmetics. Milk has been an important part of the human diet for thousands of years. It is a natural oil-in-water emulsion in which the lipids are dispersed as ~0.1-10 μm colloidal assemblies called the milk fat globules (MFG). MFG are composed of a core droplet of triacylglycerols (TAG) surrounded by a biological membrane. This membrane, mainly composed of polar lipids, cholesterol and glycoproteins, acts as the interface with the surrounding bulk of milk proteins (ie. casein micelles and whey proteins) or with enzymes of the gastrointestinal tract during digestion. The physicochemical properties of MFG and their membrane composition are altered by technological treatments during the manufacture of dairy products (Lopez et al., 2015,...
The formation of a deposit layer on membrane surfaces is an important problem, particularly in mi... more The formation of a deposit layer on membrane surfaces is an important problem, particularly in milk filtration. Properties of the deposit and efficiency of deposit removal can be studied using various indirect methods based mainly on average membrane resistance in deposit formation-deposit removal cycles, but their conclusions on deposit reversibility depend on conditions surrounding deposit analysis. Here we present a method for direct characterization of the reversibility of deposit compression via analysis of local solid concentration distribution during deposit formation at constant pressure and cross-flow velocity and deposit removal after pressure relaxation. Two models are proposed for deposit characterization: a model of crossflow filtration with deposit formation to characterize deposit compressibility-permeability from the data on concentration distribution at steady-state of deposit formation, and a model for evaluating deposit swelling kinetics from the data on steady-state compressibility-permeability. The method was applied here for analysis of the deposit formed on the surface of a polymeric ultrafiltration membrane during crossflow filtration of casein micelle suspensions at 25 • C. Local solid concentration distribution in the deposit and concentration polarization layer was probed in situ using small-angle X-ray scattering (SAXS). Experiments were performed in a special-purpose SAXS-filtration cell. It was demonstrated that casein micelle deposits obtained at 1.1 bar transmembrane pressure swell after pressure relaxation. However, swelling rate was significantly lower than that obtained by modeling using deposit compressibility-permeability obtained from the analysis of steady-state concentration distribution. We thus find evidence that casein micelle deposits produced during crossflow membrane filtration undergo compression that is partially irreversible.
A recent work revealed that egg white (EW) at 45 °C exhibits a powerful bactericidal activity aga... more A recent work revealed that egg white (EW) at 45 °C exhibits a powerful bactericidal activity against S. enterica serovar Enteritidis, which is surprisingly little affected by removal of the >10 kDa EW proteins. Here, we sought to identify the major EW factors responsible for this bactericidal activity by fractionating EW using ultrafiltration and nanofiltration, and by characterizing the physicochemical and antimicrobial properties of the resulting fractions. In particular, 22 peptides were identified by nano-LC/MS-MS and the bactericidal activities of representative peptides (with predicted antimicrobial activity) were further assessed. Two peptides (FVPPVQR and GDPSAWSWGAEAHS) were found to be bactericidal against S. enterica serovar Enteritidis at 45 °C when provided in an EW environment. Nevertheless, these peptides contribute only part of this bactericidal activity, suggesting other, yet to be determined, anti-microbial factors.
High circulating levels of ceramides (Cer) and sphingomyelins (SM) are associated with cardiometa... more High circulating levels of ceramides (Cer) and sphingomyelins (SM) are associated with cardiometabolic diseases. The consumption of whole fat dairy products, naturally containing such polar lipids (PL), is associated with health benefits, but the impact on sphingolipidome remains unknown. In a 4-week randomized controlled trial, 58 postmenopausal women daily consumed milk PL-enriched cream cheese (0, 3, or 5 g of milk PL). Postprandial metabolic explorations were performed before and after supplementation. Analyses included SM and Cer species in serum, chylomicrons, and feces. The ileal contents of 4 ileostomy patients were also explored after acute milk PL intake. Milk PL decreased serum atherogenic C24:1 Cer, C16:1 SM, and C18:1 SM species (P group < 0.05). Changes in serum C16+18 SM species were positively correlated with the reduction of cholesterol (r = 0.706), LDL-C (r = 0.666), and ApoB (r = 0.705) (P < 0.001). Milk PL decreased chylomicron content in total SM and C24:1 Cer (P group < 0.001), parallel to a marked increase in total Cer in feces (P group < 0.001). Milk PL modulated some specific SM and Cer species in both ileal efflux and feces, suggesting differential absorption and metabolization processes in the gut. Milk PL supplementation decreased atherogenic SM and Cer species associated with the improvement of cardiovascular risk markers. Our findings bring insights on sphingolipid metabolism in the gut, especially Cer, as signaling molecules potentially participating in the beneficial effects of milk PL.
The rheological properties and microstructure of dairy gels involve the connectivity between milk... more The rheological properties and microstructure of dairy gels involve the connectivity between milk fat globules (MFG) and casein micelles that is affected by technological processes such as milk homogenization and heat treatment. The underlying mechanisms require further quantification of the interactions at the nanoscale level to be fully understood and controlled. In this study, we examined the adhesion of homogenized MFG to milk proteins and evaluated the role of ultra-high temperature (UHT) heat treatment and pH. The combination of physico-chemical analysis, rheology and microscopy observations at different scale levels associated to atomic force microscopy (AFM) force spectroscopy were used. AFM experiments performed at the particle scale level showed that adhesion of individual homogenized MFG to milk proteins (1) is increased upon acidification at pH 4.5: 1.4 fold for unheated samples and 3.5 fold for UHT samples, and (2) is enhanced by about 1.7 fold at pH 4.5 after UHT heat treatment of milk, from 176 pN to 296 pN, thanks to highly-reactive heat-denatured whey proteins located at the surface of MFG and caseins. The increased inter-particle adhesion forces accounted for more connected structures and stiffer UHT milk acid gels, compared to unheated-milk gels. Using a multiscale approach, this study showed that heat treatment of milk markedly affected the interactions occurring at the particle's surface level with consequences on the bulk structural and rheological properties of acid gels. Such findings will be useful for manufacturers to modulate the texture of fermented dairy products through the tailoring of heat-induced complexation of proteins and the connectivity of homogenized MFG with the protein network. This work will also contribute in a better understanding of the impact of process-induced changes on the digestibility and metabolic fate of proteins and lipids.
Hypothesis: The effective contribution of interfacial properties to the rheology of foams is a so... more 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.
Bioactive lipids of the milk fat globule membrane become concentrated in two co-products of the b... more Bioactive lipids of the milk fat globule membrane become concentrated in two co-products of the butter industry, buttermilk and butterserum. Their lipid composition is detailed here with special emphasis on sphingolipid composition of nutritional interest, determined using GC, HPLC and tandem mass spectrometry. Butterserum was 2.5 times more concentrated in total fat than buttermilk, with 7.7 ± 1.5 vs 19.5 ± 2.9 wt% and even more concentrated in polar lipids, with 1.4 ± 0.2 vs 8.5 ± 1.1 wt%. Both ingredients constitute concentrated sources of sphingomyelin (3.4 -21 mg/g dry matter) and contained low amounts of bioactive ceramides in a ratio to sphingomyelin of 1: 5 mol% in buttermilk and 1: 10 mol% in butterserum. Compared to other natural lecithins, these two co-products are rich in long and saturated fatty acids (C22:0-C24:0), contain cholesterol and could have interesting applications in neonatal nutrition, but also as brain-protective, hepatoprotective and cholesterol lowering ingredients.
Abstract The actual impact of the somatic cells in the dairy technology is still ill-defined, bec... more Abstract The actual impact of the somatic cells in the dairy technology is still ill-defined, because the increase in milk somatic cell count, usually correlated with mastitis factors, impairs the raw milk composition, through mainly unwanted proteolysis and lipolysis. This study used microfiltration technologies for recovering high quantity of somatic cells and for clarifying their role in cheese quality. Three series of Swiss-type cheeses were manufactured by adding 0 (control), 4 × 105 and 9 × 105 somatic cells mL−1. These cells were traced for the first time during the cheese making process by using adapted flow cytometry and real-time quantitative PCR. Proteolysis and lipolysis indices were measured throughout ripening time. Only a weak increase in lipolysis (+28%) and proteolysis (+8%) was observed in the highest somatic cell count cheese, despite 73% of the cells trapped within the cheeses. Our approach gives a new view of somatic cell role in cheese milk alteration.
The processes developed to valorize buttermilks and butter serums generally start by a technologi... more The processes developed to valorize buttermilks and butter serums generally start by a technological step aiming at removing lipids by centrifugation. The efficiency of this skimming step has never been studied yet. The objective of this study was then to characterize the efficiency of the skimming of industrial buttermilk and butter serum and to determine its consequences on the lipid composition and microstructure of related products. This work clearly shows that the efficiency of the skimming step, operated both at pilot and industrial scales, is never complete and depends on the characteristics of the fluids to be treated. There exists a threshold of lipid content (7% total lipids in dry matter for buttermilk; 20% for butter serum) under which the skimming is not efficient. Above this threshold of lipid content, the skimming step removes all particles with a size larger than 1 μm (large fat globules, butter fines), but does not succeed in removing small size lipid fraction (fragments of membrane, lipid vesicles), which results in an increase in the polar lipids on total lipid ratio for both products (up to 20 ± 5% and 49 ± 6% for buttermilks and butter serums respectively). The difference of skimming efficiency, threshold values of skimming, and composition of final products between the buttermilks and butter serums could be attributed to differences in the microstructure of the lipids. Even if not totally efficient, the skimming step leads to a standardization of total lipid content of buttermilks and butter serums, useful for a better control of technological processes aiming at valorizing individual compounds of these dairy by-products.
Abstract Milk polar lipids (PLs) are poorly utilised as ingredients for human consumption, despit... more Abstract Milk polar lipids (PLs) are poorly utilised as ingredients for human consumption, despite their interesting nutritional and functional properties. The objective of this study was to valorise by-products by developing a technological process able to provide a milk PL-enriched ingredient from industrial fresh liquid butter serum. The process comprised the following successive steps: skimming, heat treatment, acid precipitation of caseins, concentration and purification of whey butter serum by ultrafiltration and diafiltration. The proposed process yields a recovery of 62% of PLs present in the initial butter serum. The final ingredient contained 31.5%, 26% and 34% of PLs, proteins and triacylglycerols (on a dry matter basis). The identified proteins were caseins, whey proteins and proteins from the milk fat globule membrane. This process will allow the preparation of a milk PL-rich ingredient for food applications.
This study deals with the precipitation of calcium phosphate in permeates removed from milks at d... more This study deals with the precipitation of calcium phosphate in permeates removed from milks at different pH (6.7, 5.2 and 4.6). An overall high yield of precipitation of calcium and phosphate (70-80%, respectively) was obtained for all precipitates with Ca ⁄ P molar ratios close to 1.5. The suspended milk-derived calcium phosphate (MDCP) precipitates had 8-14 lm size and )14 to )28 mV zeta potential. The dried MDCP precipitates were identified as amorphous calcium phosphate (ACP), stable over 18 months of storage at room temperature.
Crossflow microfiltration (0.1 m) of skimmed milk is widely used in the dairy industry to separat... more Crossflow microfiltration (0.1 m) of skimmed milk is widely used in the dairy industry to separate casein micelles from soluble proteins. The accumulated matter at the membrane surface turns into an irreversible deposit in critical hydrodynamic conditions (CHC) (J/τ w ) crit that irreversibly alters filtration performance. The aim of this work was to identify the milk constituents responsible for CHC and to evaluate the role of constituents (casein micelles, soluble proteins, minerals) on the microfiltration performance and deposit structure. An original methodology of filtration based on step-by-step τ w variation at constant flux was used with dairy fluids of variable and controlled composition. Casein micelles were shown to be the milk constituents responsible for the apparition of the CHC, creating an irreversible deposit at the membrane surface. Soluble proteins had no effect on the set-up of the CHC, but their presence in milk increased by 20% the irreversible fouling. The presence of the mineral aqueous phase of milk played a role in CHC set-up and irreversible fouling. Calcium ions are supposed to create bonds in the deposit between the membrane and the micelles and between micelles themselves.
The taste-active compounds of a Camembert cheese selected for its intense bitterness defect were ... more The taste-active compounds of a Camembert cheese selected for its intense bitterness defect were investigated. The water-soluble fraction (WSE) was extracted with pure water and fractionated by successive tangential ultrafiltrations and nanofiltration. The physicochemical assessment of these fractions led to the construction of a model WSE which was compared by sensory evaluation to the crude water-soluble extract, using a panel of 16 trained tasters. As no significant difference was perceived, this model WSE was then used directly or mixed with other cheese components for omission tests. Among the main taste characteristics of the WSE (salty, sour, umami and bitter), bitterness was found to be due to small peptides whose mass distribution was obtained by RPHPLC-MS (400–3000 Da) and whose taste properties are discussed.
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Papers by nadine leconte