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It has been said that ‘a revolution in cheesemaking as a result of ultrafiltration is coming soon’.1 This revolution has been in the making for the past 25 years and has encompassed not only ultrafiltration but, more recently, microfiltration as well. Indeed, more than 400 000 tonnes of cheese were made using ultrafiltration technology in 1989.2 The history of cheesemaking using membranes commenced in the late 1960s with the invention of the MMV process.3–5 This process, named after its inventors (Maubois, Macquot and Vassel) opened up new avenues for significant advances in cheesemaking, including improvements in plant efficiencies, increases in cheese yield, development of continuous process, and possibilities of creating new cheese varieties. As a result, numerous plants all over the world, but mainly Europe, now use this process to manufacture a wide range of cheeses.6

Protein content of any source is classically determined through the analysis of its nitrogen content done for more 100 years by the Kjeldahl method, and the obtained result is multiplied by a number named nitrogen conversion factor (NCF). The value of NCF is related to the amino acid composition of the protein source and to the eventual presence of side groups covalently bound to some amino acids of the protein chain. Consequently, the value of NCF cannot be identical for all sources of food proteins. The aim of this paper is to review the available knowledge on the two allowed protein sources for infant food formulas, milk and soybean, in order to bring the right scientific basis which should be used for the revision of both European legislation and Codex Standard for Infant Formulas.

Summary To obtain functional yeast with antioxidant ability for food industry, the antioxidant activity of intact cell and intracellular cell-free extract of Pichia fermentans BY5 and Issatchenkia orientalis BY10 was investigated. Both intact cell and extract of them demonstrated antioxidant activity ranged from 49% to 68%. The ability to scavenge 1, 1-diphenyl-2-picrylhydrazyl free radicals were 12–41%. Furthermore, the reducing activity, Fe2+-chelating ability, scavenging of reactive oxygen species of extracts illuminated these two isolates had excellent antioxidant ability. And then, the attenuated effect of cell-free extracts from these two strains was evaluated using 4-nitroquiunoline 1-oxide (4-NQO) as an inducing reagent. The results indicated that the addition of extraction inhibit the lipid peroxidation induced by 4-NQO, which mainly caused by the protective intracellular protein rather than the polysaccharides. Therefore, these two yeast strains have potential to be utilised for production of functional foods.

Eleven different species of yeasts isolated from raw milk, such as Issatchenkia orientalis, Pichia fermentans, Rhodotorula mucilaginosa and Yarrowia lipolytica were identified using an integrated approach, including phenotypic and genotypic methods and the API 20C A UX system. Eleven selected strains which tolerated low pH levels, gastric juice and bile salt were further analysed for the presence of functional traits useful for probiotic application as antioxidants. The ability to scavenge DPPH (2, 2-diphenyl-1-picrylhydrazyl) and inhibit linoleic acid peroxidation indicated that P fermentans BY5 and HJ15 may be promising candidate strains for use as probiotics with antioxidarat activity.

– The protein composition of 24 individual Maiwa yak milk samples that were collected in the Sichuan province of China was determined by reversed-phase high-performance liquid chromatography. Yak milk differed from cow milk by its high concentration of total proteins (46.2– 58.4 g·L−1), total casein (40.2 g·L−1 on average) and the proportion of individual caseins. The high content of β-casein (more than 45%) and consequently the lower proportion of αs-casein (about 40%) together with a small increase in κ-casein (15%) appear to make this milk more favorable for infant nutrition as used by the Tibetan nomads. Also, the whey proteins, β-lactoglobulin and serum albumin, showed similarities in centesimal composition with the homologous cow whey proteins. However, this initial study on yak milk proteins has highlighted the lack of knowledge in the literature and underlines that much research is required to optimize the utilization of all components of this milk for people living in extreme climatic environments.

To study the chemical properties, the initial recovery of milk components, oiling off, and the textural properties of the cheese during a 60-day refrigerated storage period, skim milk was microfiltered through a 1.4-μm ceramic membrane to remove bacteria, and then low-moisture Mozzarella cheese was manufactured from medium-concentration factor (CF) microfiltration (MF) (0.1 μm of pore size, CF = 2.3) retentate with added cream. The changes in expressible serum (ES) were also studied. Three cheese-making trials were conducted on Mozzarella cheese milk using two different methods: MF and control. Changes in the levels of proteolysis patterns were monitored using pH 4.6-soluble nitrogen (SN), initially higher for microfiltration Mozzarella cheese (MMC) because of the higher content of caseinomacropeptide, and 12% trichloroacetic acid TCA-SN, and using SDS-PAGE. The levels of the secondary proteolysis (12% TCA-SN) were significantly higher in control Mozzarella cheese (CMC). The CMC showed a greater release of free oil at the beginning of aging time but this release was always lower than that observed for MMC. The textural characteristics (hardness, springiness, and cohesiveness) of both cheeses have significant differences, highly correlated to proteolysis indicators, during the ripening time. It is suggested that the differences in composition, proteolysis, oiling off, and textural characteristics in both the cheese and the ES attributes arise mainly as a result of the double content of calcium salts in 0.1-μm MF cheese issued from milk enriched with 2.3 times casein content. Indeed, the high content in calcium salts is known to inhibit autolysis of mesophilic lactic starter by increasing the buffering capacity of cheese aqueous phase, and then causing a slowdown of proteolysis. It likely leads to a different structuration of fat in Mozzarella cheese causing higher oiling off. The results obtained in this study show the possibility of making Mozzarella cheese from milk that has 2.3 times more micellar casein (50 g·kg−1), and to obtain products similar to those obtained from usual milk, adjustment of calcium salt mineralization is required.

RESUME La complexite organisationnelle des composants du lait a permis, paradoxalement, une application privilegiee, a ce liquide, de nombre de procedes technologiques innovants tels que les technologies separatives a membrane. L’industrie laitiere est maintenant a meme de mettre a la disposition des consommateurs des produits classiques (laits liquides et fromages au lait cru) de haute securite hygienique, n’ayant subi que des traitements thermiques moderes voire nuls, traitements toujours dommageables tant pour les qualites organoleptiques que pour la bio-activite de nombre de molecules laitieres. La mise en commun des acquis cognitifs de la Recherche sur les proprietes physiques et physico-chimiques des composants proteiques du lait avec les potentialites nouvellement offertes par ces technologies, notamment la microfiltration sur membrane, a aussi permis de differencier la cinetique d’assimilabilite des deux grands groupes de proteines (concept des proteines lentes et rapides), de produire des nouveaux derives debacterises, hautement purifies (caseine micellaire native et isolats de proteines de lactoserum repondant tant a des besoins de nutrition (laits infantiles, regimes amaigrissants) qu’a des besoins de fonctionnalite technologique. La meme technologie a ete appliquee au colostrum dans le but de produire un « serocolostrum » sterile contenant des immunoglobulines, des facteurs de croissance et d’autres molecules biologiquement actifs. Combines avec d’autres technologies separatives, les procedes a membrane devraient permettre a breve echeance, les separations et purifications industrielles des proteines dites mineures du lait auxquelles il est attribue une activite essentielle dans la fixation du calcium par l’os ou encore le transport physiologique de nombreuses vitamines. Sur un autre plan, grâce a la maitrise acquise des reacteurs enzymatiques a membrane, des etudes cliniques ont pu etre mises en place avec la Recherche medicale pour demontrer l’activite physiologique de plusieurs peptides bioactifs tels que le-caseinomacropeptide inducteur de la secretion de CCK (cholecystokinine), le αS1CN (91-100) a activite de type benzodiazepine, le κCN (106-116) a activite anti thrombotique ou encore les phosphopeptides des caseines αS et β facilitant l’absorption du fer et probablement aussi celle du calcium.

– Cantal is the third French Protected Denomination of Origin cheese. The Cantal cheesemaking process is similar to Cheddar cheese. Both processes involve a milling and a dry salting step which results in a homogeneous salted curd. In order to determine the key parameters of the manufacturing process acting on the specific characteristics of this cheese variety, an extensive and kinetic study repeated three times was carried out at nine stages from the raw milk to 120 d ripened cheese. The microbial ecosystem was explored by numeration and by direct extraction of DNA and PCR-Temporal Temperature Gradient Electrophoresis. Lysis of the lactic acid bacteria was checked by quantification of the intracellular lactate dehydrogenase activity. Carbon sources changes, solubilisation of minerals, proteolysis, lipolysis, and formation of neutral volatile compounds were also assessed. Cheese microstructure modifications and bacterial localisation were determined by confocal scanning laser microscopy. The controlled manufacturing conditions and the use of a complex mixture of starters led to very similar ripened cheeses. The compositional attributes (in particular total solids, fat, nitrogen forms), the lipolysis (0.7 ± 0.2% fat) and proteolysis final extent (34.4 g·kg–1 free amino acids in juice) were similar as well as major neutral volatiles compounds (2-butanone, ethanol and 2-butanol). Nevertheless, lactose and citrate metabolisms differed between the three trials and some free amino acids (Arg, Pro, Ser, Cit, Homocys) concentrations varied drastically during the ripening time course. CLSM micrographs showed that fat globules were disrupted during pressing and bacteria were preferentially localised at the fat/protein interface. As the lactic starter species were the same in the three trials and predominant during the cheese manufacture, the observed differences could result of one or several of the followings: (i) the raw milk microflora which showed to be different leading to growth or metabolism activity of particular subdominant populations during the process and the ripening; (ii) the more or less early lysis of the lactic starters; (iii) the possible interactions between raw milk microflora and the added starters. This extensive characterization of Cantal cheese provides a strong basis for building a rational concept of the key steps in which either technological actions or complementary microbial inoculation could be done in order to limit day to day variations.; Le fromage de Cantal est, en tonnage, la 3ème Appellation d'Origine Contrôlée française. Son procédé de fabrication, similaire à celui du Cheddar, implique une étape de broyage et salage à sec, qui résulte en un caillé salé homogène. Afin de déterminer les paramètres clé du procédé de fabrication agissant sur les caractéristiques spécifiques de cette variété de fromage, une étude approfondie et cinétique avec trois répétitions a été menée à 9 stades, du lait cru au fromage affiné 120 jours. L'écosystème microbien a été exploré par énumération et par extraction directe de l'ADN et PCR-Temporal Temperature Gradient Electrophoresis. La lyse des bactéries lactiques a été appréhendée par mesure de l'activité de la lactate déshydrogénase intracellulaire. Les changements intervenant dans les sources carbonées, la solubilisation des minéraux, la protéolyse, la lipolyse et l'apparition des composés volatiles neutres ont aussi été évalués. Les modifications de la microstructure du fromage ainsi que la localisation des bactéries ont été déterminées pas microscopie confocale à balayage laser (CLSM). La mise en oeuvre de conditions de fabrication très contrôlées et l'utilisation d'un levain complexe a conduit à des fromages affinés très similaires, tant sur le plan de la composition (en particulier l'extrait sec total, la matière grasse, les formes azotées) des niveaux de lipolyse (0.7 ± 0.2 % de la matière grasse) et de protéolyse (34,4 g·kg-1 d'acides aminés libres dans le jus) que sur le plan des teneurs en composés volatiles majoritaires (2-butanone, éthanol et 2-butanol). Néanmoins, les métabolismes du lactose et du citrate différaient entre les trois essais, ainsi que les concentrations en certains acides aminés libres (Arg, Pro, Ser, Cit, Homocys) qui variaient fortement au cours de l'affinage. Les photographies obtenues par CLSM montraient que les globules gras étaient brisés lors du pressage et que les bactéries étaient préférentiellement localisées à l'interface matière grasse/protéine. Comme le levain utilisé comportaient les mêmes espèces pour les trois essais et que celles-ci s'avéraient dominantes au cours de la fabrication, les différences observées peuvent résulter : (i) des variations observées dans la flore indigène du lait cru conduisant à la croissance ou l'activité métabolique de populations sous-dominantes particulières pendant la fabrication ou l'affinage ; (ii) de la lyse plus ou moins précoce des espèces du levain ; (iii) des interactions possibles entre la flore indigène du lait cru et le levain ajouté. Cette caractérisation approfondie du fromage Cantal offre une base solide pour construire un concept rationnel des étapes-clé au cours desquelles soit des actions technologiques, soit une inoculation microbienne complémentaire peuvent être réalisées afin de limiter les variations journalières et d'optimiser la qualité globale.

Treatment of bovine, equine and caprine colostrum by membrane microfiltration with a pore size of 0.1 µm was studied in order to obtain a specific separation of whey colostrum components. These components are most interesting for imparting passive immunity and positive physiological action to newborn mammals. From the carrying out of 80 kg batches of colostrum, the microfiltra- tion equipment used allowed the recovery of at least 80% of the IgG and other minor whey proteins in the microfiltrate. This liquid, named serocolostrum, is crystal clear, free of blood and somatic cells as well as fat globules and casein micelles, and it has a high hygienic and bacteriological qua- lity (less than 10 CFU·mL -1 ). Specific concentration of the serocolostrum IgG proteins by high molecular weight cut-off (MWCO: 100 kg·mol -1 ) membrane ultrafiltration was also studied in order to obtain purified IgG products suitable for preliminary animal trials. Purity (IgG/TS) as high as 90% was obtained. The use of a lower MWCO UF membrane (8 kg·mol-1) allowed concentra- tions of growth factors (TGF-β and IGF-1) but the observed separation did not agree with the data of the literature, i.e. a binding of IGF-1 with a 45 kg·mol -1 protein.

UF-cheeses have been successfully developed in many countries. However, proteolysis and the general extent of ripening were shown to be far slower compared to traditional varieties. The absence of starter lysis has been cited as a plausible explanation. In this work, propionibacteria and lactococci cells were disrupted using a new pilot homogenizer. Crude broken suspension (CBS), or cell-free extract (CFE), obtained after centrifugation, were added to UF-St Paulin retentate (concen- tration factor 6) made with a usual lactic starter. RO water was added to the control. Proteolysis was estimated by NCN, NPN and free amino acids. Neutral volatile compounds were determined by GC- MS. A low extent of ripening was noted in the control and the absence of starter lysis was effectively proved using immunodetection of lactococci cytoplasmic proteins. The addition of lactococci CBS or CFE increased free amino acid content (1.5 to 3 times) whereas propionibacteria CBS or CFE exhibited no significant increase, even when cheeses were ripened at 20 o C instead of 12 o C. By con- trast, addition of propionibacteria CBS generated a significant increase in several volatile compounds like alcohols and ketones, whereas CFE did not, showing that the presence of live cells was required to form these compounds. CBS or CFE of lactococci did not significantly change the volatile com- pound profile. In conclusion, it was possible to influence the ripening of UF-cheese by the addition of crude broken bacterial cell suspensions. Other strains and species should now be investigated. ultrafiltration / UF-cheese / GC-MS profile / broken cells / ripening / proteolysis / Lactococcus / propionibacteria

This paper deals with the most recent developments of cross flow microfiltration (CFMF), some of them just patented, in the dairy industry. Combination of the use of uniform trans- membrane hydraulic pressure concept (UTP) with its different ways of carrying out microfiltrate recirculation, longitudinal porosity gradient and of new ceramic membrane materials allows nowa- days to get a differential separation of each category of milk particles. Pretreatment by CFMF of incoming milk is used for the production of low heated fluid milks having a flavor similar to that of raw milk and a shelf life 3 to 5 times longer than that of classical products. Results observed in the retention by the MF membrane of pathogenic bacterial species allow it to be said that the hygienic safety of cheeses made from raw MF milk is, at least, equal or even higher than that of cheeses made from pasteurized milk. Numerous other applications of CFMF are under development such as removal of residual fat from whey or the clarification and the removal of bacteria from cheese brine but the most promising are undoubtedly the differential separation of micellar casein and of small milk fat globules. With the products obtained on both sides of the MF membrane, dairy technology will have the possibility not only to improve yield and quality of many dairy products but also to create a diversified range of new textures. microfiltration / membrane / liquid milk / native casein / brine / whey / cheese

International audience; The kinetics of whey drainage of Camembert soft cheese was studied using an instrumented drainage device to record the pH and the weight of the whey with a variation coefficient amounting to 1.8% during the first 100 min and 0.34% at the end of drainage. Drainage data were fit with a two step equation to obtain a descriptive model of the drainage kinetics. The effect of the pH at renneting, the casein concentration and the ionic strength on the drainage kinetics was investigated with a 2 level experimental design. Milk was modified by a combination of ultrafiltration and dilution with a lactose solution. The pH at renneting had a negative effect on the amount of whey expelled in the early drainage (up to 100 min) and a positive one after 400 min. The effect of the casein concentration was negative on the amount of whey expelled and on the rate of drainage. The ionic strength had a slight positive effect on drainage. An equation was obtained allowing the prevision of whey drainage kinetics according to the milk composition. Calculated values fit experimental data with a correlation coefficient of $r = 0.994$.; Caractérisation des cinétiques d'égouttage au cours de la fabrication d'un fromage type pâte molle en relation avec les facteurs physico-chimiques et technologiques : effet du pH d'emprésurage, de la teneur en caséine et de la force ionique des laits. L'égouttage du fromage à pâte molle de type Camembert a été étudié à l'aide d'un prototype d'égouttage instrumenté qui permettait d'enregistrer le poids de sérum et son pH. Le coefficient de variation était de 1,8 % pendant les 100 premières minutes et de 0,34 % à la fin de l'égouttage. Les cinétiques d'égouttage obtenues ont été ajustées à l'aide d'un modèle mathématique descriptif à deux phases. L'effet sur l'égouttage du pH à l'emprésurage et de modifications de la composition du lait, telle la concentration en caséine et la force ionique, ont été testés à l'aide d'un plan d'expérience à deux niveaux. La composition des laits était modifiée en combinant une concentration par ultrafiltration et une dilution par une solution de lactose. L'effet du pH sur le poids de sérum expulsé était négatif au début de l'égouttage puis devenait positif. L'effet de la concentration en caséine était négatif sur la quantité de sérum obtenue et sur la vitesse d'égouttage. La force ionique avait un léger effet positif sur l'égouttage. Une équation a été obtenue permettant de prévoir la cinétique d'égouttage en fonction de la valeur des trois facteurs étudiés. Les valeurs calculées s'ajustaient aux valeurs expérimentales avec un coefficient de corrélation $r=0,994$.

Caseins bind strongly to Fe by their phosphoseryl residues (Hegenauer et al. 1979; Brulé & Fauquant, 1982; Bouhallab et al. 1991; Emery, 1992) and keep it soluble at the alkaline pH of the duodenum (Manson & Annan, 1971; Bouhallab et al. 1991). It has been suggested that this strong binding prevents the release of free Fe during digestion and impairs its absorption (West, 1986; Hurrell, 1997), but in human studies hydrolysis by digestive enzymes to give low molecular mass peptides improves Fe absorption (Hurrell et al. 1988, 1989).β-Casein peptide 1–25 (β-CN(1–25)) is the phosphorylated N-terminal fragment of β-CN. Its molecular mass is 3124 Da and it contains four phosphoseryl residues that bind four Fe atoms and keep them soluble (Bouhallab et al. 1991).Preliminary results showed that binding Fe to β-CN(1–25) enhances its bioavailability in the rat (Aît-Oukhatar et al. 1997) and its absorption by the duodenal rat loop model (Pérès et al. 1997). We recently showed that the β- CN(1–25)–Fe complex is hydrolysed to a lesser extent than free β-CN(1–25) during duodenal digestion, and that the phosphorylated region of the peptide to which Fe is bound, β-CN(15–24), cannot be detected in the digestive lumen (our unpublished results).These previous studies did not examine the effect of luminal digestion that could release free inorganic Fe. We considered the possibility that Fe bound to β-CN(1–25) is not released in the digestive lumen, and that it reaches the absorbing surface of the small intestine brush border membrane as a complex. To test this hypothesis we examined in vitro the influence of pH and digestive enzymes on the dialysability of the β-CN(1–25)–Fe complex.

Partial removal of whey protein before heat-treatment, by a combination of membrane microfiltration and ultrafiltration according to an Inra patented process, was expected to avoid the for- mation of the β-lactoglobulin-κ-casein complex during thermal processing and thus to allow the production of a milk powder with cheesemaking abilities similar to those of raw milk. The prin- ciples of the process, the characteristics of the resulting new milk powder, and the manufacture of Moz- zarella cheese from milk prepared by recombination of this powder were studied with special empha- sis on rennet coagulability, melting properties and improvements observed on cheese yielding capacity. Mozarella produced by recombination had same composition and properties as control Mozarella (produced with raw fresh milk), but when the powder was used, the cheesemaking yields were 7.3 ∠ 1.8% higher in comparison with the control cheese. The recovery in total solids, fat and total nitrogen contents showed similar trends. Therefore, such a process may give rise to a new gene- ration of milk powders, especially suitable for cheesemaking in countries suffering a shortage in milk supply.

Binding iron to the phosphorylated beta(1-25) peptide derived from beta-casein improves iron bioavailability in the rat. The aim of the present work was to learn how injected beta(1-25) and iron-beta(1-25) complex behave in the duodenum of rats using the technique of intestinal ligation in situ and reversed-phase (RP)-high performance liquid chromatography-electrospray mass spectrometry analysis of the lumen contents. The results demonstrate that beta(1-25) is sensitive to digestive enzymes including proteases/peptidases and phosphatases during duodenal transit. The lumen contents of rats perfused with iron free beta(1-25) contained all peptidic sequences derived from beta(1-25). In contrast, the phosphorylated part of beta(1-25) [i.e., beta(15-24)] was not detected in lumen of rats perfused with iron-beta(1-25) complex.

We used the isolated, perfused rat duodenal loop system to assess the influence of binding iron (Fe) to soluble 1–25 caseinophosphopeptide (β-CN (1–25)), produced by the hydrolysis of β casein, against the inhibition of its absorption by Zinc (Zn). Fe (100 μM) was perfused as Fe gluconate (Fe Gluc) or bound to the β-CN (1–25) (Fe CN), alone (controls) or in presence of Zn as Zn sulfate (Zn SO4) or as (Zn CN) at Fe:Zn ratios ranging from 2:1 to 1:5. Zn SO4 reduced significantly disappearance from the lumen (Q1) and net Fe absorption (FeAbs) at Fe:Zn ratios from 1:1.5 to 1:5 (p

Bovine beta-lactoglobulin (beta-LG) is a widely studied protein belonging to the lipocalin family, whose structural characterisation has been reported by X-ray crystallography and NMR studies at physiological and acidic pH, respectively. Bovine beta-LG consists of nine antiparallel beta-sheets and a terminal alpha-helix segment. The beta-sheets form a calyx structure with a hydrophobic buried cluster conferring stability to the protein while a hydrophobic surface patch provides stabilising interactions between the barrel and the flanking terminal helix. Here, the stability and the folding properties of bovine beta-LG in the presence of a chemical denaturant is probed. The analysis of the NMR spectra recorded in aqueous solution with increasing amounts of urea revealed that the intensities of the backbone cross-peaks decrease upon increasing urea concentration, while their secondary shifts do not change significantly on going from 0 to 5 M urea, thus suggesting the presence of slow exchange between native and unfolded protein. Hydrogen exchange measurements at different urea concentrations were performed in order to evaluate the exchange rates of individual backbone amide protons. The opening reactions that determine protein exchange can be computed for the most slowly exchanging hydrogen atoms, and the measured exchange rates and the corresponding free energies can be expressed in terms of the equilibrium energetic for the global transition and the local fluctuations. Most of the residues converge to define a common isotherm identifying a unique cooperative folding unit, encompassing all the strands, except strand betaI, and the terminal region of the helix. The amides that do not join the same global unfolding isotherm are characterised by low DeltaGH20op and especially by low m values, indicating that they are already substantially exposed in the native state. A two-state unfolding model N U is therefore proposed for this rather big protein, in agreement with CD data. Renaturation studies show that the unfolding mechanism is reversible up to 6 M urea and suggest a similar unfolding and refolding pathway. Present results are discussed in light of the hypothesis of an alpha-->beta transition proposed for bovine beta-LG refolding.

y Since temperature and water activity are among the most important parameters that affect the Maillard reaction, the glycation sites in pure, native bovine β-lactoglobulin were determined after a mild heat treatment (60°C) in an aqueous solution and after a treatment under a restricted water environment (50°C, 65% relative humidity). In both systems, the results obtained underlined the structural heterogeneity of β-lactoglobulin (β-LG) glycoforms with respect to the number of lactose residues linked per protein molecule and to the binding sites involved. Subsequently, the effect of the glycation conditions on both the association behaviour and the conformational changes of the glycated β-LG were characterised by proteolytic susceptibility, binding of the fluorescent probe 8-anilino-1-naphtalene-sulfonic acid, SDS-PAGE and size exclusion chromatography. The results showed that dry-way glycation did not significantly alter the native-like behaviour of the protein while the treatment in solution led to important structural changes. These changes resulted in a specific denatured β-LG monomer, which covalently associated via the free thiol group. The homodimers thus formed and the expanded monomers underwent subsequent aggregation to form high molecular weight species, via non-covalent interactions. The use of monoclonal antibodies with defined epitopes, raised against native β-LG. confirmed that the protein conformation was much more modified when glycation was performed in a solution while the structural changes induced during dry-way treatment were limited to the AB loop region of the protein.

Direct monitoring of the Amadori product formation between lactose and β-lactoglobulin was performed by electrospray ionisation mass spectrometry. As expected, the glycation reaction was faster at low water activity than in aqueous system. Heterogeneous β-lactoglobulin glycoforms were observed, with different number of lactose bound: populations of β-lactoglobulin with 1 to 7 and 2 to 11 linked lactose were detected, respectively, after 10 and 22 h of reaction under 65% relative humidity and 50°C. Trypsinolysis of glycated proteins, followed by reverse-phase HPLC coupled to tandem mass spectrometry in the neutral loss scanning mode, indicated that all potential reactive amino groups, except Lys101, were involved in sugar binding. The resulting order of reactivity, as a function of reaction time, was as follows: Lys47,91>α-amino-group, Lys15,70,100>Lys60,69,75,77,83,135,138>Lys8,141.

The speed of absorption of dietary amino acids by the gut varies according to the type of ingested dietary protein. This could affect postprandial protein synthesis, breakdown, and deposition. To test this hypothesis, two intrinsically 13 C-leucine-labeled milk proteins, casein (CAS) and whey protein (WP), of different physicochemical properties were ingested as one single meal by healthy adults. Postprandial whole body leucine kinetics were assessed by using a dual tracer methodology. WP induced a dramatic but short increase of plasma amino acids. CAS induced a prolonged plateau of moderate hyperaminoacidemia, probably because of a slow gastric emptying. Whole body protein breakdown was inhibited by 34% after CAS ingestion but not after WP ingestion. Postprandial protein synthesis was stimulated by 68% with the WP meal and to a lesser extent (+31%) with the CAS meal. Postprandial whole body leucine oxidation over 7 h was lower with CAS (272 ± 91 μmol⋅kg −1 ) than with WP (373 ± 56 μmol⋅kg −1 ). Leucine intake was identical in both meals (380 μmol⋅kg −1 ). Therefore, net leucine balance over the 7 h after the meal was more positive with CAS than with WP ( P < 0.05, WP vs. CAS). In conclusion, the speed of protein digestion and amino acid absorption from the gut has a major effect on whole body protein anabolism after one single meal. By analogy with carbohydrate metabolism, slow and fast proteins modulate the postprandial metabolic response, a concept to be applied to wasting situations.

Iron forms strong and soluble complexes with 1–25 caseinophosphopeptide (CPP) issued from the enzymatic hydrolysis of β- casein . That could prevent iron from insolubilization and low digestive absorption. Young iron deficient rats (5 mg iron/kg diet for 4 weeks) were repleted (200 mg iron/kg diet, 2 weeks) using either FeSO 4 or iron bound to CPP of whole hydrolyzed β- casein (β- cas hydr group) or purified molecule (β- cas (1–25) group). Two other groups were fed a control diet (200 mg/kg as FeSO 4 ) for the 6 weeks, either and libitum (control) or pair fed (PF) to experimental groups. A metabolic balance was performed during the 2nd week of repletion. Experimental groups displayed a higher iron absorption than control groups, but did not differ among themselves. At the end of the 2 weeks repletion period, FeSO 4 and β- cas hydr groups showed similar values of Hb, Hct, and RBC count, which were lower than control and PF groups. Hct and Hb values of the β- cas (1–25) group were higher than β- cas hydr and FeSO 4 groups, but did not differ from control and PF animals. MCV values of control and PF groups did not differ from FeSO 4 group but were lower than the β- cas (1–25) and β- cas hydr groups. The Fe liver content was significantly higher in peptide-bound Fe groups ((1–25) β- cas and β- cas hydr) than the three other groups; the FeSO 4 group showed the lowest levels. Binding iron to phosphocaseinophosphopeptide seems to improve its bioavailability and to hasten the cure of iron deficiency in the young animal.

The influence of selected yeast strains (Pichia fermentans, Issatchenkia orientalis, Yarrowia lipolytica) on Camembert-type cheeses has been investigated by monitoring their microbial and compositional changes. During the ripening period from day 1 to day 15, the yeast strains grew exponentially and then slowed to a moderate growth rate. Our results indicated that the selected strains did not significantly affect the general characteristics of cheese but rather the content and ratio of individual free amino acids (P

L’Anses met en oeuvre une expertise scientifique indépendante et pluraliste.L’Anses contribue principalement à assurer la sécurité sanitaire dans les domaines de l’environnement, dutravail et de l’alimentation et à évaluer les risques sanitaires qu’ils peuvent comporter.Elle contribue également à assurer d’une part la protection de la santé et du bien-être des animaux et de lasanté des végétaux et d’autre part l’évaluation des propriétés nutritionnelles des aliments.Elle fournit aux autorités compétentes toutes les informations sur ces risques ainsi que l’expertise et l’appuiscientifique technique nécessaires à l’élaboration des dispositions législatives et réglementaires et à la mise enoeuvre des mesures de gestion du risque (article L.1313-1 du code de la santé publique).Ses avis sont rendus publics.L’Agence française de sécurité sanitaire des aliments1 (Afssa) a été saisie le 18 septembre 2009par l’association de consommateurs « Familles de France » d’une demande d’évaluation desrisques liés à la « présence de facteurs de croissance cancérigènes dans les produits laitiers ».1. CONTEXTE ET OBJET DE LA SAISINEL’association justifie sa demande par le fait qu’un nombre croissant de sites internet et d’ouvragessoutiennent la thèse selon laquelle des facteurs de croissance contenus dans le lait et les produitslaitiers consommés pourraient accroître le risque de cancers. A l’appui de ses interrogations,l’association souligne que de nouveaux traitements contre le cancer utilisent des « anti-facteurs decroissance ». L’association a ainsi saisi l’agence afin de connaître les concentrations des principauxfacteurs de croissance dans le lait et les produits laitiers actuellement proposés à la consommationet les dangers potentiels liés de ce fait à la consommation des produits laitiers.2. ORGANISATION DE L’EXPERTISEL’expertise a été réalisée dans le respect de la norme NF X 50-110 « Qualité en expertise –Prescriptions générales de compétence pour une expertise (Mai 2003) ».L’expertise relève du domaine de compétences du comité d’experts spécialisé (CES) « Nutritionhumaine ». L’Anses a confié l’expertise au groupe de travail (GT) « Facteurs de croissance, cancer,lait et produits laitiers ». Les travaux ont été régulièrement présentés au CES, tant sur les aspectsméthodologiques que scientifiques, entre novembre 2010 et décembre 2011. Ils ont été adoptés parun comité de validation désigné au sein du CES entre janvier et mars 2012. La procédure devalidation détaillée est présentée dans le rapport du groupe de travail.

The objective of this work was to characterize the fat globule and milk fat globule membrane (MFGM) proteins in Maiwa (n = 6), Gannan (n = 4) and Zhongdian yak whole milks (n = 4). Fat globule size distribution and specific fat surface area of whole yak milk were determined using a laser diffraction particle size analyzer. The average specific fat surface area of Gannan yak milk (2.05 m2·mg−1) and Zhongdian yak milk (2.01 m2·mg−1) was higher (P < 0.05) than that of Maiwa yak milk (1.92 m2·mg−1). The total protein content of MFGM and surface protein coverage of fat globule in Maiwa yak milk (11.12 mg·g−1 fat and 5.67 mg·m−2, respectively) and Gannan yak milk (12.24 mg·g−1 fat and 5.97 mg·m−2, respectively) were higher (P < 0.05) than that of Zhongdian yak milk (9.72 mg·g−1 fat and 4.81 mg·m−2, respectively). Protein components in the MFGM of yak milk were analyzed using an Ultrascan XL laser densitometer and an LKB 2400 GelScanXL software program. No major differences (P > 0.05%) in the protein patterns on the SDS gel were observed among the MFGM of Maiwa yak, Gannan yak and Zhongdian yak, with the exception of mucin 1 and butyrophilin which were significantly lower (P < 0.05) in the MFGM of Zhongdian yak milk.

– Consumption of dairy products containing probiotics with cholesterol-lowering activity has been proposed as a means to lower serum cholesterol. In the present work, 19 yeast strains, isolated from raw milk, were tested to obtain potential probiotic yeasts for assimilating cholesterol. During in vitro tests, 17 yeast strains were capable of growth in bile salt solutions, and most of the yeast strains tolerated low pH, surviving in gastric juice. Among the 19 strains assessed, Geotrichum sp. BY2 and Pichia kudriavzevii BY10 showed highest adhesive ability to HT-29 cells. All yeast strains were able to assimilate cholesterol in the range of 3.6–44.4% over a 72 h incubation, and seven of the yeast strains were significantly higher at assimilating cholesterol (P < 0.05). According to these results, the yeast strains P. fermentans BY5, P. kudriavzevii BY10, P. kudriavzevii BY15 and Yarrowia lipolytica HY4 may serve as potential probiotics to assimilate cholesterol in the human intestine.

The complex composition of milk has led to the development of innovative technological processes such as membrane separation. The dairy industry is now able to offer consumers safe classical products (liquid milk, raw-milk cheeses) with little or no heat treatment. Indeed, heat treatment undermines the organoleptic qualities and bioactivity of many molecules found in milk. New technologies, and especially membrane microfiltration, have allowed researchers to identify two groups of milk proteins in terms of their human absorption kinetics: slow micellar casein and fast whey proteins. The highly purified products thus obtained are used for infant foods and slimming aids, and as functional ingredients. The same technologies have been applied to colostrum, yielding a sterile "serocolostrum" containing biologically active immunoglobulins, growth factors, and polypeptides. Combined with other separation techniques, membrane technologies should soon allow the separation and purification of minor milk proteins described as having essential roles in bone calcium uptake and vitamin transport, for example. The use of enzymatic membrane reactors has led to the identification of several bioactive peptides, such as--kappa-caseinomacropeptide, which induces CCK (cholecystokinin) secretion and thus regulates food intake and lipid assimilation,--alpha(S1) CN (91-100), a compound with benzodiazepine activity,-- kappaCN (106-116), which has anti-thrombotic activity by inhibiting blood platelet binding to fibrinogen, and--alpha(S) and beta casein phosphopeptides, which are thought to increase iron and calcium absorption.

Indigenous yeasts can be detected at high populations in raw milk Cantal cheese, a French Protected Denomination of Origin (PDO) hard cheese. To investigate their use as adjunct cultures to promote flavour development in Cantalet (small Cantal) cheese, three strains isolated from raw milk Cantal cheese, Kluyveromyces lactis, Yarrowia lipolytica, and Pichia fermentans were added at 3 (E3) and 5 (E5) log(10) colony-forming units (cfu)/mL to microfiltered milk at a ratio of 80/10/10 viable cells, respectively. The global microbial, compositional and biochemical changes induced by the presence of yeasts in cheese were determined. Adjunct yeasts did not grow but stayed at viable populations of approximately 4 and 6 log(10) cfu/g in E3 and E5 cheeses, respectively, throughout the ripening period. They were mainly constituted of K. lactis, while P. fermentans and Y. lipolytica were not detectable after 3 and 45 days of ripening, respectively. Several species of indigenous yeasts were also detected in E3 cheeses at the beginning of ripening only, and in the control cheeses without yeasts added. Lactoccoci survived for longer periods in the presence of yeast adjuncts, while, conversely, the viability of Streptococcus thermophilus decreased more rapidly. The addition of yeasts did not influence cheese composition and total free amino acid content. In contrast, it slightly increased lipolysis in both E3 and E5 cheeses and markedly enhanced the formation of some volatile aroma compounds. The concentrations of ethanol, ethyl esters and some branched-chain alcohols were 6 to 10 fold higher in E5 cheeses than in the control cheeses, and only slightly higher in E3 cheeses. This study shows that K. lactis has a potential as cheese adjunct culture in Cantalet cheese and that, added at populations of 4-5 log(10) cfu/g cheese, it enhances the formation of flavour compounds.

International audience; Abstract – EGF, BTC, IGF-I, IGF-II, TGF-β1, TGF-β2, FGF1 and 2, and PDGF are the main growth factors present in bovine milk and colostrum. All of these growth factors are also found in human milk but at a lower concentration. The various compositional data reported in the literature vary greatly but it is evidenced that the day of lactation has the most important effect. Milk growth factors are characterized by a neutral to alkaline isoelectric point (pI) and a molecular mass between 6400 g·mol–1 and 30000 g·mol–1. However, many of the growth factors are in a latent form, bound to high-molecular-mass proteins. Milk growth factors are resistant generally to pasteurization but disulfide reducing agents have been found to inactivate some species such as TGF-β’s. The published data on bioavailability of milk growth factors are somewhat contradictory but it is generally accepted that they are resistant to gastric digestion and they can exert local and systemic effects on the gastrointestinal tract. Cation-exchange chromatography has been widely used for the extraction of milk growth factors because of the basic nature of these molecules. Membrane separations such as microfiltration (MF) have also been used successfully for the extraction of immunoglobulins and of some growth factors from colostrum, while ultrafiltration (UF) was successful only at separating IGF-I and IGF-II in whey. Milk growth factor extracts have been developed for various applications such as treatment of gastrointestinal disorders and skin diseases, wound healing, and induction of oral tolerance.; Les principaux facteurs de croissance retrouvés dans le lait bovin et le colostrum sont : EGF, BTC, IGF-I, IGF-II, TGF-b1, TGF-b2, FGF1 et 2, ainsi que PDGF. Les concentrations de ces facteurs de croissance dans le lait bovin sont supérieures à celles rapportées pour le lait humain. Les teneurs en facteurs de croissance retrouvées dans la littérature varient selon les auteurs mais il se dégage malgré tout que le jour de la collecte de l'échantillon au cours de la période de lactation représente le facteur de variation le plus important. Les facteurs de croissance du lait se caractérisent par un point isoélectrique (pI) alcalin et une masse moléculaire se situant entre 6400 g·mol-1 et 30 000 g·mol-1. Plusieurs des facteurs de croissance sont cependant présents dans le lait sous forme latente, souvent liés à des protéines de masses moléculaires élevées. Les facteurs de croissance du lait sont résistants à la pasteurisation alors que certains d'entre eux, comme les TGF-b's, peuvent être inactivés par des substances réductrices des ponts disulfures. Des données parfois contradictoires ont été publiées au sujet de la biodisponibilité des facteurs de croissance, mais il est généralement accepté que les facteurs de croissance résistent à la digestion gastrique et peuvent exercer des effets locaux et systémiques au niveau du tractus gastrointestinal. La chromatographie d'échange cationique a été largement utilisée pour l'extraction des facteurs de croissance, et ce, en raison de leur nature cationique. Les séparations membranaires comme la microfiltration (MF) ont été utilisées avec succès pour séparer des immunoblobulines et quelques facteurs de croissance du colostrum. L'ultrafiltration (UF) n'a été utilisée avec succès que dans la séparation de l'IGF-I et IGF-II présents dans le lactosérum. Des extraits de facteurs de croissance ont été développés pour diverses applications telles le traitement de désordres gastrointestinaux et de maladies de la peau, la cicatrisation et l'induction de la tolérance orale.

On behalf of the editorial board and the publishing staff of our international journal, it is my pleasure to inform our esteemed readers that from this issue, all published papers will have a summary in Chinese. Such a decision was taken in light of the impressive development of Chinese milk production and dairying (yearly growth rate higher than 35%), a development which requires giving to interested Chinese parties up-to-date information in the field, as will also be done by the next session of the IDF world congress in Shanghai. Our decision is also based on our certainty that Chinese Dairy R&D will rapidly become a major actor in the progress of knowledge related to this marvellous liquid "milk" and in its numerous derivatives, because of the hugeness and the variety of its needs in terms of scientific disciplines (biochemistry, microbiology, physico-chemistry, nutrition, etc.) and technology. Translations into the Chinese language will be undertaken by Professor Ying Ma, a very well-known Chinese dairy expert from the Harbin Institute of Technology, one of the most prestigious Chinese universities, to which the Chinese government has entrusted the responsibility of leading Chinese dairy science within its Graduate School of Food Science and Genetic Engineering. Consequently, in anticipation of the proceeding future top-level manuscripts from Chinese institutions, Professor Ying Ma has also been appointed deputy editor-in-chief for Asia.

Enrichment in micellar casein of bovine milk for making Kashkaval cheese was studied in order to face yearly variations in the composition of collected milk. Increase in casein content from 22.90 ± 0.01 g*kg-1 to 26.10 ± 0.02 g*kg-1 did not request change in the process parameters and led to cheeses with typical texture and an increase in the recovery of fat and casein in the cheese due to the acceleration of the organisation of the rennet curd matrix and a greater final firmness. The cheese yield was increased by 16.9%. On the other hand, increase in casein content to 29.20 ± 0.02 g*kg-1 led to a high increase in the vat acidification and to an unsatisfactory cheddaring step, which consequently involved protein losses in the draining whey., Fabrication de Kashkaval à partir de lait enrichi en caséine micellaire. La transformation de laits de vache enrichis en caséine micellaire en fromage Kashkaval a été étudiée dans le but d'utiliser cette standardisation pour pallier les variations annuelles de composition des laits collectés. L'accroissement de la teneur en caséine de 22,90 ± 0,01 g*kg-1 à 26,10 ± 0,02 g*kg-1 ne requiert aucune modification du procédé de fabrication et conduit à des fromages de texture typique et à une rétention accrue de la matière grasse et de la caséine dans le fromage en raison d'une cinétique d'organisation accélérée et d'une fermeté finale supérieure du coagulum présure. L'augmentation du rendement en fromage déterminée était de 16,9 %. Par contre, l'accroissement de la teneur en caséine à 29,20 ± 0,02 g*kg-1, en raison de l'élévation du pouvoir tampon du caillé, entraînait un allongement de son acidification et ne permettait pas une " cheddardisation " satisfaisante, ce qui conduisait à des pertes en protéines dans le lactosérum d'égouttage.

In spite of its high production (18000 T yearly), very few studies have been devoted to Cantal, a French AOC ("Appellation d'Origine Contrôlée") cheese variety whose making process is close to that of Cheddar. To improve the knowledge of this type of cheese, two ripened Cantal cheeses issued from raw milk and two different industrial processes were biochemically, physicochemically, structurally and microbiologically characterised through the analysis of both cheese sectors and juices extracted by pressure. The results obtained were compared with Cheddar and Emmental cheeses. The main differences between Cheddar and Cantal cheeses of the same age were a higher rate of proteolysis for Cantal cheese shown by both the total nitrogen content and the TCA soluble nitrogen in the respective cheese juices, and higher CaT content as well as an increased molar CaT/PT ratio in the Cantal cheese. Free amino contents in the cheese aqueous phase were similar but individual variations suggested an effect of the secondary ripening microflora provided by the raw milk used. Microbial counts done on different media showed a dominant mesophilic and thermophilic lactic acid bacteria flora, a subdominant flora composed of various ripening bacteria and yeasts and a very low level of some coliforms and of Pseudomonas. An amount of 44 neutral volatile compounds were identified but 3 of them determined by GC-MS (ethanol, 2-butanone and 2-butanol) represented more than 95% of the total peak area. Some variations in these main compounds as well as in minor ones confirmed a difference in the native microflora in the two studied Cantal cheeses. Nevertheless, these data appeared in the range of those reported for Cheddar. The microstructure of fat determined by confocal laser scanning micrography showed that little is present in Cantal cheese as intact fat globules. Most of this component appeared as free fat included in the casein matrix with a high ability to oil off, especially the part which is near the crust. As well as offering a precise characterisation of many compositional aspects of ripened Cantal cheese, this study opens the way for further works on the process kinetics carried out in the making processes and for a better knowledge of the ecosystem metabolism., Microstructure, physico-chimie, flore microbienne et composés aromatiques du fromage de Cantal affiné. En dépit de sa production élevée (18 000 T/an), peu d'études ont été consacrées au Cantal (3e Appellation d'Origine Contrôlée française) dont le procédé de fabrication peut être rapproché de celui du Cheddar. Pour accroître les connaissances sur cette variété de fromage, deux fromages Cantal affinés, obtenus à partir de lait cru, selon deux procédés de fabrication ont été caractérisés analytiquement au plan biochimique, physico-chimique, microbiologique et microstructural, à la fois par l'analyse des fromages et de leurs jus respectifs obtenus par extraction sous pression. Les résultats obtenus ont été comparés aux données existantes sur le Cheddar et l'Emmental. Les principales différences mises en évidence entre Cantal et Cheddar concernent le niveau de protéolyse (teneurs en N × 6,38 et proportion de N soluble dans le TCA accrues par rapport aux jus extraits de Cheddar), une teneur en CaT ainsi qu'un rapport molaire CaT/PT plus élevés dans le Cantal. Si la teneur en acides aminés libres ne différait globalement pas de celle décrite pour le Cheddar, les variations déterminées au niveau individuel suggéraient que l'activité métabolique de la microflore d'affinage (probablement apportée par le lait cru mis en œuvre) était différente entre les deux Cantal étudiés. Les déterminations microbiologiques effectuées à l'aide de différents milieux de culture montraient que la flore était principalement constituée de bactéries lactiques mésophiles et thermophiles. Toutefois, une microflore d'affinage très variée (probablement, propionibacteria, corynebacteria, staphylocoques et microcoques ainsi que des levures), à des niveaux de 104 à 105 ufc*g-1 a pu être identifiée et comparée aux quelques données existantes de la littérature. Une très faible teneur en bactéries indésirables (coliformes et Pseudomonas) a également été dénombrée. Un total de 44 composés volatils neutres ont été caractérisés mais comme pour de nombreuses autres variétés fromagères incluant le Cheddar, trois d'entre eux (éthanol, 2-butanone et 2-butanol) représentent plus de 95 % de l'aire totale des pics déterminés par chromatographie gazeuse couplée à la spectrométrie de masse. La comparaison détaillée des teneurs en composés volatils des deux Cantal étudiés confirmaient la différence d'activité métabolique de la microflore native des laits mis respectivement en fabrication. L'analyse de la microstructure des fromages par microscopie confocale à laser, montrait que l'essentiel de la matière grasse du Cantal se trouvait sous forme non structurée en globules mais bien sous forme d'amas de taille variable ayant une propension aisée à s'extraire de la matrice caséique, et ce particulièrement pour la matière grasse voisine de la croûte du fromage. Les résultats obtenus précisent sur de nombreux aspects les paramètres de composition du Cantal affiné. Ils ouvrent également la voie à de nouveaux travaux tant sur les cinétiques d'obtention mises en œuvre au cours du procédé de fabrication de ces paramètres que sur une meilleure connaissance du métabolisme de l'écosystème d'acidification et d'affinage.

Solutions of 100 g $\cdot$kg -1 of $\beta$-lactoglobulin ( $\beta$-Lg), $\beta$-Lg + $\alpha$-lactalbumin ( $\alpha$-La), $\beta$-Lg + $\alpha$-La + bovine serum albumin (BSA) or whey protein isolate (WPI) were heated at 75 °C, pH 6.8 in water and in the presence of either 100 mmol $\cdot$L -1 NaCl or 10 mmol $\cdot$L -1 CaCl 2. The subsequent polymerisation-aggregation processes in solution before gelation and the physical properties of the formed gels were determined. The disappearance of native-like proteins, formation of $\beta$-Lg covalent dimer and the nature of the interactions involved in the formed aggregates were addressed. Whatever the protein system, both NaCl and CaCl 2 increased gel strength and decreased gelation time. At gelling time, relatively small aggregates, formed by the contribution of the total initial amount of proteins, were observed in samples without added salts. In contrast, with NaCl or CaCl 2, only part of the initial amount of proteins was aggregated before gel time. Very large aggregates were formed in the presence of calcium. Under these two mineral conditions, as well as in samples without added salt, covalent disulphide bonds were seen to be the major forces involved in the aggregation process at gel time., Modulation de l'agrégation et de la gélification des protéines de lactosérum par les minéraux : de la $\beta$-lactoglobuline pure à l'isolat de protéines sériques. Des gels de différentes solutions de protéines ( $\beta$-lactoglobuline ( $\beta$-Lg), $\beta$-Lg + $\alpha$-lactalbumine ( $\alpha$-La), $\beta$-Lg + $\alpha$-La + sérum albumine bovine (BSA), isolat de protéines sériques) à 100 g $\cdot$kg -1 étaient formés à pH 6.8 dans l'eau ou dans 100 mmol $\cdot$L -1 NaCl ou 10 mmol $\cdot$L -1 CaCl 2. Les propriétés physiques des gels ainsi que les réactions d'agrégation des protéines (disparition des protéines natives, formation de dimères covalents de $\beta$-Lg et nature des liaisons entre protéines agrégées) ont été étudiées. Le NaCl et le CaCl 2 augmentent la force des gels et diminuent les temps de gel (tg). Au tg, sans ajout de sels, les agrégats formés, de petites tailles, impliquent la totalité des protéines présentes en solution. En revanche, en présence de NaCl ou de CaCl 2, seule une partie des protéines est impliquée dans la formation des agrégats au tg. La taille des agrégats formés est plus élevée en présence de CaCl 2. Dans toutes les conditions, les ponts disulfures interprotéiques semblent être les liaisons majoritairement impliquées dans la formation des agrégats au tg.

The influence of the origin and kind of caseinophosphopeptide (CPP) on iron absorption was assessed by comparing a commercially available CPP mixture (CPPs) and derived chromatographic fractions with the purified, chemically phosphopeptide of beta-casein [beta-CN(1-25)] using a perfused rat duodenal loop system; gluconate iron was used as control. Only iron complexed to beta-CN(1-25) displayed a better bioavailability than gluconate iron. The results obtained with various chromatographic fractions indicated that phosphopeptides of different origins (alpha(s)- versus beta-caseins) display specific effects. These findings contribute to the explanation of the discrepancy about the role of caseinophosphopeptides on mineral bioavailability in vivo.

Novel genetic variants for donkey milk lysozyme and beta-lactoglobulins I and II have been identified by the combined use of peptide mass mapping and sequencing by tandem mass spectrometry in association with database searching. The novel donkey lysozyme variant designated as lysozyme B (Mr 14,631 Da) differed in three amino acid exchanges, N49 --> D, Y52 --> S, and S61 --> N, from the previously published sequence. Three novel genetic variants for donkey beta-lactoglobulins were identified. One of them is a type beta-lactoglobulin I with three amino acid exchanges at E36 --> S, S97 --> T, and V150 --> I (beta-lactoglobulin I B, Mr 18,510 Da). The two others are type beta-lactoglobulins II with two amino acid exchanges at C110 --> P and M118--> T (beta-lactoglobulin II B, Mr 18,227 Da) and with three amino acid exchanges at D96 --> E, C110 --> P, and M118 -->T (beta-lactoglobulin II C, Mr 18,241 Da). All these primary structures are closely related to those of homologous proteins in horse milk (percent identity >96%).

International audience; The effect of the pH of skim milk (6.4 to 6.0), the casein concentration (27 to 36 g.kg$^{-1}$), a reduction in the ionic strength to 0.6 compared to that of unmodified milk and the effect of heat treatment on rennet coagulation, gel syneresis and drainage were tested. Coagulation was measured using a formagraph and by viscoelasticimetry, while syneresis was studied using a centrifugation test. Drainage was followed under conditions similar to those of cheesemaking, using either a mesophilic or thermophilic process. The effects of pH and casein concentration on rennet coagulation, gel syneresis and drainage were in accordance with those reported in the literature. Reduction in ionic strength led to shorter coagulation time and firming time. It also led to an increase in gel firmness, gel syneresis, drainage rate, final amount of expelled whey, solids content and hardness of drained curd. Ionic strength appeared to have an interactive effect with pH on coagulation and with the concentration of casein on syneresis and drainage. This effect of the reduction in ionic strength is discussed.; La coagulation présure du lait écrémé et l'égouttage : effet du pH et de la concentration en caséine, de la force ionique et du traitement thermique. L'effet du pH du lait écrémé (6,4-6,0), de la concentration en caséines (27-36 g.kg$^{-1}$), de la réduction de la force ionique du lait à 0,6 fois celle du lait natif et du traitement thermique a été testé sur la coagulation présure, l'aptitude à la synérèse et l'aptitude à l'égouttage des gels. La coagulation était suivie à l'aide du formagraph et d'un viscoélasticimètre, tandis que la synérèse était suivie par un test de centrifugation et l'égouttage était étudié par une méthode proche d'une fabrication fromagère. Les résultats confirment ceux de la littérature pour l'effet des facteurs pH et concentration en caséine sur la coagulation, la synérèse et l'égouttage. La réduction de la force ionique a entraîné une réduction du temps de prise et de raffermissement, une augmentation de la fermeté, de la synérèse, de la vitesse d'égouttage, du poids total de sérum égoutté, de l'extrait sec et de la dureté des caillés égouttés. L'effet de la force ionique est apparu en interaction avec le facteur pH lors de la coagulation et en interaction avec la concentration de caséines dans la synérèse et l'égouttage. L'effet de la réduction de la force ionique est discuté.

International audience; Camembert soft cheeses were prepared from cheese milk modified using membrane technologies to obtain different casein contents (27-37 g$\cdot$kg$^{-1}$) and different ionic strengths estimated from the dilution factor of milk with a lactose solution (0.6 compared to 1.0 in normal milk). Renneting was performed at pH 6.0 or 6.4. The amount of water remaining in the draining curds, expressed as the water to casein ratio, R (g$\cdot$g$^{-1}$), was calculated from the whey drainage kinetics data. A kinetics of variation of R during drainage was obtained in each of the experimental conditions and was characterised by fitting with a descriptive mathematical model involving 2 relaxation processes and 5 parameters: R (g water$\cdot$g$^{-1}$ casein) = R1 exp(-t/$\tau$1) + R2 exp(-t/$\tau$2) + R3. The R values at the end of drainage, obtained from the model for t = 1 000 min, fitted well with the water amounts determined in the drained curds by chemical analysis. The values of the equation parameters, obtained by fitting the equation to experimental data, were correlated to the levels of factors which were varied in the experiments. This allowed a mean value for each parameter to be obtained, and values for the effects of factors. The amount of water remaining in drained curd at the end of drainage was dependent on the milk casein content and pH at renneting factors through a negative effect. Prediction of final values of R by calculation from this data was possible. However, the correlation with experimental values was low. In addition, the drained curd composition and rheological properties were determined and the effects of the factors on these curd characteristics were quantified. A positive effect of the pH at renneting on the dry matter and ash contents of drained curd was observed. Incidentally, these factors also modified its rheological properties.; Étude de l'évolution de la teneur en eau du caillé au cours de l'égouttage, de la composition et des propriétés rhéologiques du caillé égoutté, en relation avec le pH à l'emprésurage, la teneur en caséine du lait et sa force ionique. Des fromages à pâte molle de type Camembert ont été préparés à partir de laits modifiés par des technologies à membranes pour obtenir différentes teneurs en caséine (27-37 g$\cdot$kg$^{-1}$) et différentes forces ioniques estimées d'après le taux de dilution par une solution de lactose (0,6 par comparaison à 1,0 dans le lait non modifié). L'emprésurage était réalisé à pH 6,0 ou 6,4. La quantité d'eau résiduelle dans le caillé en cours d'égouttage, exprimée par le rapport de la quantité d'eau du caillé à la quantité de caséine du lait initial, R (g$\cdot$g-1) était calculée à partir des données de l'égouttage. Une cinétique de R était obtenue pour chaque expérience d'égouttage. Un ajustement de ces cinétiques à un modèle mathématique a été réalisé en utilisant une équation à 3 étapes, R (g eau$\cdot$g$^{-1}$ caséine) = R1 exp(-t/$\tau$1) + R2 exp(-t/$\tau$2) + R3. R3 était une mesure de l'humidité du caillé en fin d'égouttage. Une valeur pour chacun des 5 paramètres de l'équation a ainsi été obtenue pour chaque expérience. Ces valeurs ont été corrélées avec le niveau des facteurs dans les expériences à l'aide d'un calcul de régression linéaire, ce qui a permis d'obtenir une valeur moyenne pour chaque paramètre et un intervalle de variation de cette moyenne, quantifiant l'effet de chaque facteur. Ces données ont été introduites dans l'équation, qui permettait alors de calculer Rcalc., une valeur prédictive pour R en fonction des niveaux choisis pour les facteurs. Pour les fromages en fin d'égouttage, la valeur de Rcalc. a été calculée (t = 1 000 min) et comparée à la teneur en eau du caillé déterminée expérimentalement par l'analyse. L'effet des facteurs sur la composition du caillé et sur ses propriétés rhéologiques a également été étudié.

Separation of milk fat in small globules (SG) (diameter lower than 2 µm) and in large globules (LG) (diameter higher than 2 µm) was realized by a patented process using special ceramic microfiltration membranes. Transformations in drinking milks, yoghourts, sour cream, camembert, Swiss cheese and butters were realized from milks of which the fat content was adjusted either by ref- erence cream or by creams issued from the SG or the LG fractions. Significant differences in texture and organoleptic properties were found in the manufactured products. Except for butter, use of milks containing small fat globules led to more onctuous products and more finer textural characteristics ver- sus products made with reference creams or with mainly large fat globules. Fat globule membrane appeared to have a high ability to bind water in cheese and so, to allow a significant increase in cheese yield.

International audience; Soft cheeses were prepared from milk modified by membrane technologies to modify the casein level (CN, 27-37 g$\cdot$kg$^{-1}$) and the whey protein to casein ratio (WP/CN, 0.12-0.24). Characterisation of milk coagulation, of whey drainage kinetics and of the drained curd was performed to quantify the effect of the parameters on the process. Moreover, the effect of pasteurisation was tested at 2 casein levels. No effect of WP/CN was observed on coagulation nor drainage. Pasteurisation induced a decrease in the drainage rate at the beginning of the process finally resulting in the same amount of whey expelled. CN had an effect on coagulation, on drainage and on drained curd composition.; Étude de l'égouttage et caractérisation du caillé égoutté en fromagerie à pâte molle, en relation avec la composition du lait (teneur en caséine et proportion protéines solubles/caséine) et la pasteurisation. Un lait de fromagerie a été traité par des technologies à membranes afin de modifier la teneur en caséine (CN, 27-37 g$\cdot$kg$^{-1}$) et le rapport de la teneur en protéines solubles à la caséine (WP/CN : 0,12-0,24). Par ailleurs, l'effet de la pasteurisation a été testé aux 2 teneurs en caséine. Des fromages de type pâte molle ont été préparés et les paramètres de coagulation et d'égouttage ainsi que les propriétés du caillé égoutté (composition et rhéologie) ont été déterminés. Aucun effet de WP/CN n'a été observé sur l'égouttage. Par contre la pasteurisation entraîne un retard de l'égouttage. Moins de sérum est recueilli au début de l'égouttage bien que la quantité de sérum total soit la même en fin d'égouttage. La teneur en caséine du lait a un effet sur la coagulation, sur la quantité de sérum obtenue, sur la cinétique de l'égouttage et sur la composition du caillé égoutté.

International audience; The probiotic application of dairy propionibacteria as well as their use in cheese technology implies exposure to various environmental stresses, including acidic pH. The acid tolerance response (ATR) of Propionibacterium freudenreichii was investigated. One strain present in Swiss-type cheese proved to be acid-tolerant, since no lethal effect was observed during exposure at pH 3. Moreover, survival at pH 2 (acid challenge) was conferred by pre-exposure to a moderate acid stress (acid adaptation). This adaptative response was triggered quickly, and showed a maximal efficiency upon exposure to pHs between 4 and 5. Stationary phase ATR and acid habituation were also demonstrated, and conferred increased survival at pH 2 without pre-exposure. Exponentially-growing bacteria were partially protected towards acidity by pre-exposure to other stresses (heat, starvation, but not hyperosmolarity). A comparative study of different strains revealed that acid stress susceptibility is strain-dependent within this species. Adaptation and survival at low pH is likely to determine the efficacy of a P. freudenreichii strain both as a cheese starter and as a probiotic.; Sensibilité et adaptation vis-à-vis du stress acide chez Propionibacterium freudenreichii subsp. shermanii . L'application probiotique des bactéries propioniques laitières, de même que leur utilisation en technologie fromagère, entraîne leur exposition à divers stress environnementaux, dont le stress acide. Nous avons étudié l'acquisition de tolérance en réponse au stress acide (ATR) chez Propionibacterium freudenreichii. Une souche présente dans un fromage à pâte pressée cuite s'est révélée tolérante, puisque aucun effet létal n'a été observé pendant une exposition à un pH de 3. De plus, la pré-exposition à un pH modérément acide (adaptation) a permis la survie à pH 2 (épreuve). Cette réponse adaptative est déclenchée rapidement et présente un optimum d'efficacité entre pH 4 et 5. L'ATR de phase stationnaire ainsi que l'habituation à l'acidité ont également été démontrées et améliorent la survie à pH 2 sans pré-traitement. Les bactéries récoltées en phase exponentielle de croissance sont partiellement protégées de l'épreuve acide par pré-exposition à d'autres stress (chaleur, carence nutritive, mais pas le stress hyperosmotique). Une étude comparative de différentes souches a révélé que la susceptibilité au stress acide dépendait de la souche au sein de cette espèce. L'adaptation et la survie à bas pH déterminent probablement l'efficacité de P. freudenreichii à la fois en tant que levain et en tant que probiotique.

Binding iron (Fe) to the 1-25 caseinophosphopeptide obtained from enzyme hydrolysis of beta casein (beta CPP) improves Fe bioavailability in the rat. To assess the mechanisms involved in its absorption, a perfused, vascularized duodenal rat loop model was used in controls and in Fe-deficient (bleeding of 25% blood volume) rats. Inhibitors of oxidative phosphorylation [2-4 dinitrophenol (DNP)] and/or of endocytosis [phenylarsine oxide (PAO)] were added to the perfusion solution containing 50 microM Fe as beta CPP bound Fe (Fe-beta CPP) or gluconate (Fe Gluc). Fe-beta CPP enhanced Fe uptake, reduced mucosal storage, and improved net absorption both in controls and in deficient animals. DNP reduced uptake, mucosal storage, and net absorption by the same percentage in Fe-beta CPP and Fe Gluc perfused rats in both control and Fe-deficient animals. PAO decreased uptake, mucosal storage, and net absorption of Fe-beta CPP but not of Fe Gluc. At the end of the experiment Fe serum levels were increased only in Fe Gluc animals. These results confirm the improved bioavailability of beta CPP bound Fe. They suggest that at least part of its absorption can occur by a different pathway than usual Fe salts. Fe-beta CPP can be taken up by endocytosis and absorbed bound to amino acids or peptides.

Caseinophosphopeptides (CPP) issued from enzyme digestion of caseins bind cations and keep them soluble in the digestive tract. They could be used as ligands to improve iron (Fe) bioavailability. Fe-deficient young rats were repleted with Fe (40 or 200 mg/kg of diet) bound either to the β-CN (1−25) of β-casein or to whole β-casein or as FeSO4. A control pair-fed group was given 200 mg of Fe (FeSO4)/kg of diet for 6 weeks. After repletion, hemoglobin concentration of the control group was reached only by the β-CN (1−25) animals fed 200 mg of Fe/kg; β-CN (1−25) bound Fe (40 and 200 mg) produced higher Fe liver and spleen stores than FeSO4. Binding Fe to the whole, nonhydrolyzed β-casein gave results intermediate between the other experimental groups. Binding Fe to phosphoserine residues of low molecular weight CPP improved its ability to cure anemia and to restore iron tissue stores, as compared to Fe bound to the whole casein and to inorganic salts. Keywords: Iron; bioavailability; tissue storage; hemoglob...

Swiss-type cheeses such as Emmental are characterized by the successive development of thermophilic lactic acid bacteria (TLAB) and propionibacteria. The aim of this study was to determine whether the choice of TLAB strain influenced propionibacteria. TLAB and propionibacteria were cultured sequentially under the conditions prevailing in cheese. Firstly, 11 Emmental juice-like media were prepared by fermenting casein-enriched milk with pure or mixed cultures of TLAB (Lactobacillus helveticus, Lb. delbrueckii subsp. lactis and Streptococcus thermophilus), differing in their proteolytic activities. TLAB cells were then removed by microfiltration. Finally, five strains of Propionibacterium freudenreichii were grown on these media at 24°C under anaerobiosis and their growth characteristics and lactate consumption determined. The media mainly differed in their contents of peptides (1·9–5·3 g/kg) and free amino acids (1·0–5·6 g/kg) and the proportions of lactate isomers (42–92% of the L(+) isomer). Propionibacteria were significantly (PL(+)-lactate and other undetermined factors. However, variations due to TLAB were less than those between propionibacteria strains.

Cheese can be considered as a paracasein network including fat and aqueous phases. Changes in the composition of the aqueous phase reflect the enzymatic and physico-chemical phe- nomena that occur in cheese during ripening. For the first time, juice was expressed by pressing from Camembert cheese ripened up to 16 d and analysed in addition to the cheese to evaluate the extent of proteolysis together with the solubilisation of minerais. The amount of expressable juice decreased sharply during ripening, i.e. from 67 to 19 % of the total water content for cheeses ripened 0 and 16 d, respectively. In parallel, the levels of pH 4.6-soluble nitrogen and non-protein nitrogen increased in the whole Camembert cheese; the increase was higher in the juice. Simultaneously, the concentration of organic phosphate in the juice increased with concomitant decreases in the concentrations of cal- cium and inorganic phosphate. This last observation suggests that salt precipitates at the surface of the cheese. The expression and subsequent analysis of juice from Camembert cheeses is an appropriate method for following the sequential action of proteolytic enzymes and minerai transfer that occur dur- ing ripening. © InralElsevier, Paris. soft cheese / aqueous phase / proteolysis / mineral/ ripening

Swiss cheese ripening: dynamics of bacterial populations and evolution of the aqueous phase composition for three industrial cheeses. To understand and control cheese ripe- ning, it is essential to know the kinetics of the microbial and biochemical changes occurring during ripening. For three Swiss cheeses industrially manufactured, differing particularly in ripening times and temperatures, we determined throughout the ripening the dynamics of starter and non-starter flora and the changes in the composition of cheese aqueous phase extracted by pressing. Three flora succeeded one another during ripening: thermophilic lactic starters, non-starter lactic acid bacteria and propionibacteria. The viability of lactic starters fell during ripening from 109 to 108-105 cfu-g " more or less rapidly, depending on the cheeses. Propionibacteria reached lOSto 4108 cfu-g'" at the end of ripening. Non-starter lactic acid bacteria grew from the beginning of ripening and reached populations as high as 108 to 5 108 cfu-g:". They were composed of heterofermentative lactobacilli, Lactobacil- lus paracasei constituting the predominant species (56% to 88% of the isolates). The aqueous phase composition showed similar changes for the three cheeses. Nitrogen matter increased from 13-18 to 54-68 g-kg" during ripening, with a rate depending on the ripening room temperature. Free amino acids increased from 10-29% to 45-47% of the nitrogen matter of the aqueous phase, but their rela- tive proportion remained essentially constant, apart from amino acids catabolised by bacteria (Arg and Asp in particular). Most minerai exchanges between curd and aqueous phase occurred before the ripening during the curd acidification, resulting in high levels of Ca, Mg and P in aqueous phase (respectively about 6.5, 0.65 and 1.2 g-kg "), Mineral composition showed only minor changes during ripening. Citrate (1.7-2.4 g·kg-I in aqueous phase at the beginning ofripening) was consumed during co Id room ripening, presumably by non-starter flora. Lactate (34-36 g·kg-I) decreased only by 1 to 2 g·kg-1 in the three cheeses. © InralElsevier, Paris.