Unité de Recherche Technologie et Analyses Laitières

To evaluate the importance of protein digestion rate on protein deposition, we characterized leucine kinetics after ingestion of "protein" meals of identical amino acid composition and nitrogen contents but of different digestion rates. Four groups of five or six young men received an L-[1-13C]leucine infusion and one of the following 30-g protein meals: a single meal of slowly digested casein (CAS), a single meal of free amino acid mimicking casein composition (AA), a single meal of rapidly digested whey proteins (WP), or repeated meals of whey proteins (RPT-WP) mimicking slow digestion rate. Comparisons were made between "fast" (AA, WP) and "slow" (CAS, RPT-WP) meals of identical amino acid composition (AA vs. CAS, and WP vs. RPT-WP). The fast meals induced a strong, rapid, and transient increase of aminoacidemia, leucine flux, and oxidation. After slow meals, these parameters increased moderately but durably. Postprandial leucine balance over 7 h was higher after the slow than after the fast meals (CAS: 38 +/- 13 vs. AA: -12 +/- 11, P < 0.01; RPT-WP: 87 +/- 25 vs. WP: 6 +/- 19 micromol/kg, P < 0.05). Protein digestion rate is an independent factor modulating postprandial protein deposition.

The production of homopolysaccharides (dextrans, mutans) and heteropolysaccharides by lactic acid bacteria, their chemical composition, their structure and their synthesis are outlined. Mutans streptococci, which include Streptococcus mutans and S. sobrinus produce soluble and insoluble alpha-glucans. The latter may contain as much as 90% alpha-1-3 linkages and possess a marked ability to promote adherence to the smooth tooth surface causing dental plaque. Dextrans produced by Leuconostoc mesenteroides are high molecular weight alpha-glucans having 1-6, 1-4 and 1-3 linkages, varying from slightly to highly branched; 1-6 linkages are predominant. Emphasis is put on exopolysaccharide producing thermophilic and mesophilic lactic acid bacteria, which are important in the dairy industry. The produced polymers play a key role in the rheological behaviour and the texture of fermented milks. One of the main problems in this field is the transitory nature of the thickening trait. This instability is not yet completely understood. Controversial results exist on the sugar composition of the slime produced, but galactose and glucose have always been identified with galactose predominating in most cases.

In young men ingesting protein meals, slowly digested proteins (caseins: CAS) induce a higher protein gain than those that are rapidly digested (whey proteins: WP). Our aim was to assess whether or not this is true in elderly men receiving mixed meals. The effects of meals containing either CAS or two different amounts of WP (WP-iN: isonitrogenous with CAS, or WP-iL: providing the same amount of leucine as CAS) on protein metabolism (assessed by combining oral and intravenous leucine tracers) were compared in nine healthy, elderly (mean +/- S.E.M. age 72 +/- 1 years) and six young men (24 +/- 1 years). In both age groups, WP-iL and WP-iN were digested faster than CAS (P < 0.001, ANOVA). Proteolysis was inhibited similarly whatever the meal and age groups (P = NS). Protein synthesis was higher with WP-iN than with CAS or WP-iL (P < 0.01), irrespective of age (P = NS). An age-related effect (P < 0.05) was found with postprandial leucine balance. Leucine balance was higher with CAS than with WP-iL (P < 0.01) in young men, but not in elderly subjects (P = NS). In isonitrogenous conditions, leucine balance was higher with WP-iN than with CAS (P < 0.001) in both age groups, but the magnitude of the differences was higher in the elderly men (P = 0.05). In conclusion, during aging, protein gain was greater with WP (rapidly digested protein), and lower with CAS (slowly digested protein). This suggests that a 'fast' protein might be more beneficial than a 'slow' one to limit protein losses during aging.

Seven cDNA clones corresponding to the rab1, rab2, rab3A, rab3B, rab4, rab5, and rab6 genes were isolated from a human pheochromocytoma cDNA library. They encode 23-25 kDa polypeptides which share approximately 30-50% homology and belong to the ras superfamily. The rab1, rab2, rab3A, and rab4 proteins are the human counterparts of the rat rab gene products that we have previously characterized. Comparison of the seven human rab proteins with the yeast YPT1 (YPT1p) and SEC4 (SEC4p) proteins reveals highly significant sequence similarities. H-rab1p shows 75% amino acid identity with YPT1p and may be therefore considered as its human counterpart. The other proteins share approximately 40% homology with YPT1p and SEC4p. The homology (approximately 30%) between these rab proteins and p21ras is restricted to the four conserved domains involved in the GTP/GDP binding. Human rab proteins were produced in Escherichia coli. Large amounts of rab proteins in soluble form can be extracted and purified without the use of detergents. All six proteins bind GTP and exhibit GTPase activities. A possible involvement of the rab proteins in secretion is discussed.

In all, 4379 isolates from 35 products, including 24 artisanal cheeses, were surveyed with a view to identifying strains that could be used as starters in commercial dairy fermentations. Of the isolates, 38% were classified as Lactococcus , 17% as Enterococcus , 14% as Streptococcus thermophilus , 12% as mesophilic Lactobacillus , 10% as Leuconostoc and 9% as thermophilic Lactobacillus . Acid production by the isolates varied considerably. Of the 1582 isolates of Lactococcus and 482 isolates of mesophilic Lactobacillus tested, only 8 and 2% respectively produced sufficient acid to lower the pH of milk to &lt;5·3 in 6 h at 30°C. In contrast, 53, 32 and 13% of Str. thermophilus , thermophilic Lactobacillus and Enterococcus isolates respectively reduced the pH to 5·3. These isolates were found only in some French, Italian and Greek cheeses. Bacteriocins were produced by 11% of the 2257 isolates tested and 26 of them produced broad-spectrum bacteriocins which inhibited at least eight of the ten target strains used, which included lactic acid bacteria, clostridia and Listeria innocua . The most proteolytic of the 2469 isolates tested were Str. thermophilus from Fontina cheese followed by Enterococcus from Fiore Sardo and Toma cheese and thermophilic Lactobacillus from all sources. Exopolysaccharides were produced by 5·3% of the 2224 isolates tested.

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 transmembrane hydraulic pressure concept (UTP) with its different ways of carrying out microfiltrate recirculation, longitudinal porosity gradient and of new ceramic membrane materials allows nowadays 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 Rsum -Dveloppements actuels de la technologie de microfiltration dans l'industrie laitire. Cet article traite des dveloppements les plus rcents, certains tout juste brevets, de la microfiltration tangentielle dans l'industrie laitire. La combinaison de l'utilisation du concept de pression transmembranaire uniforme, avec ses diffrentes possibilits de mise en oeuvre : recirculation du microfiltrat, gradient de porosit longitudinal, et de nouveaux matriaux membranaires cramiques

Lactic acid bacteria can produce a variety of substances with antibacterial activity which are described in this article. Non-peptide antibacterial substances are distinguished from bacteriocins, which have a proteinaceous active site. Among the former, reuterin produced by Lactobacillus reuteri is a broad spectrum inhibitor active against Gram-positive and Gram-negative bacteria, yeasts, molds and protozoas. It is a glycerol derivative, l3-hydroxypropionaldehyde.

Milk contains a lot of different components with their own functional properties and some of them, such as casein, have been used in the manufacture of non-food technical products for many years. The present review deals with the non-food applications of (i) the major individual components of milk: proteins (casein; soluble proteins); lactose; milk fat and (ii) whey, a co-product of cheese and casein manufacture. New applications of milk proteins on a laboratory scale are focused on the manufacture of protein-based films and biomaterials. Also, fermentation of lactose and whey provides low molecular weight compounds and exopolysaccharides. These promising routes for giving added value to dairy co-products and effluents should be applied to achieving a great reduction in dairy industry wastes.

This review reports recent data regarding the metabolism and biochemistry of Streptococcus salivarius subsp thermophilus and Lactobacillus delbrueckii subsp bulgaricus related to yogurt manufacture. The taxonomy of these bacteria is presented. Different proposed pathways for carbohydrate metabolism are then discussed, as weil as recent molecular and genetic studies of the enzymes involved. Acetaldehyde is the major aromatic compound in yogurt, and so the different pathways of its formation are briefly described. Recent studies have concerned threonine aldolase which catalyzes acetaldehyde synthesis by yogurt bacteria. Exocellular polysaccharides produced by lactic acid bacteria improve the texture of stirred and liquid yogurts. Some of the polysaccharides of yogurt bacteria are currently known and particular aspects of their production are discussed. Some other properties, le proteolysis, Iipolysis, urease, oxygen metabolism, are also briefly presented. Interactions between streptococci and lactobacilli are weil established, but more data are required for the complete characterization and control of mixed populations. In particular, Iittle is known about antimicrobial compounds produced by these microorganisms. Bacteriophages of yogurt bacteria are now weIl characterized, but liltle is known about Iysogeny in thermophilic streptococci. Finally, progress in genetics (on both plasmid and chromosomal DNA) is briefly discussed.

This study presents milk fat globule refractive index (n i ) and absorption coefficient (k a ) values that can be used reliably for particle size distribution measurements by Laser Light Scattering at two different wavelengths. A k a 10 -5 was obtained for liquid milk fat. The n i of milk fat globules at 20 o C was measured at 589 nm and was calculated to be 1.470 at 466 nm and 1.460 at 633 nm. Because the software of the LLS equipment does not allow for differences in n i,water at the two different wavelengths, n i,fat was corrected to reflect the difference between the refractive indices of the fat globule and its surrounding medium at each wavelength. For example, if n i,water is taken to be 1.33, then for milk fat globules the corrected value is 1.458 at 633 nm and 1.460 at 466 nm. These optical parameters led to reliable milk fat globule size distributions. In any case, k a must never be overestimated, since this leads to artefactual peaks. milk fat / fat globule / refractive index / particle size distribution / laser light scattering / optical property Rsum -Proprits optiques des globules gras du lait pour les mesures en granulomtrie laser. Dans cette tude, nous prsentons des valeurs de l'indice de rfraction (n i ) et du coefficient d'absorption (k a ) des globules gras du lait, deux diffrentes longueurs d'onde, qui sont fiables pour des mesures de granulomtrie laser diffraction de la lumire. Une valeur de k a 10 -5 est obtenue pour la matire grasse laitire liquide. L'indice n i des globules gras 20 o C est mesur 589 nm ; sa valeur calcule est alors de 1,470 466 nm et 1,460 633 nm. Comme il n'est pas possible d'entrer des valeurs de n i,eau diffrentes pour les deux longueurs d'ondes , on utilise des valeurs corriges de n i,globule pour maintenir correcte la diffrence d'indice de rfraction entre les globules gras et l'eau chaque . Par exemple, si l'on considre n i,eau = 1,33 pour les deux , alors pour les globules gras la valeur corrige est de 1,458 633 nm et 1,460 466 nm. Ces paramtres optiques permettent d'obtenir des distributions granulomtriques fiables pour les globules gras du lait. La valeur de k a ne doit jamais tre surestime car cela entrane l'apparition de populations artfactuelles.

Current strategies to prevent or treat human papillomavirus type 16 (HPV-16) infection are promising, but remain costly. More economical but efficient vaccines are thus needed. In this study, we evaluated the protective effects of mucosally coadministered live Lactococcus lactis strains expressing cell wall-anchored E7 Ag and a secreted form of IL-12 to treat HPV-16-induced tumors in a murine model. When challenged with lethal levels of tumor cell line TC-1 expressing E7, immunized mice showed full prevention of TC-1-induced tumors, even after a second challenge, suggesting that this prophylactic immunization can provide long-lasting immunity. Therapeutic immunization with L. lactis recombinant strains, i.e., 7 days after TC-1 injection, induced regression of palpable tumors in treated mice. The antitumor effects of vaccination occurred through a CTL response, which is CD4+ and CD8+ dependent. Furthermore, immunized mice developed an E7-specific mucosal immune response. These preclinical results suggest the feasibility of the low-cost mucosal vaccination and/or immunotherapy strategies against HPV-related cervical cancer in humans.

The storage modulus G' of rennet and acid milk gels filled with milk fat globules was measured as a function of the fat globule surface composition (native milk fat globule membrane, caseins and whey proteins, or a mixture of the three due to mechanical treatments) and surface area (i.e., the fat globule size). By different technological procedures, it was possible to obtain fat globules of constant surface composition but various sizes, and vice-versa, which had never been done. For both rennet and acid gels, a critical fraction of the fat globule surface covered by caseins and whey proteins was identified (approximately 40%), beyond which G' increased. Below this threshold, the gel viscoelasticity was unaffected by mechanical treatments. When the diameter of native milk fat globules decreased, the G' of rennet gels increased slightly, whereas that of acid gels decreased sharply. For both types of gels, G' increased when the diameter of partially disrupted fat globules decreased. For recombined globules completely covered with caseins and few whey proteins, G' increased with fat globule surface area for rennet gels whereas it decreased for acid gels. With the help of confocal microscopy and in the light of general structural differences between rennet and acid gels, a mechanism is proposed for the effect of fat globule damage and diameter on G', depending on the interactions the globules can undergo with the casein network.

&mdash; The effects of daily herbage allowance (DHA = herbage mass [HM] x daily offered area [DOA]) and cow characteristics upon herbage intake at grazing were assessed in two experiments. In n experiment 1, two DHA (low and medium, 19 and 26 kg organic matter [OM]/cow/day) were com- pared in a continuous design using two groups of five cows. In experiment 2, three DHA (low, medium and high, 19, 29 and 46 kg OM/cow/day) were compared in a 3 x 3 latin square design using three groups of five cows. Mid-lactating cows (six first lactation per trial) were used. Fat-corrected milk at turnout (FCMt) ranged between 17 to 35 kg and live weight (LW) from 510 to 680 kg. Cows strip-grazed plots of vegetative Lolium perenne and did not receive concentrates. Herbage mass cut to ground level (HM) ranged from 3.5 to 7.1 t OM/ha. In experiment 1, herbage organic matter intake (HOMI) (13.5 vs 14.9 kg/day) and FCM yield (20.6 vs 22.0 kg/day) tended to increase from low to medium DHA but dif- ferences were not significant. In experiment 2, HOMI increased in a quadratic manner (13.8, 16.2 and 16.7 kg/day) and FCM increased linearly (P < 0.01 ) with DHA (20.4, 21 .7 and 23.0 kg/day for low, medium and high DHA, respectively). In both experiments, HOMI was consistently lower in first lac- tation compared to adult cows and large between-cow variations within lactation were noted. From the pooled data, HOMI was related to DHA and cow characteristics: HOMI = 7.9 -98 DHA-1 + 0.264 FCMt + 0.0073 LW (n = 95, R 2 = 0.60, rsd = 1.77 kg). However, splitting DHA into its two components accounted for more of the variance in HOMI: HOMI =-20.4 -115 DOA-1 + 9.63 HM -0.873 HM 2 + 0.266 FCMt + 0.0095 LW (R 2 = 0.70, rsd = 1.56 kg). These relationships showed that HOMI was affected by DHA but the original sward herbage mass/structure does have an independant effect in regulating intake. Moreover, voluntary intake increases with the potential of milk yield and this increase could account for the two-thirds of the supplementary energy requirements. dairy cows / grazing / intake / herbage allowance / animal requirements Rsum &mdash; Effet des quantits d'herbe offertes, de la biomasse et des caractristiques ani- males sur l'ingestion des vaches laitires au pturage. L'effet de la quantit d'herbe alloue (DHA = biomasse (HM) x surface offerte journellement (DOA)) et des caractristiques des animaux sur les quantits de MO d'herbe ingres au pturage (HOMI) ont t analyses au cours de deux essais. Dans l'essai 1, deux niveaux de DHA (Bas et Moyen, 19 et 26 kg MO/vache/jour) ont t compars dans un schma en continu en utilisant deux groupes de cinq vaches apparies. Dans le second essai, trois niveaux d'herbe alloue (Bas, Moyen et Haut ; 19, 29 et 46 kgljour) ont t compars dans un schma en carr latin 3 x 3 en utilisant trois lots de cinq vaches. Tous les animaux taient en milieu de lactation et six primipares ont t utilises par essai. la mise l'herbe, la production de lait 4 % (FCMt) et le poids vif (LtN) variaient de 17 35 kgljour et de 510 680 kg. Les vaches n'ont pas reu de concentr et ont t conduites en pturage rationn sur prairies de ray-grass anglais pendant toute la dure des essais. La biomasse coupe au niveau du sol a vari de 3,5 7,1 t MOlha entre les priodes. Dans l'essai 1, HOMI (13,5 versus 14,9 kglj) et la production de la 4 % (20,6 versus 22,0 kgljour) ont eu tendance augmenter entre le traitement Bas et Moyen mais les diffrences n'ont pas t significatives. Dans l'essai 2, HOMI a augment de manire curvilinaire (13,8 ; 16,2 ; 16,7 kgljour) et la production de lait 4 % a augment linairement avec le niveau d'herbe alloue (20,4; 21,7 et 23,0 kgljour). HOMI a toujours t beaucoup plus faible pour les vaches primipares que les vaches adultes et des diffrences interindividuelles importantes sont apparues pour un mme rang de lactation. partir de l'ensemble des donnes individuelles nous avons montr que HOMI peut tre prdite partir de DHA et des caractristiques des animaux : HOMI = 7,9 -98 DHA-1 + 0,264 FCMt+ 0,0073 LVV (n = 95, R 2 = 0,6 0 , etr= 1,77kg). Cependant, la prcision de ce modle est sensiblement amliore lorsque l'on considre sparment les deux composantes de DHA : HOMI = -20,4 -115 DOA-I + 9,63 HM -0,873 HM 2 + 0,266 FCMt + 0, 0095 LW(R2 = 0, 70, etr = 1,56 kg). Ces relations montrent que HOMI est affecte par DHA mais aussi que la biomasse et/ou la structure ini- tiale de la prairie affecte galement les quantits ingres. De plus les quantits ingres augmentent avec le potentiel de production des animaux et cet accroissement couvre environ les deux tiers des besoins supplmentaires de production pour des pturages de bonne qualit.

Strains of Lactobacillus plantarum were grown and stored in cherry (ChJ), pineapple (PJ), carrot (CJ), and tomato (TJ) juices to mimic the chemical composition of the respective matrices. Wheat flour hydrolysate (WFH), whey milk (W), and MRS broth were also used as representatives of other ecosystems. The growth rates and cell densities of L. plantarum strains during fermentation (24 h at 30°C) and storage (21 days at 4°C) differed only in part, being mainly influenced by the matrix. ChJ and PJ were the most stressful juices for growth and survival. Overall, the growth in juices was negatively correlated with the initial concentration of malic acid and carbohydrates. The consumption of malic acid was noticeable for all juices, but mainly during fermentation and storage of ChJ. Decreases of branched-chain amino acids (BCAA)-with the concomitant increase of their respective branched alcohols-and His and increases of Glu and gamma-aminobutyric acid (GABA) were the main traits of the catabolism of free amino acids (FAA), which were mainly evident under less acidic conditions (CJ and TJ). The increase of Tyr was found only during storage of ChJ. Some aldehydes (e.g., 3-methyl-butanal) were reduced to the corresponding alcohols (e.g., 3-methyl-1-butanol). After both fermentation and storage, acetic acid increased in all fermented juices, which implied the activation of the acetate kinase route. Diacetyl was the ketone found at the highest level, and butyric acid increased in almost all fermented juices. Data were processed through multidimensional statistical analyses. Except for CJ, the juices (mainly ChJ) seemed to induce specific metabolic traits, which differed in part among the strains. This study provided more in-depth knowledge on the metabolic mechanisms of growth and maintenance of L. plantarum in vegetable and fruit habitats, which also provided helpful information to select the most suitable starters for fermentation of targeted matrices.

The objective of this study was to determine whether processing could modify the resistance of casein (CN) to digestion in infants. A range of different dairy matrices was manufactured from raw milk in a pilot plant and subjected to in vitro digestion using an infant gut model. Digestion products were identified using MS and immunochemical techniques. Results obtained showed that CNs were able to resist digestion, particularly κ- and αs(2)-CN. Resistant areas were identified and corresponded to fragments hydrophobic at pH 3.0 (gastric conditions) and/or carrying post-translational modifications (phosphorylation and glycosylation). Milk processing led to differences in peptide patterns and heat treatment of milk tended to increase the number of peptides found in digested samples. This highlights the likely impact of milk processing on the allergenic potential of CNs.

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When cultivated in the presence of trypsin, the Ruminococcus gnavus E1 strain, isolated from a human fecal sample, was able to produce an antibacterial substance that accumulated in the supernatant. This substance, called ruminococcin A, was purified to homogeneity by reverse-phase chromatography. It was shown to be a 2,675-Da bacteriocin harboring a lanthionine structure. The utilization of Edman degradation and tandem mass spectrometry techniques, followed by DNA sequencing of part of the structural gene, allowed the identification of 21 amino acid residues. Similarity to other bacteriocins present in sequence libraries strongly suggested that ruminococcin A belonged to class IIA of the lantibiotics. The purified ruminococcin A was active against various pathogenic clostridia and bacteria phylogenetically related to R. gnavus. This is the first report on the characterization of a bacteriocin produced by a strictly anaerobic bacterium from human fecal microbiota.

Abstract Abstract This review summarizes the recent developments in understanding of the relationships between the diet of animals and the sensory quality of dairy products. Feeding dairy cattle with maize silage by comparison with hay or grass silage leads to whiter and firmer cheeses and butter and sometimes to differences in flavour. Major differences in sensory characteristics were observed between cheeses made with milk produced by cows on winter diets (based on hay and grass silage) or turned out to pasture in the spring. Conversely, preserving grass as silage, by comparison with hay, has no major effect on cheese sensory characteristics, except on colour, the cheese being yellower with grass silage. Several recent experiments have shown a significant effect of grass botanical composition on cheese texture and flavour. These effects are due to the presence in milk of specific molecules directly introduced by feeding (carotenes, terpenes) or produced by the animals (plasmin, fatty acids) under the effect of specific diets.

Tolerance to digestive stresses is one of the main factors limiting the use of microorganisms as live probiotic agents. Susceptibility to bile salts and tolerance acquisition in the probiotic strain Propionibacterium freudenreichii SI41 were characterized. We showed that pretreatment with a moderate concentration of bile salts (0.2 g/liter) greatly increased its survival during a subsequent lethal challenge (1.0 g/liter, 60 s). Bile salts challenge led to drastic morphological changes, consistent with intracellular material leakage, for nonadapted cells but not for preexposed ones. Moreover, the physiological state of the cells during lethal treatment played an important role in the response to bile salts, as stationary-phase bacteria appeared much less sensitive than exponentially growing cells. Either thermal or detergent pretreatment conferred significantly increased protection toward bile salts challenge. In contrast, some other heterologous pretreatments (hypothermic and hyperosmotic) had no effect on tolerance to bile salts, while acid pretreatment even might have sensitized the cells. Two-dimensional electrophoresis experiments revealed that at least 24 proteins were induced during bile salts adaptation. Identification of these polypeptides suggested that the bile salts stress response involves signal sensing and transduction, a general stress response (also triggered by thermal denaturation, oxidative toxicity, and DNA damage), and an alternative sigma factor. Taken together, our results provide new insights into the tolerance of P. freudenreichii to bile salts, which must be taken into consideration for the use of probiotic strains and the improvement of technological processes.

Le phosphocasinate natif (PPCN) tait spar du lait cru par microfiltration tangentielle sur membrane (diamtre des pores: 0,2 l1m) suivie d'une purification par diafiltration avec de l'eau. Le suivi analytique des liquides obtenus de part et d'autre de la membrane montrait une permation conforme aux lois de la filtration des protines majeures du lactosrum (j3-lactoglobuline et a-lactalbumine), du lactose et des sels minraux solubles et au contraire, une rtention leve des composants solubles haut poids molculaire ainsi que des protoses-peptones. Le rtentat final tait sch par atomisation. Ses teneurs en matire azote (N x 6,38) et en cendres taient respectivement de 89% et de 9% par rapport la substance sche. L'aptitude la coagulation par la prsure, de la solution reconstitue a t compare celle du lait cru. Le temps de coagulation est rduit de 53%; la cintique d'organisation du. gel (apprcie par le K2Q) et la fermet finale (apprcie 30 min) sont galement accrues de plus de 50%. La proprit de former un gel sous l'action de la prsure aprs un traitement thermique de 100 oC -5 min est conserve, contrairement au lait qui, soumis au mme traitement, ne coagule plus. microfiltration 1 phosphocasinate 1 coagulation prsure 1 traitement thermique Summary -Native micellar casein separation through cross flow membrane microfiltration. Native phosphocaseinate (PPCN) was separated from raw milk by tangential membrane microfiltration (pore diameter: 0.2 um) followed by purification through water diafiltration. Analytical survey of both tiquids issued by membrane treatment showed permeation rates matching mathematical laws for the main whey proteins (fJ-lactoglobulin and a-Iactalbumin), lactose and soluble mineraI salts. On the contrary, a high retention of high molecular weight soluble components and proteose-peptone fraction was observed. Finaldiafiltratedretentate was spray-dried. Its protein (N x 6.38) and ash contents in total solids were respectively 89% and 9%. Rennet coagulating ability of PPCN reconstituted solution was compared to that of raw milk. Coagulation time was reduced by 53%; gel development kinetics (estimated by Krol and final firmness (estimated at 30 min) were increased by more than 50%. When a severe heat treatment (100 oC -5 min) was applied, milk lost its ability to coagulate alter rennet action; PPCN solution did not, but ifs coagulation time was increased and the curd was slightly weaker.