-Camembert cheeses were produced using either small (~3 mm, SFG) or large (~6 mm, LFG) native milk fat globules obtained by a patented microfiltration process. The composition of the cheese milk did not depend on the fat globule size. Less whey was extracted from the SFG cheeses, that subsequently contained more moisture than LFG cheeses throughout the ripening period. The SFG curds were less rigid and less firm than the LFG ones and underwent greater proteolysis during ripening. Camembert cheeses with small fat globules had a higher melting and elastic texture, a higher flowing aspect and were less yellow. The results were explained (i) by the greater surface area of native milk fat globule membrane for SFG vs. LFG, at a given fat content, and (ii) by the thinner casein strands in SFG cheeses due to the smaller interglobular distance. The use of native milk fat globules with different sizes can thus lead to new products with different technological and sensory properties.Milk fat / fat globule / Camembert cheese / cheese yield / rheology / particle size / microfiltration / sensory analysis Résumé -Des propriétés physico-chimiques et sensorielles du Camembert sont affectées par la taille des globules gras natifs du lait. Des camemberts ont été fabriqués en utilisant des globules gras natifs du lait de petit diamètre (~3 mm) ou de grand diamètre (~6 mm), obtenus par un procédé de microfiltration breveté. La composition des laits de fromagerie ne dépend pas de la taille des globules gras. Il s'égoutte moins de sérum des camemberts à petits globules, qui sont ensuite plus humides que les fromages à gros globules au cours de l'affinage. Les caillés à petits globules sont moins fermes et moins rigides que ceux à gros globules et sont plus protéolysés durant l'affinage. Les camemberts à petits globules ont une texture plus fondante et plus élastique, sont plus coulants et moins jaunes. Ces résultats peuvent être expliqués (i) par la plus grande surface de membrane native pour les petits globules par rapport aux gros globules à une teneur donnée en matière grasse et (ii) par la moindre épaisseur des brins de caséine dans les camemberts à petits globules, à cause de la plus faible distance moyenne entre globules. L'utilisation de globules gras natifs du lait de différentes tailles peut donc aboutir à de nouveaux produits présentant des propriétés technologiques et sensorielles différentes.Matière grasse du lait / globule gras / Camembert / rendement fromager / granulométrie / rhéologie / analyse sensorielle / microfiltration

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-Emmental cheeses were produced using either small (~3 µm, SFG) or large (~6 µm, LFG) native milk fat globules obtained by a patented microfiltration process. Ripened SFG cheeses were less flexible and less firm than LFG cheeses. Indeed, the SFG cheeses contained more moisture and underwent greater proteolysis than the LFG cheeses 52 d after manufacture. However, lipolysis was three-fold lower in SFG cheeses. This was linked to the milk fat structure in Emmental cheese: larger inclusions of denuded destabilized fat were observed in LFG cheeses, whereas more fat globules were observed in SFG cheeses. One Emmental cheese was produced using homogenized milk fat globules, in which lipolysis was dramatically increased and unacceptable. For a given size range, the structure of milk fat is thus of tremendous importance regarding lipolysis and small natural milk fat globules cannot be replaced by homogenized ones. The melting temperature and solid fat content of fat in Emmental cheese increased with native fat globule size. This is related to the improved functional properties of SFG cheeses, i.e., increased stretching, elastic increase and melting, and lower extrusion force compared with LFG cheeses. This study confirms, as previously pioneered using Camembert cheese manufacturing technology, that the use of native milk fat globules with different sizes can lead to a range of new dairy products with different physico-chemical and functional properties.Milk fat / fat globule / Emmental cheese / cheese yield / rheology / particle size / microfiltration / functional property Résumé -Des propriétés physico-chimiques et fonctionnelles de l'emmental sont affectées par la taille des globules gras natifs du lait. Des emmentals ont été fabriqués en utilisant des globules gras natifs du lait de petit diamètre (~3 µm) ou de grand diamètre (~6 µm), obtenus par un procédé de microfiltration breveté. Les fromages affinés à petits globules sont moins souples et moins fermes que ceux à gros globules. En effet, les fromages à petits globules sont plus humides et plus protéolysés à 52 j d'affinage. Cependant, la lipolyse est trois fois moindre dans les fromages à petits globules, ce qui est lié à la structure de la matière grasse dans les emmentals : les emmentals à gros globules présentent de plus grandes inclusions de matière grasse déstabilisée, tandis que ceux à petits globules semblent contenir plus de globules gras. Un emmental a été fabriqué avec des globules * Corresponding author: mcmichal@labtechno.roazhon.inra.fr 344 M.-C. Michalski et al.

The experiments reported in this study give deeper insight into the crystallization of milk fat in Emmental cheese, which is the most widely consumed hard cheese in France. Differential scanning calorimetry (DSC) was used to monitor the thermal properties of milk fat after the main stages involved during manufacture of Emmental cheese. By heating the samples to 60 degrees C to eliminate their thermal history and cooling them at 2 degrees C/min, the liquid --> solid phase transition of fat was investigated. Confocal laser scanning microscopy was used to characterize in situ the supramolecular organization of milk fat dispersed in the casein matrix. The destabilization of fat globules by aggregation or coalescence and the formation of free fat during the manufacture altered the thermal properties of milk fat by increasing the initial temperature of crystallization and by the formation of 2 overlapping exotherms. The melting properties of the crystalline structures formed by fat at the temperatures used for ripening (12, 21, and 4 degrees C) were examined. Differential scanning calorimetry was used to determine the ratio of solid to liquid fat; that is, the amount of fat that is crystallized, by dividing the partial enthalpy of melting of the fat for ripening temperature by the total enthalpy of melting of the same fat extracted from cheese. This study shows, for the first time, that milk fat is partially crystallized in Emmental cheese: about 55.7 +/- 3.5% of fat is solid at 4 degrees C at the end of ripening. Polymorphic phase transitions of milk fat are also suggested during ripening of Emmental cheese.

Bioactive lipids of the milk fat globule membrane become concentrated in two co-products of the butter industry, buttermilk and butterserum. Their lipid composition is detailed here with special emphasis on sphingolipid composition of nutritional interest, determined using GC, HPLC and tandem mass spectrometry. Butterserum was 2.5 times more concentrated in total fat than buttermilk, with 7.7±1.5vs 19.5±2.9wt% and even more concentrated in polar lipids, with 1.4±0.2vs 8.5±1.1wt%. Both ingredients constitute concentrated sources of sphingomyelin (3.4-21mg/g dry matter) and contained low amounts of bioactive ceramides in a ratio to sphingomyelin of 1:5mol% in buttermilk and 1:10mol% in butterserum. Compared to other natural lecithins, these two co-products are rich in long and saturated fatty acids (C22:0-C24:0), contain cholesterol and could have interesting applications in neonatal nutrition, but also as brain-protective, hepatoprotective and cholesterol lowering ingredients.