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This article details recent research conducted on the complexation between milk proteins and polysaccharides and the properties of the complexes, and the application of such relationships to the food industry. Complexation between proteins and polysaccharides through electrostatic interactions gives either soluble complexes in a stable solution or insoluble complexes, leading to phase separation. The formation and the stability of these complexes are influenced by pH, ionic strength, ratio of protein to polysaccharide, charge density of protein and polysaccharide as well as processing conditions (temperature, shearing and time). The functional properties of milk proteins, such as solubility, surface activity, conformational stability, gelforming ability, emulsifying properties and foaming properties, are improved through the formation of complexes with polysaccharides. These changes in the functional properties provide opportunities to create new ingredients for the food industry.

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International audienceThe association of $\beta$-lactoglobulin ($\beta$-Lg) and $\alpha$-lactalbumin ($\alpha$-La) with milk fat globule membrane (MFGM), when whole milk was heated in the temperature range 60-95 °C, was investigated using one- and two-dimensional sodium dodecyl sulfate polyacrylamide gel electrophoresis (SDS-PAGE) under reducing and non-reducing conditions. In SDS-PAGE under reducing conditions, $\beta$-Lg was observed in MFGM material isolated from milk heated at $\geq$60 °C for 10 min; small amounts of $\alpha$-La and $\kappa$-casein were also observed in the MFGM material of milk heated at $\geq$65 °C for 10 min and $\geq$75 °C for 10 min, respectively. However, these proteins were not observed in SDS-PAGE under non-reducing conditions. Two-dimensional SDS-PAGE of MFGM material isolated from heated milk showed that the protein complexes that remained at the top of the non-reducing gel (first dimension) were resolved into $\beta$-Lg, $\alpha$-La and the major original MFGM proteins in the reducing gel (second dimension). These results indicate that $\beta$-Lg and $\alpha$-La associated with MFGM proteins via disulfide bonds during the heat treatment of whole milk. The amounts of $\beta$-Lg and $\alpha$-La that associated increased with an increase in the temperature up to 80 °C, and then remained almost constant. These maximum values for $\beta$-Lg and $\alpha$-La were ~1.0 mg*g-1 fat and ~0.2 mg*g-1 fat, respectively. Of the major original MFGM proteins, xanthine oxidase and butyrophilin were not affected by the heat treatment of whole milk, whereas PAS 7 was heat labile and PAS 6 decreased to some extent during heating.Interactions des protéines sériques avec les protéines de la membrane des globules gras induites par le traitement thermique du lait entier. Les interactions de la $\beta$-lactoglobuline ($\beta$-Lg) et de l'$\alpha$-lactalbumine ($\alpha$-La) avec les composants de la membrane des globules gras (MFGM), contenues dans le lait entier, chauffé entre 60 et 95 °C, ont été étudiées par électrophorèse mono ou bi-dimensionnelle, en gel de polyacrylamide et dodécyl sulfate de sodium (SDS-PAGE) en conditions réductrices ou non. En conditions réductrices, les gels de SDS-PAGE indiquaient la présence de $\beta$-Lg dans les MFGM isolés du lait chauffé dans des conditions $\geq$ à 60 °C - 10 min ; de faibles quantités d'$\alpha$-La étaient également détectées dans les MFGM pour ce même traitement thermique. Un traitement thermique plus intense ($\geq$ à 75 °C - 10 min) montrait la fixation de caséine $\kappa$. Aucune de ces interactions n'était observée en conditions SDS-PAGE non réductrices. La caractérisation en SDS-PAGE bi-dimensionnelle des MFGM isolés du lait chauffé montrait que les complexes protéiques qui restaient au sommet des gels non réducteurs (1e dimension) étaient résolus en $\beta$-Lg, $\alpha$-La et composants protéiques majeurs des MFGM en conditions réductrices (2e dimension). Ces résultats confirment l'association de la $\beta$-Lg et de l'$\alpha$-La avec les protéines d...