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A simple and easily scaled-up technology has been developed for microencapsulation of dry probiotic cultures. The microcapsules, which contained micronized skim milk powder (SMP, as a model powder) dispersed in milk fat droplets surrounded by an enteric coating (insoluble whey protein film), were produced using a continuous emulsification/spray-drying process. Microencapsulation efficiency of milk fat (MEF) and microencapsulation efficiency of SMP (MEP) in the hydrophobic phase decreased significantly (P Յ Յ Յ Յ Յ 0.05) with an increase in the "fat:whey proteins" ratio (w/w) and an increase in the SMP percentage or a decrease in the hydrophilic/hydrophobic phase ratio, respectively, whereas size of the SMP particles had no effect. Maximum values of 58 and 29% were obtained for MEF and MEP, respectively, with a 95/5 (w/w) phase ratio and 5% (w/w) of SMP in the hydrophobic phase.

-Emulsification and spray-drying were selected to develop a low-cost cell microencapsulation method adaptable to large-scale production to improve the stability of sensitive probiotic bacteria. The aim of the present study was to determine the optimum operating conditions to produce anhydrous milk fat/whey protein emulsion using a dynamic loop mixer as a first step for the microencapsulation process. The effect of various parameters of the two-phase dispersion process on fat globule size and their distribution measured at steady state was examined: the rotation speed of the helical impeller in the mixer (2000, 2500 and 3000 rpm), hydrophilic/hydrophobic phase ratio (95/5, 92.5/7.5 and 90/10 w/w), and percentage of dry material to encapsulate in the hydrophobic phase (5, 10 and 15% w/w). Fat globule size distribution was found to be only dependent on the internal mixing speed in the dynamic loop mixer (P < 0.05). A rotation speed of 2500 rpm, corresponding to a fat globule population with D[3, 2] of 23 mm, D(v, 0.1) of 15 mm, D(v, 0.5) of 25 mm, and D(v, 0.9) of 49 mm was selected for the production of multiphase spray-dried microcapsules with a diameter smaller than 100 mm, containing micronized powder particles of freeze-dried bacteria. This research showed that anhydrous milk fat/whey protein emulsions with controlled fat-globule size distribution and small size dispersion can be prepared with a continuous mode and high productivity with a dynamic loop mixer. Emulsification / dynamic loop mixer / whey protein / anhydrous milk fat / microencapsulationRésumé -Optimisation des conditions d'opération d'un mélangeur à boucles pour la production d'une émulsion de type huile-dans-eau pour l'encapsulation cellulaire. L'émulsification et le séchage par atomisation ont été sélectionnés pour développer une méthode de microencapsulation cellulaire à faible coût adaptable à une production à grande échelle pour améliorer la stabilité des bactéries probiotiques sensibles. Le but de la présente étude était de déterminer les conditions d'opération optimales permettant de produire une émulsion huile de beurre/protéines sériques en utilisant un mélangeur à boucles comme première étape du procédé de microencapsulation. L'effet de différents paramètres du procédé de dispersion de phase sur la taille des globules gras et leur distribution, mesuré à l'état stationnaire, a été par la suite étudié : vitesse de rotation de la turbine hélicoïdale dans le mélangeur (2000, 2500 et 3000 rpm), rapport phase hydrophile/phase hydrophobe (95/5, 92,5/7,5 et 90/10 p/p), pourcentage de matériel sec à encapsuler dans la phase hydrophobe (5, 10 et 15 % p/p). Il a été montré que la distribution de taille des globules