Optimization of dynamic loop mixer operating conditions for production of O/W emulsion for cell microencapsulation

Abstract

-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

Technology and potential applications of probiotic encapsulation in fermented milk products

“…Picot and Lacroix proposed easy scaled-up and low-cost microencapsulation method to improve the stability of probiotic lactic cultures and to overcome these aforementioned limits. This technique consisted of coating milk fat droplets containing powder particles of freeze-dried bacteria with whey protein polymers, using emulsification and spray drying in a continuous two-step process (Picot and Lacroix, 2003b).…”

Encapsulation Technology to Protect Probiotic Bacteria

“…It was reported that the stationary phase cultures are more resistant to heat compare to cells in exponential growth phase [61].One approach used by a number of researchers to improve probiotic survival is the addition of protectants to the media prior to drying. For example, the incorporation of thermoprotectants, such as trehalose [75], non-fat milk solids and/ or adnitol [76], growth promoting factors including various probiotic/prebiotic combinations [77] and granular starch [78] have been shown to improve culture viability during drying and storage [79,80].…”

Production of Multiphase Water‐Insoluble Microcapsules for Cell Microencapsulation Using an Emulsification/Spray‐drying Technology

“…Multiphase microcapsules were produced using a continuous 2step process, illustrated in Figure 1, which consisted of (1) preparing an o/w emulsion of AMF containing a suspension of micronized SMP used to replace freeze-dried bacteria in a heat-denatured whey protein solution and (2) spray-drying the emulsion. Preparation of soluble whey protein polymers and emulsification were carried out according to the procedures described by Picot and Lacroix (2003a). Whey protein solution containing 10% (wt/wt) solids was prepared in distilled water and kept overnight at 4°C.…”

“…006, Seepex Inc., Enon, Ohio, U.S.A.) to obtain differ-ent hydrophilic/hydrophobic phase ratios (95/5, 92.5/7.5, and 90/ 10 wt/wt) in the emulsion, for a total flow rate of 30 kg/h in the mixer. In agreement with the optimum homogenization conditions previously determined for the production of fat globules ranging from 10 to 50 m (Picot and Lacroix 2003a), the internal mixing speed was set at 2500 rpm.…”

“…Water-insoluble dry microcapsule preparations with low (<100 m) and controlled particle size are desirable for incorporation of immobilized probiotic bacteria in food products for various reasons, including higher stability, easier handling, and storage of the cultures, and limited effects on sensorial characteristics of the products, especially texture. In response to these limits, we have recently proposed an alternative low-cost cell microencapsulation method that can be easily scaled up to improve the stability of probiotic bacteria (Picot and Lacroix 2003a). The technique consists of encapsulating milk fat droplets containing dried probiotic bacteria in whey protein-based water-insoluble microcapsules, using emulsification and spray-drying in a 2-step continuous process.…”