Use of different supports for oil encapsulation in powder by spray drying
Résumé
Spray drying of oil-in-water emulsions containing hydrophilic carriers is used to encapsulate lipophilic compounds into powders. Oil droplets are dispersed within the solid matrix of carriers acting like a barrier. To study the influence of the nature of the carrier on both the properties of the initial and dry emulsion and on the spray drying process, alpha-tocopherol dispersed in olive oil (weight ratio 1/4) was used as a model lipophilic molecule. Eight initial oil-in-water emulsions containing 4% w/w oil phase and 36% w/w carrier consisting of different food polymers as maltodextrin DE12, acacia gum and inulin, mixed in different proportions were prepared by rotor-stator homogenization and characterized for their size, size distribution and viscosity. They were spray dried in a pilot spray dryer in the same conditions (inlet and outlet air temperatures of 180 degrees C and 90 degrees C respectively, emulsion flow rate 57 g.min(-1)) and the properties of the dry emulsions produced were characterized. Whatever the support used, the powder yield of the spray drying process was higher than 50% without optimization of the operating conditions. The dry emulsions produced had similar properties (size, size distribution, density and flowability) and contained more than 73% of the initial oil with only 5% of the oil phase on the particle surface (unencapsulated). After powder dissolution in water, the reconstituted emulsions had a size distribution similar to that of the initial emulsions, indicating that spraying did not modify the emulsion structure. Due to its emulsifying and film forming properties, the use of acacia gum, in combination with maltodextrin and/or inulin, allowed obtaining more stable initial emulsions with controlled size distribution (similar to 2 mu m, monodispersed) leading to higher powder yield for spray drying (e.g., superior to 65%). Agave inulin was found to be a possible alternative to maltodextrin to produce powders with increased health benefits.