Study of Spray-dried Yoghurt Production in a Pilot-scale Equipment Using Drying Agents to Reduce Wall Deposition

Abstract

Abstract The objective of this study was to determine suitable conditions for yoghurt spray drying in a pilot-scale equipment with a rotary atomizer using drying auxiliary agents to reduce wall deposition in the drying chamber. First, the effects of the main process variables (disk rotation speed: 25,000–30,000 rpm; inlet air temperature: 160–180 °C; feed flow rate: 5.2–8.7 kg/h) were studied with a 23 central composite experimental design. Following, six different drying agents (maltodextrins 5 dextrose equivalent [DE] and 10 DE, EmCap®, acacia gum, skimmed milk and fumed silica) were tested to identify the most promising additive to improve process yield. Excellent results on wall deposition, product recovery, product color and particle size distribution span were achieved with fumed silica Aerosil® at 3 %, 26,000-rpm atomizer speed, 160 °C inlet air temperature and 8.7 kg/h yoghurt feed flow rate. The action of the fumed silica on particle agglomerates produced a free-flowing powder with good homogeneity.