Characterization of industrial dried whey emulsions at different stages of spray-drying

• Dry emulsions with high levels of fat are still mostly empirical in industrial plants.
• Their structure and properties are different according to where they were collected in the production process.
• Because free fat content is higher in powders from cyclones, so is coalescence.
• Indexes of instability have been created from fat droplet size distribution.

Commercial dried food emulsions, with high fat content (50 g fat /100 g), were prepared at plant scale from whey and palm oil. Five powders were analyzed: powder without fines, taken from the bottom of the spray-dryer chamber; fines 1 and fines 2 respectively collected at the bottom of the first and second cyclones, a mix of fines 1 and fines 2 and the final powder, taken during packing. Scanning electronic and optical microscopy showed only spherical particles and also indicated that fines 2 were roughly twice as smaller as other powder particles. Free fat content was significantly higher in fines than in final powder. Reconstituted emulsions (10 g powder/100 g water) were analyzed by laser light scattering. Aggregation and coalescence indexes were very low, except in reconstituted emulsions made with fines 2. This is consistent with their high free fat content and suggests that this results from processing through the cyclones.