Reducing stickiness in spray dried dairy emulsions
2019
O'Neill, Graham J. | Hollingsworth, Alison | Harbourne, Niamh | O'Riordan, E Dolores
High-protein intake in early childhood may cause negative health effects in later life. However, low protein powdered follow-on milks are challenging to manufacture due to stickiness caused by increased free fat and lower glass transition points. Skim milk powder and palm oil emulsions, ranging from 0.25 to 5% w/w protein were assessed for their stability and subsequently spray dried to produce powders ranging from 1 to 20% w/w protein. Powders containing 2–8% w/w protein had high free fat levels despite the initial emulsion being stable, suggesting small adjustments in protein concentration can have a significant impact on emulsion stability during drying and atomisation. Reducing the protein content via substitution with lactose reduced the powders glass transition point (Tg) from 65 to 49 °C (powder contained 4%w/w protein, 67%w/w carbohydrate and 28%w/w fat). Substituting lactose with maltodextrin (DE6) at a 45%w/w level of inclusion increased the Tg of the powders from 50 to 113 °C, however, viscosity increased significantly. Interestingly, using glucose syrup (DE39) to substitute lactose at a 15%w/w level of inclusion, increased the powder Tg by 21 °C with no significant change in emulsion viscosity compared to a control with lactose as the sole carbohydrate. XPS analysis showed fat type (milk, palm, sunflower) influenced powder surface fat coverage. The inner fat contained increased levels of saturated fatty acids (palmitic and stearic) compared to the surface and encapsulated fat. In conclusion the Tg of low protein spray dried emulsions can be increased and the surface fat decreased, helping to reduce susceptibility to stickiness.
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