Stickiness curves of high fat dairy powders using the particle gun

High fat (>42%) dairy powders are inherently sticky due to their high levels of liquid surface fat. Incorrect operating conditions when spray drying these powders can rapidly lead to blockages. The particle gun was used to characterise the stickiness curves of high fat cream and cheese powders. Stickiness was shown to increase with increasing temperature to a maximum at 50 °C after which it decreased until no stickiness was observed above 68 °C. A dramatic increase in stickiness for the powders was found when the relative humidity of the air was increased past a certain critical point for each temperature. This was attributed to the lactose component of the powder exceeding its glass transition temperature by a critical amount. Best estimates of the (T−Tg)crit. values for White Cheese Powder, Low Fat Cream Powder and High Fat Cream Powder were 28, 37 and 38 °C, respectively.