Influence of Glass Transition on the Adhesion of Skim Milk Powder to aStainless Steel Surface

摘要

Many food powders contain amorphous glassy components, such as amorphous sugars,which when given sufficient conditions of temperature and moisture content, willmobilise as a high viscosity flow making the particles sticky. This can lead to powdercaking and increased adhesion to surfaces. The transition from the glassy state isestablished by increasing the powder temperature above its glass transition temperature.Exposing milk powder to about 10-20°C above its glass transition makes the powdermore sticky, rendering it a lot more cohesive and also increases its adhesion to a stainlesssteel surface. This work shows that skim milk powder does adhere more strongly to astainless steel wall surface when amorphous lactose is above its glass transitiontemperature and in the sticky zone. However, there is a time dependency effect becausethe molecular mobility conferring stickiness also initiates crystallisation which in-turnreduces mobility and stickiness to the wall surface over time. Furthermore, powdercaking may change the wall friction behaviour of the powder because the powder isdifferent physically.