Stickiness of maltodextrins using probe tack test during in-situ drying

Abstract

A probe tack test was used to map the level of stickiness of droplets containing 20 and 40 wt% of maltodextrins DE5, DE10 and DE18 as they dried at 40 and 78 °C. As skin formation progressed, the stickiness increased to a maximum then decreased in most cases until the droplet was no longer sticky (non-adhesive state). The results show the expected trends; lower DE maltodextrins (higher molecular weight) were sticky for only a short time over a narrow range of bulk moisture contents, and addition of glycerol and maltodextrin DE18 to maltodextrin DE5 act as plasticisers resulting in a broadening of the stickiness profiles. Glass transition temperatures were measured for each maltodextrin at a range of moisture contents. They indicate that the solutions should be sticky when, in fact, the probe tack tests show that they are non-adhesive. This indicates a difference between the surface and the bulk measured moisture content and possibly also temperature, as expected in a drying system. However, because surface moisture content and temperature can not be measured, the stickiness results were not able to be directly related to the surface glass transition temperature of the maltodextrins.