Mechanical α-relaxations and stickiness of milk solids/maltodextrin systems around glass transition

Abstract

Background: Stickiness correlates with changes in mechanical α-relaxation properties and often results from glass transition and plasticisation of amorphous food components. In this study, milk solids with maltodextrins with different dextrose equivalents (DE9 and DE17) were analysed for glass transition (Tg), α-relaxation (Tα) and sticky point (SPT) temperatures using differential scanning calorimetry, dynamic mechanical analysis and a sticky point test respectively. Results: At the same maltodextrin contents, Tg and Tα were lower for milk solids with the higher-DE maltodextrin. Increasing maltodextrin contents gave Tg, Tα and SPT at higher temperatures, and the magnitudes of α-relaxations with high maltodextrin (DE9 and DE17) contents were less pronounced. Conclusion: Stickiness was governed by glass transition and affected by skim milk/maltodextrin composition. Stickiness was reduced with increasing maltodextrin content as a result of maltodextrin miscibility with skim milk solids, particularly lactose, which changed the relaxation behaviour above the glass transition. The mixes of milk solids with low-DE maltodextrin may show improved dehydration characteristics and powder stability resulting from increased Tg, Tα and SPT. © 2011 Society of Chemical Industry.