Water Plasticization and Crystallization of Lactose in Spray‐dried Lactose/Protein Mixtures

Abstract

ABSTRACT: Water plasticization led to depression of the glass transition causing significant changes in the physico‐chemical and crystallization properties in storage of lactose and lactose/protein (3:1) mixtures. Glass transition (Tg) and crystallization temperatures (Tcr) were determined using differential scanning calorimetry. Whey protein isolate (WPI), albumin, and gelatin increased the Tg of dry powders; when Na‐caseinate was used, a decrease was observed. In the presence of proteins and water, a decrease of Tg at aw ≤ 0.23 was observed. At aw ≤ 0.33, proteins increased the Tg In the anhydrous state, Tcr decreased in the presence of proteins possibly because of browning. WPI, Na‐caseinate, albumin, and gelatin delayed lactose crystallization in humidified samples, with albumin and gelatin delaying it more than WPI at all storage humidities. Temperature difference between an observed instant crystallization and glass transition (Tcr to Tg) was larger for humidified samples containing proteins than for lactose. Various proteins and water affect crystallization behavior of amorphous lactose differently in spray‐dried powders. This should be considered in evaluating sugar crystallization properties in food products including dairy powders.