Production of skim milk powder by spray-drying from transglutaminase treated milk concentrates: Effects on physicochemical, powder flow, thermal and microstructural characteristics

The effects of transglutaminase (TGase) treatment of skim milk concentrates on physicochemical, powder flow, thermal, microstructural characteristics and protein profiles of skim milk powders (SMP) were investigated. Spray-dried SMP samples produced from milk concentrates were TGase-treated at enzyme concentrations of 0 (control), 0.020% (TG-20), 0.030% (TG-30) and 0.035% (TG-35). Lower particle size values were observed in TGase-treated samples. TGase treatment slightly decreased zeta potential and increased the a* value (redness) of SMPs. Up to a concentration of 0.030%, TGase treatment decreased caking characteristics and increased glass transition temperatures of samples. The TGase treatment above 0.035% significantly decreased cohesion index and compaction coefficient at different speeds. TG-35 showed free flowing flow behaviour depending on the cohesion index, whereas control, TG-20, and TG-30 showed easy flowing behaviour. SDS-PAGE analysis revealed that high molecular mass bands indicated cross-linking in TGase-treated milk powders.