Instant and physicochemical properties of agglomerated high-pressure jet spray-dried skim milk powder

Condensed skim milk was high-pressure jet processed at 100 and 500 MPa and spray dried to produce skim milk powder (SMP). The objective of this study was to improve both the instant and reconstituted physicochemical properties of high-pressure jet spray-dried SMP by introducing an agglomeration step during powder processing. Scanning electron microscopy images verified that effective agglomeration was achieved. Agglomeration with lecithin to SMP processed at 500 MPa improved the wettability time (>60 min to 4 min), sinkability (<1 mg/min.cm² to 73 mg/min.cm²), and dispersibility (34% to 58%) but not solubility, which remained at 77% (wt/vol). Agglomeration with lecithin to SMP processed at 500 MPa and reconstituted to 9% (wt/vol) reduced the viscosity (8 mPa.s to 6 mPa.s), G' maximum (45 Pa to 34 Pa), and total gelation time (2.6 h to 2 h). Agglomeration and lecithination of powders markedly hindered foamability but did not influence emulsifying activity, which was higher over time (>30 min) in reconstituted powders obtained from high-pressure jet processing at 500 MPa. The differences observed in instant and reconstituted physicochemical properties of high-pressure jet spray-dried SMP were attributed to the structural modifications of proteins during processing and their subsequent interactions with lecithin.