Functional properties of a spray-dried porcine red blood cell fraction treated by high hydrostatic pressure

The aims of this study were to evaluate the functional properties of a spray-dried porcine red blood cell fraction (RBC), and the effects of the prior application of high hydrostatic pressure (HHP) on RBC protein functionality (solubility, foaming capacity, foam stability, water-holding capacity and texture properties of heat-induced gels) as well as on its microbiological quality and colour. The application of HHP (400 MPa, 15 min, 20 °C) and later dehydration allowed a dried product to be obtained with a reduction in the mesophilic bacterial counts of 3.2 logarithmic units. The colours of the pressurized and non-pressurized spray-dried RBC were the same, which indicated that both samples presented the same susceptibility to the hem group oxidation provoked by dehydration. The application of HHP increased the denaturant effects of spray-drying on hemoglobin (Hb), especially at pH 7 (isoelectric point; pI) since, after both processes, a decrease in protein solubility at neutral pH was observed. Spray-dried RBC had a maximum foaming capacity at the pI of Hb. The application of HHP decreased the foaming capacity but did not negatively affect the foam stability. Thermal treatment of RBC solutions led to hard and consistent gels at pH 7 whereas, at acid pH, less consistent, more adhesive and more elastic pastes were formed. The latter had higher water-holding capacities than gels at pH 7, in which, the water was retained by capillarity. Neither springiness and adhesiveness nor water-holding capacities of heat-induced gels or pastes were affected by the application of the HHP treatment to the fresh RBC.