SELECTED CHARACTERISTICS of EXTRUDED BLENDS of MILK PROTEIN RAFFINATE OR NONFAT DRY MILK WITH CORN FLOUR

Abstract

Various levels of milk protein raffinates (MPR) containing different concentrations of lactose and nonfat dry milk powders (NFDM) were co-extruded with corn flour. the extrusion experiments were performed on a twin-screw extruder at 100°C, 125°C and 150°C (last section temperature). Differential scanning calorimetry (DSC) results indicated that the starch in extrudates was completely gelatinized. Lower processing temperatures resulted in decreased browning, while the level of lactose in the raffinates did not appear to cause a significant difference in product browning. Extrudate expansion ratio decreased at levels higher than 5% NFDM or MPR. Also, as the MPR content increased, to a certain level, the breaking strength of extrudates increased and beyond that the trend was reversed. the level and type of milk protein incorporated and extrusion temperature also affected the water holding capacity, nitrogen solubility index and sorption characteristics of extruded samples. In general, milk proteins appeared to improve the textural properties of the extrudates when used at levels below 5%.