Submitted to: Meeting Abstract
Publication Type: Abstract Only
Publication Acceptance Date: 12/15/2004
Publication Date: 3/9/2005
Citation: Nalesnik, C.A., Onwulata, C.I. 2005. Drying kinetics of extruded dairy proteins. (abstract). AOCS Ann. Mtg. & Expo. Paper No. 53. Interpretive Summary: n/a
Technical Abstract: Extruded dairy proteins can be incorporated into various foods to provide added nutritional value. An important part of processing extruded dairy proteins is drying to a low-moisture content of 10%-15% w.b. to facilitate operations such as milling and blending. The drying kinetics of extruded dairy proteins are described. In this study, whey protein concentrate (WPC) and whey protein isolate (WPI) were extruded with a ZSK-30 twin-screw extruder at a melt temperature of 55-60 deg C and dried in a convection oven at 70 deg C. The two materials dried similarly with the extruded WPC drying from a moisture content of about 30% to 15% w.b. in 162 minutes, and the extruded WPI drying from a moisture content of about 34% to 15% w.b. in 156 minutes. The drying curves lie in the second falling-rate period which indicates that internal moisture movement is the rate limiting mechanism. A simple exponential model and Page model fit the drying curves well, with an R2 of 0.99. The drying rates of extruded WPC and extruded WPI decreased from 1.0x10-4 and 1.3x10-4 kg/(kg dry matter*s) to 1.4x10-5 and 1.9x10-5 kg/(kg dry matter*s), respectively. The drying kinetics data provide baseline drying rates of extruded WPC and extruded WPI with which to evaluate and optimize large-scale dryer performance.