1st Nordic Drying Conference - NDC'01, Trondheim, Norway, June 27-29, 2001

HEAT PUMP DRYING OF COD PROTEIN ISOLATES 1 Odilio Alves-Filho, 1 Trygve Eikevik, 1 Ingvald Strømmen, 2 Stephen D. Kelleher, 2 Yuming Feng and 2 Herbert O. Hultin. 1 Center for Dewatering R&D, SINTEF Energy Research, Trondheim, Norway E-mail: odilio.alves@energy.sintef.no 2 Advanced Protein Technologies, Inc. North Main Street, Ipswich, MA 0938, USA E-mail: hultin@tiac.net Keywords: Acid, gel, muscle, powder, reconstitution, solubilization. ABSTRACT Dried samples of protein isolated from cod have been produced at SINTEF and NTNU using heat pump drying technology. An adiabatic heat pump dryer operating at low temperature and at atmospheric pressure is suitable for processing cod protein as well as other heat sensitive materials. The protein isolates samples were prepared from cod by solubilization and centrifugation to remove membranes. The muscle proteins were precipitated by adjusting the pH to 5.5 and the protein isolate was collected by centrifugation. The isolate was adjusted to pH 7.5, 6.4 or kept at 5.5 prior to freezing. The frozen samples were granulated to appropriate size dried in the lab scale adiabatic heat pump dryer. The dryer operates at low temperature and at atmospheric pressure and has drying and heat pump closed circuits. The dried protein samples were reconstituted with water and a cryoprotectant mixture to reach a pH of 7.5. The mixture was heated to produce gels for pH and gel strength measurements. The dried protein with different pH values presented gel with variable strength and the strength approaches the strength of vacuum-freeze sample prepared with pH 5.5. This paper describes the adiabatic heat pump drying of protein isolate from cod. The goals were to identify the preparation procedures, to establish the drying conditions and to measure the relevant powder characteristics. The results indicate that the heat pump technology is suitable to produce dried protein isolates with at least three controllable properties including the gel strength, the color and bulk density. The future tests will be done in a newly built carbon dioxide heat pump dryer, which operates with higher COPs than usual processes and is an environmentally friendly technology.

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