51A-14

C. A. MIRELES DEWITT and M. T. Morrissey. Food Science/OSU Seafood Laboratory, Oregon State University, 2001 Marine Drive, Astoria, OR 97103

JUSTIFICATION: Pacific Whiting (Merluccius productus) is a ubiquitous groundfish off the Northwest coast of Oregon. Its abundance has resulted in a dynamic onshore surimi processing industry. Research has shown that Pacific Whiting contains an abnormally high level of proteases (specifically cathepsin L). Significant reduction of these proteases is normally achieved by washing. We hypothesized that pilot plant recovery of these valuable, bioactive components from the processing wash water could be achieved.

OBJECTIVES: To recover proteases from processing wash water using pilot plant scale equipment.

METHODS: Information for optimized recovery was obtained from previous lab scale experiments. Processing wash water was collected, pH adjusted, and heat-treated. Treated wash water was centrifuged to separate insoluble/soluble proteins. Supernatant was collected and concentrated with ultrafiltration. Analysis included activity measurements, active site titration, SDS-PAGE, activity staining, and proximate analysis. Calculations were made to determine purity-fold and yield. Stability of the frozen and freeze-dried protease was monitored for 10 weeks. Recovered protease activity was compared to that of commercial papain.

RESULTS: Flux was doubled as a result of wash water treatment. Cathepsin L activity was predominant. SDS-Page identified significant reduction of 55 - 200 kD proteins. Two bands of significance remained at 36 and 50 kD. Cathepsin L has been associated with the former. Enzyme purity was increased ~100-fold and yield was about 80%. Stability (frozen and freeze-dried protease) was maintained for 9 weeks at -15°C. Freeze-dried preparations were also stable for 9 weeks at refrigeration temperatures. The activity of commercial papain was approximately 30x greater than the recovered protease at pH=5.5 and 30°C.

SIGNIFICANCE: A simple, effective method was developed for the simultaneous reduction of total proteinaceous material (i.e. purification) and recovery of a stabile crude protease fraction from surimi wash water.