Evaluation of Process Conditions for Ultrasonic Spray Freeze Drying of Transglutaminase
Tokat Gaziosmanpasa University, Faculty of Engineering and Architecture, Food Engineering Department, Tasliciftlik Campus, 60150 Tokat, Turkey
Received: 16 October 2019
Accepted: 11 March 2020
spray freeze drying, ultrasonication, transglutaminase, enzyme activity, flow behaviour, particle morphology
In this study, a commercial transglutaminase enzyme was dried using an ultrasonicspray freeze drying method and the effects of the process conditions were optimized tomaximize the final transglutaminase activity. Accordingly, process parameters affectingenzyme activity were selected, such as nozzle frequency (48 and 120 kHz), flow rate (2, 5and 8 mL/min) and plate temperature for secondary drying (25, 35 and 45 °C). Moreover,the effects of different pH values (pH=2.0 and 9.0) and high temperature (80 °C) on enzymeactivity, physical properties and particle morphology of transglutaminase were discussed.According to the results, transglutaminase preserved its activity despite ultrasonic sprayfreeze drying. Sonication enhanced the enzyme activity. Using the desirability functionmethod, the optimum process conditions were determined to be flow rate 3.10 mL/min,plate temperature 45 °C and nozzle frequency 120 kHz. The predicted activity ratio was1.17, and experimentally obtained ratio was 1.14±0.02. Furthermore, enzyme produced byultrasonic spray freeze drying had low moisture values (2.92-4.36 %) at 8 h of drying. Whenthe morphological structure of the transglutaminase particles produced by ultrasonicspray freeze drying under the optimum conditions was examined, spherical particles withpores on their surfaces were observed. In addition, flow properties of the transglutaminasepowders were considered as fair under most conditions according to the Carr index.
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