Redistribution of Protein Biological Activity in a Freeze-Dried Cake

• Published in: Drying technology Vol. 31; no. 1; pp. 102 - 111
• Main Authors: Nakagawa, Kyuya, Murakami, Wataru, Hatanaka, Takanobu
• Format: Journal Article
• Language: English
• Published: Philadelphia Taylor & Francis Group 01.01.2013; Taylor & Francis Ltd
• Subjects: Baked goods; Biological; Biological activity; Cakes; Concentration gradient; Drying; Enzymes; Food preservation; Freeze drying; Freezing; Pharmaceuticals; Polysaccharides; Proteins; Redistribution
• ISSN: 0737-3937; 1532-2300
• DOI: 10.1080/07373937.2012.723291

Lactate dehydrogenase (LDH) solutions were freeze dried in order to investigate the redistribution of the remaining LDH activity in the dried cake. D-Mannitol and a polysaccharide (κ-carrageenan, ι-carrageenan, or dextran) were mixed and used as stabilizers in freeze drying. It was found that the remaining LDH activity was significantly redistributed in the freeze-dried cake, and the enzyme concentration was not uniform along the axis of the dried cake due to variations in the freeze-drying conditions and stabilizer concentration. In some cases, active enzymes were highly localized in a specific portion of the dried cake. This was mainly due to the redistribution of the protein content. Further freeze-drying tests employing bovine serum albumin (BSA) and the above-mentioned polysaccharides showed that proteins (BSA) tended to accumulate in the lower portions of the dried cake, forming concentration gradients. Therefore, the concentration gradient in the freeze-dried cake was mainly due to the freezing process. This redistribution of protein content contributed considerably to the apparent redistribution of enzyme activity. The results suggest that a process that can control the redistribution of protein content in a freeze-dried cake would further improve the biological activity of freeze-dried proteins.