Freeze-drying and Protein Denaturation in Muscle Tissue; Losses in Protein Solubility

Abstract

IN the course of a search for possible relationships between the freeze-drying procedure and the subsequent extractability of proteins from the freeze-dried tissue, it was found that freeze-drying of ox muscle does not necessarily reduce the extractability of the component proteins separable by Helander's procedure¹ which employs, in sequence, 0.03 molar phosphate buffer and 1.1 molar potassium iodide. These findings were, in part, a confirmation of the work of Cole and Smithies² and of Connell³ and support the thesis that freeze-drying need not cause irreversible denaturation of the proteins present. Furthermore, our results explain the observations of those workers who, in experiments in which the effects of dehydration and of high temperature were combined, found that rapid freeze-drying lowers the extractability of proteins⁴. Thinking that the losses in extractability reported might be caused by the high temperature generally used to accelerate freeze-drying, we tried to separate the effects of freeze-drying from those of high temperature. We were thus able to show that heat applied during the course of freeze-drying to accelerate dehydration may induce insolubility in the portion already dried, while the part still to be dried remains undamaged.