Measuring antifreeze protein activity

Abstract

In this chapter an overview of the most commonly used techniques in both quantitative and qualitative antifreeze protein (AFP) research is presented. This includes, among others, thermal hysteresis measurement by nanoliter cryoscopy, ice recrystallization inhibition assay by microscopy and immunolocalization. AFP research has come a long way, from merely observing the effects of AFP to explaining some of the fundamental mechanisms of action. These involve a dynamic hydration shell around proteins, the nanometer curvature of ice crystals in the presence of AFP, and the flux of water molecules between ice crystals as they recrystallize. The interest in AFP as an additive to food has always been high, and a wealth of methods have been applied to foods with added AFP. Most of these are not concerned with the function of AFP, but rather the effect on a complex matrix, such as meat or dough. Some of these indirect methods for detecting the effects of AFP are also presented at the end of the chapter.