Spectroscopic Approaches to the Understanding of Water in Foods

Abstract

This chapter reviews NMR and dielectric studies of hydration. It concentrates mainly on protein hydration as a model for foodstuffs. The relevant areas of theory are discussed and illustrative results from the literature are given. It is concluded that the notion of “bound water,” in the context of food systems where there is an excess of water, is not useful one. The dynamic perturbation of water by biopolymers is very small and cannot be used to account for properties such as water holding. Effects of biopolymers on such features as the freezing of water and vapour pressure are entirely consistent with normal thermodynamic behaviour and need no special explanation. There is clear evidence that when proteins reach an approximate water-to-protein ratio of about 0.3 to 1, there is a transition in behaviour. This is reflected across very wide range of measurements, and it seems to be associated with a point where the effects of water on the internal protein dynamics cease.

Keywords:

• water
• hydration
• NMR
• dielectrics
• non–freezing water
• protein