Effect of food structure on the distribution and reactivity of small molecules

•Partitioning between phases can explain many effects of food structure on chemical reactivity.•The ‘polar paradox’ used to understand antioxidant behavior is based on partioning between two phases.•The newer cut-off effect theory typically requires partioning between three phases.•Other workers have proposed the interface can act as a diffusion barrier to reagents.

How food structure affects chemical reaction kinetics is one of the big, general problems in food science. We describe how the simple ideas of partitioning and diffusion have been developed to explain increasingly complex behaviors; especially cut-off effects of antioxidants in emulsions and barrier properties of the interface. Finally we consider some ways molecular distribution can be measured.