Correlation of microbial response in model food systems with physico-chemical and “mobility” descriptors of the media

The role played by water activity (aw), “mobility” (“molecular” by Nuclear Magnetic Resonance (NMR) analysis and “macromolecular”, by glassy to rubbery transition, thermal analysis) and physico-chemical properties of the media in modulating microbial response have been studied in multicomponent model food systems of different physical state. NMR “molecular” mobility correlated well with microbial (mold spore) response in solid and semisolid systems (dry and intermediate moisture foods) while in high moisture, liquid, homogeneous systems water activity was found to correlate better with Staphylococcus aureus activity. Correlation between microbial survival ability and glassy to rubbery transition in heterogeneous and complex model systems is not yet conclusive.