Cross-polarization/magic angle spinning NMR to study glucose mobility in a model intermediate-moisture food system.
Theories for the chemical stability of foods cite the role of moisture content or water activity in reactant mobility, though mobility has been variously defined. One theory, based on plasticization by moisture, is limited by a lack of research directly linking the mobility of a matrix to the mobility and reactivity of small solute molecules in foods. A cross-polarization/magic angle spinning technique was developed to study glucose rotational mobility in the solid state over a range of water activities and in matrixes with different glass transition temperatures. Data analysis stressed the significance of separating molecular mobility from relaxation time. Results showed that, in a caseinate matrix, compared to a control, adding glycerol yielded the highest glucose mobility and lowest glass transition temperature (T(g)), while adding sorbitol also increased mobility and lowered T(g). Consequently, plasticization by either moisture or these humectants increases the mobility of small solute molecules such as glucose.
Sherwin
Craig P
CP
Department of Food Science, University of Wisconsin, 1605 Linden Drive, Madison, Wisconsin 53706, USA. cpsherwin@wisc.edu
Labuza
Theodore P
TP
McCormick
Alon
A
Chen
Bin
B
D055598:Chemical Phenomena; D002627:Chemistry, Physical; D005524:Food Technology; D005898:Glass; D005947:Glucose / Q000737:chemistry*; D005990:Glycerol / Q000008:administration & dosage; D009682:Magnetic Resonance Spectroscopy / Q000379:methods*; D008962:Models, Theoretical; D013012:Sorbitol / Q000008:administration & dosage; D013696:Temperature; D014867:Water
D014867:Water; D013012:Sorbitol; D005947:Glucose; D005990:Glycerol