The physical properties of commercial starch hydrolyzate (varying in dextro
se equivalent values, DE, from 0.5 to 42) solutions in the frozen state wer
e related to their composition. At 20% (w/v) hydrolyzate concentration, an
inverse linear relationship between DE and apparent glass transition temper
ature (T-g') of the unfrozen solute matrix was observed. The T-g' temperatu
res remained relatively constant for solute concentrations below 40% (w/v);
above this concentration the T-g' was depressed, possibly due to the plast
icizing effect of additional water entrapped in the glassy state during non
-equilibrium freezing. Simple predictive models (based on the Flory-Fox equ
ation; 1/T-g = Sigma{w(i)/T-gi}) were found to predict reasonably well the
T-g' value of 'binary' monodisperse and polydisperse hydrolyzate mixtures o
f varying proportions between the two components. Linear relationships were
also found between T-g'(measured) (by calorimetry) and T-g'(predicted) (ba
sed on the Flory-Fox model, and using the oligosaccharide composition of th
e hydrolyzates and the respective T-g' values of the pure components). The
rate of oxidation of ascorbic acid has been measured in the presence of sta
rch hydrolyzates at temperatures between -4 and -16 degrees C. Both the Arr
henius and WLF (Williams-Landel-Ferry) kinetic models were found to describ
e the temperature dependence of reaction rate constants reasonably well. Ho
wever, knowing the T-g' value of the amorphous maltodextrin was not suffici
ent to predict its cryostabilization behavior. (C) 1999 Elsevier Science Lt
d. All rights reserved.