首页|Effect of cellulose powder content on the water sorption, glass transition, mechanical relaxation, and caking of freeze-dried carbohydrate blend and food powders
Effect of cellulose powder content on the water sorption, glass transition, mechanical relaxation, and caking of freeze-dried carbohydrate blend and food powders
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NSTL
Elsevier
The effects of cellulose powder and water activity (a(w)) on the equilibrium water content, glass transition temperature (T-g), mechanical relaxation, and caking of freeze-dried amorphous carbohydrate blend powders (dextrin-glucose mixture) were investigated. Water sorption isotherm and T-g-curve were obtained, and critical water activity (a(wc)) was determined as the a(w) at T-g = 25 degrees C. There was a minor effect of cellulose powder on the a(wc). The degree of caking was negligible below the a(wc) (glassy state), but increased remarkably above the a(wc) (rubbery state). Cellulose powder played a dispersive role in the powder, and thus diminished the degree of caking. The caking behavior could be described by a stretched exponential function, and an experimental formula to predict the degree of caking as a function of a(w)/a(wc) was obtained. The results for a food powder, with a more complex composition, largely deviated from the formula. Mechanical relaxation was evaluated as a force-reduction during isothermal compression. It was found that the relationship between the degree of caking and force-reduction could be described as a linear function independent of a(w) and cellulose powder content. The results for the food powder partially followed the linear relationship.
NSTL
Elsevier
