1. Explain in detail how glass transition temperature and molecular mobility relate to the following:

      Stable drying process

      Stable freezing process

      Stable freeze drying process

2. Nonfat dried milk is produced by spray-drying skim milk. During dehydration, the water activity (Aw) was monitored as mositure was removed. The graph shown below contains isotherms for dehydration of teh skimmilk, rehydration of teh nonfat dry milk as well as an isotherm for another food (confectionary product) containing large levels of sugar.

a.) Identify the isotherm that you would expect to obtain during skim milk dehydration. Provide reason for your answer (use the graph below)

b.) Divide the isotherm you have chosen (in a) into regions based on the type of water removed from skimmilk while undergoing dehydration to produce nonfat dry milk. Identify the various types of water repsented in each region.

c.) The isotherms shown above were obtained at 25C. Show (Graphically) the effect that determining water activity at 40C would have on the desorption isotherm obtained for the production of nonfat dry milk. Provide reason for your answer.

** x axis = water activity