desorption and adsorption curves, as has been shown for rigid
porous materials, say minerals. However, such hysteresis is
generally observed in the region of high aw, quite unlike that
shown in Figure 8.4. In most foods the pores would not be rigid,
and the negative capillary pressure would cause them to become
closed, strongly altering the sorption isotherms. Possible relations
between the presence of non rigid pores and sorption hysteresis are
currently far from clear.Question
To a solution of sucrose in water, mole fraction 0.05, 5%of a protein is added. The
protein dissolves, it has a molar mass of 20 kDa, and it contains just sufficient Naþto
neutralize the net 10 negative charges per molecule. To what extent will the addition
of protein change the water activity of the solution?
FIGURE8.8 Amount of water held by myofibrillar muscle protein as a function of
pH at low ionic strength. The broken line indicates bound water.