Question 1
In what direction will the water activity of a liquid food change (higher, lower, or
virtually unaltered) if the following changes occur, keeping other factors constant?
- Addition of sodium chloride
- Addition of native starch (granules)
- Heating the food with starch and cooling again to the original temperature
without loss of water - Enzymatic hydrolysis of the protein present
- Emulsifying oil into it
- Freezing part of the water
What is the explanation in each case?
FIGURE8.2 Approximate water activityðawÞof some foods versus mass fraction of
waterðwÞ.