- Oct 2021
A simplified freezing point depression (FPD) equation was derived for calculating water activity (aw) of food systems. The aw values as calculated by FPD data agreed with literature data for a variety of foods to within ± 0.01 aw units. The FPD equation was found particularly useful for calculating aw values of frozen foods at temperatures between 273.1.5–233.15 °K (0 to −40°C).
± 0.01 aw? That's crazy accurate. Temperature is extremely easy to measure at home, which makes this a perfect technique for home food preservation. In particular, it can be used with sugar-free, salt-free, and other obscure recipes for which water activity is hard to estimate.
Additionally, this accuracy could be run in reverse. Knowing the water activity of ice-cream can tell you the freezing point. Moreover, a mini fridge could keep select food items chilled below 0°C for better preservation. In particular, I plan to dissolve erythritol into unsweetened plant milks and lower my fridge temp accordingly.