Freezing time formulas for foods with low moisture content, low freezing point and for cryogenic freezing

摘要

Existing food freezing time formulas have not been tested on low moisture, low freezing point foods or cryogenic temperatures. A systematic numerical experiment was therefore performed to generate freezing times over a wide range of parameters, never before covered in the literature, yet still within industrial practice. The results were used to evaluate four well-known freezing time formulas. Pham's first (three-stage) method has the best theoretical basis and fewest empirical parameters, and agrees best with numerical predictions. By applying simple correction factors, this method agrees with numerical predictions to within ±10% while Pham's second (two-stage) method is almost as accurate. For the freezing time of fresh foods (T_f ≥ -1.5 ℃), Pham's first method can be used without modification. The corrected formulas remain accurate under cryogenic freezing conditions.