Effects of cooling rate, annealing time and biological antifreeze concentration on thermal hysteresis reading.

Thermal hysteresis (TH) readings depend on the cooling rate, annealing time and the concentration of the biological antifreeze (AF) (i.e., antifreeze protein or antifreeze glycoprotein). Such time- and concentration-dependent TH readings are not true (or absolute) values. The true TH should be independent of time and AF concentration, and it should be a unique value for a given AF. Only the true TH can be used to assess the activity of an AF. A mathematical model is proposed to explain the time- and concentration-dependent behavior of AFs. The model assumes a reversible Langmuir adsorption mechanism for the AF molecules and the Kelvin effect to be applicable. A TH equation that correlates the TH reading with the cooling rate, annealing time and AF concentration was derived. The time-dependent behavior was attributed to the slow adsorption process of the AF. The theoretical calculations were compared with previously published data on the effects of the cooling rate, annealing time and AF concentration on TH readings. The calculated results agree qualitatively with the literature data. The experimental methodology required for obtaining the true TH of an AF is suggested.