Model of Cryoprotectants Effect on Thermal Conductivity and Enthalpy of Surimi Prepared from Adriatic Pilchard

Dragan Kovačević, Želimir Kurtanjek

Faculty of Food Technology and Biotechnology, University of Zagreb, Pierottijeva 6, 10 000 Zagreb, Croatia

Article history:
Received January 28, 1997
Accepted June 13, 1997

Key words:
surimi, thermophysical properties, mathematical model, DTA, line heat source method

Summary:
Determination of relative apparent specific enthalpy (H), initial freezing temperature (θi, and thermal conductivity (k) of surimi in the temperature range from -25 °C to +5 °C by differential thermal analysis (DTA) and a system for measurement of thermal conductivity of food by the method of unsteady responses from a line heat source are presented. Samples of surimi were prepeared in laboratory conditions from Sardina pilchardus with addition of Polydexstrose, starch, and mixture of sorbitol and sucrose (S/S) in mass ratio 1:1. Water content in surimi was 82.01% before mixing with the added substances. For interpretation of experimental results and determination of thermophysical properties mathematical models of H(θ) and k(θ) were used, while θi were determined from DTA curves. Values of k, H and θi, of surimi samples were correlated with mass fractions of the added substances in the range of 0-12%. Values of H(θ) and k(θ) at freezing temperatures were dependent of a mass fraction of unfrozen water which resulted from various cryoprolectant efficiency of the added substances.