Determination of thermo-physical properties of freeze-dried foodstuffs

Abstract

The thermo-physical properties of some important foodstuffs have been estimated and are correlated with temperature and pressure using semi-empirical technique. For determination of thermal conductivities (k) of paneer and mango samples, ‘Uniformly Retreating Ice Front’ (URIF) model has been used at two different methods of freezing conditions i.e. conventional slow freezing and rapid cryogenic freezing. In all the cases, linear equation expressing <i style="">k</i> as dependent variable with chamber pressure (<i style="">P</i>) [ranging from 0.003 to 0.05 mbar]<b style=""> </b>and average temperature of dried layer (<i style="">T</i>) [ranging from 275 to 295 K] as independent variables has been established. The heat capacity, <i style="">C</i>_p of different freeze-dried foodstuffs have been determined experimentally using ‘Differential Scanning Calorimeter’ for a wide range of temperature at specific values of moisture content of practical significance. The equations of the best fit curves are also presented, enabling one to estimate the heat capacity value for freeze dried foodstuff (with specified moisture content) at any temperature within the range of 258 to 319 K.