OUTLINE OF A SYSTEM FOR THE SELECTION OF THE OPTIMUM STERILIZATION PROCESS FOR CANNED FOODS .2. THE DETERMINATION OF HEAT-TRANSFER COEFFICIENTS AND HEAT CONDUCTIVITIES IN SOME INDUSTRIAL EQUIPMENTS FOR CANNED PRODUCTS

The effective heat conductivities in three kinds of baby foods and four kinds of canned meat products, were determined based on heat treatments. The heat transfer coefficients in the divided hydrostatic sterilizers: OHS 6 and OHS 750-26-U-M3-102 (made in Hungary) as well as in the horizontal retort Type LW 2002 (without rotations, manufactured by Lubeca, FRG), were also evaluated. Laboratory experiments were also carried out, where solid metal cylinders of the size of cans and cans filled with boiled egg-white were used. Results were obtained partly by numerical methods (KORMENDY, 1987) based on elementary heat balances, and partly by other, less known, methods or by the expedient combination of the two. The methods are based on the presumption that unsteady-state conditions of heat conduction exist within the canned product. In the course of calculation the thermophysical parameters were systematically varied to achieve between the measured and calculated temperatures the minimum of the mean (square) difference. Between the heat transmitting medium and the surface of the product the heat transfer coefficient is in the equipment Type OHS 6 alpha-R > 200, in the equipment Type OHS 750-26-U0-M3-102 alpha-R = 500 and in the horizontal autoclave Type LN 2002 alpha-R almost-equal-to 700 Wm-2 degrees-C-1. The apparent (effective) thermal conductivities varied in canned baby foods between 0.61 and 2.1, in canned meat products between 0.67 and 1.45 Wm-1 degrees-C-1. In the course of this study the authors took into account the possibility of the development of an optimum-seeking system, too (KORMENDY, 1987).