where n is surface unit normal vector, subscripts o and i refer to the outside and inside of the resistive layer, respectively. Here, k is the thermal conductivity of the packaging material in W/(m•K) and d is the thickness of the packaging material in m. Individual beefsteaks, peppers & onions packs, French toast and one side of Danishes box were packed in expanded polystyrene (EPS). All the other boxes and concentrated orange juice cartons were made of cardboard. The thermal conductivity of EPS was specified to be 0.04 W/(m•K) and that of the cardboard box was 0.065 W/(m•K) ( Kumar & Subhendu, 2009). The thicknesses of all the packaging materials were in the range of 0.5 mm to 1 cm.