Given the different nature of the heating processes that take place under conventional and microwave modes, the temperature control should not be limited to the initial and the final point of the process, but the whole temperature history of the product should
be taken into account. In this context, the PU parameter offers the possibility of evaluating the complete thermal load of the heating process at any reference temperature, as if it had taken place under isothermal conditions. This implies that the product is considered to reach the reference temperature instantaneously (Matsui et al., 2008), so the effect of processing factors that could be causing differences in the nature of the heat transfer, such as (i) product characteristics including consistency, solid/liquid ratio and thermophysical properties, (ii) sample quantity, and (iii) container type, size, and shape (Awuah et al., 2007), is avoided.
Given the different nature of the heating processes that take place under conventional and microwave modes, the temperature control should not be limited to the initial and the final point of the process, but the whole temperature history of the product shouldbe taken into account. In this context, the PU parameter offers the possibility of evaluating the complete thermal load of the heating process at any reference temperature, as if it had taken place under isothermal conditions. This implies that the product is considered to reach the reference temperature instantaneously (Matsui et al., 2008), so the effect of processing factors that could be causing differences in the nature of the heat transfer, such as (i) product characteristics including consistency, solid/liquid ratio and thermophysical properties, (ii) sample quantity, and (iii) container type, size, and shape (Awuah et al., 2007), is avoided.
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