Why microwaves

Viscous substances, such as the nutrient medium, containing agar and plenty of sugar, are media exceptionally difficult to heat using standard solutions applied in thermal sterilization, such as heaters or heat exchangers. That is because those technologies require a big temperature gradient between the walls (which are hot) and the cooler medium. In such conditions, it is practically unavoidable that some components settle on the walls, and decompose in high temperature, which speeds up further sedimentation of material on the more and more porous surface (covered with deposit);as the deposit is a good insulator, the heating elements become overheated (which speeds up component decomposition even further), and thermal capacity of the heat exchanger or heater decreases at the same time. Therefore, a deterioration of the parameters of the sterilized medium is unavoidable, and what is worse, it is difficult to define exactly what, and how much of it decomposed. 

Microwaves appear to be an ideal solution to avoid the above problems. Using them, energy is delivered directly to the flowing liquid, evenly in the whole volume, in a way heating each of its molecules separately. The equipment walls do not heat up then (the teflon they are made of is transparent to microwaves) - except for the secondary effect of the hot liquid. Due to that, sedimentation or decomposition of components is not induced. It is also of importance that pure PTFE (Teflon) is characterized by the lowest possible adhesion factor - many times lower than polished stainless steel, thanks to which the heating chamber inside remains always clean, and all it needs is flushing.