Yeasts and molds are a major problem in the storage, processing and marketing of mushrooms, even if grown and stored inside a carefully controlled environment and conditions. These pathogens can easily spread bacterial diseases through the crop and generate high product loss. STALAM has combined its expertise in the pasteurisation of packaged fresh food products and in the disinfestation of dry agricultural commodities to develop the first Radio Frequency (RF) unit specifically designed for the pasteurisation of dried mushrooms in bulk.
In the STALAM RF pasteurisation system the microbial and enzymatic inactivation is achieved by means of a gentle dielectric heating treatment which combines synergistically thermal and cell membrane electroporation effects. This dual action of the RF field is lethal for the biological entities contaminating the food substrate, thus providing a valuable sanitation and shelf-life extension technique. Significant microbe load reductions can thus be achieved without using chemical preservatives or applying drastic thermal treatments which would have detrimental effects on the physical and sensorial characteristics (especially the flavour) of the product. The treatment consists in a rapid exposure of the mushrooms to an electromagnetic field generated between a couple of electrodes inverting their polarity at 27.12 MHz frequency, inside a temperature-controlled process tunnel. The tunnel temperature, the RF voltage between electrodes and the speed of the belt carrying the mushrooms between the electrodes are the process parameters to be set according to the microbial inactivation level required.
The treatment ensures that the product is brought quickly and uniformly to temperatures necessary for the required level of microbial inactivation, but not so high to alter the mushrooms taste and flavour. The entire pasteurisation process takes just a few minutes.