September 23, 2015

23/09/2015: Heat treatment: precision fumigation with benefits

by Vasilis Sotiroudas, Food Scientist, Heat Treatment specialist, Agrospecom, Greece 

First published in Milling and Grain, June 2015 

Use of Methyl Bromide (MeBr) has been banned in most developed countries since 2007. From January 1, 2015, it is not available anywhere as a fumigant for flourmills and other industries. Several fumigation alternatives have been tried around the world with heat treatment being one of them. But how good are these compared to good old MeBr? Can such alternatives be used for precise fumigation, i.e. a tightly controlled and monitored fumigation process?  Methyl Bromide has been a good fumigant, but not excellent since the main disadvantage of gas fumigants is that they need airtight buildings. And in the real world, very few buildings are made airtight or can become airtight with proper sealing work. The majority of buildings will never hold the gas, especially on a windy day or when there are significant temperature differences between day and night.

The heat advantage
Heat treatment has been practiced worldwide for a few years and is by now deemed a very effective replacement of MeBr for structural fumigation. Insects die at temperatures above 50oC because the proteins in their bodies coagulate, their salt equilibrium becomes damaged and they dry out. All insect stages are affected and no resistance to heat has been observed in the lab or in the field. Electricity, gas, petrol and steam can be used to generate heat for insect extermination. In our work, we have found out that each type of heater has its pluses and minuses.

Electrical heaters are easy to use, easy to handle and efficient; but they cannot be used to treat an empty concrete silo (you need a gas heater for that, with a long ductwork). Gas heaters need to be placed outside the building, so for high buildings you may need to lift heaters by crane to the top floor. In most of the cases, the use of special air ducts through available shafts enables us to treat several floors and sections of a mill at the same time. In comparing recycling of air (electrical heaters placed inside the building) with introduction of new air (gas heaters placed outside), we found out that the increase of pressure in the latter case helps the hot air to enter cracks and crevices. In practice, the merits of electrical and gas heaters can be combined, using both types to treat large mills with speed and efficiency.                   

Read the full article in Milling and Grain HERE.

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