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High-pressure for Dry Product Decontamination - First Findings

http://www.bulletins-electroniques.com/actualites/64025.htm

Decontaminating dry products, such as spices or dry herbs that are usually delivered as powders, is a requisite. However, there is no actual efficient solution. Currently used thermal systems can get rid of 99% of the microorganisms but do not destroy the sporulated forms. This is why Spiceclean is important. The project, which is accredited by the Vitagora competitive cluster and funded by ANR (French national research agency), will be evaluating the efficiency of two innovative athermal treatments, one using high pressure, the other pulsed light. As part of his doctoral thesis at AgroSup Dijon, under the dual supervision of Patrick Gervais and Jean-Marie Perrier-Cornet, Alexandre Colas, an AgroParis Tech graduate engineer, is involved in the project. His research addresses the impact of high gaseous pressure on bacteria spores, viruses and sewage fungus spores. The first mid-term findings are encouraging.

At the Food Microbiological Process Engineering Laboratory (GPMA, Génie des Procédés Microbiologiques Alimentaires) headed by Patrick Gervais and specialized in high-pressure, Alexandre Colas works mainly on two types of processes. One uses high pressure gas chambers, the other gas pockets placed in hydrostatic chambers, well-known equipment used in the fruit juice sector. "My work consists in testing both processes by changing different parameters, such as pressure, temperature, time, and the hydration of the microorganisms we're working on. We also vary the gas relief kinetics," he recapped. This is the technological side of his research that he is carrying out at the same time as the other side focused on understanding. The point is to try and understand what is the direct impact of the gases under pressure on microorganism structure, as it varies depending on the type of gas we use," explained the Ph.D. fellow. How the microorganisms under study can be inactivated still needs to be explained. Is permeabilization of the membranes involved or a denaturation due to the pressure of certain molecules, such as proteins?

At the mid-term of his research, Alexandre Colas has already found interesting results. Until now, he has been using nitrogen and CO2, but he has to see what results would come of a nitrogen-hydrogen mix. "Today we can inactivate nearly 99% of bacteria spores, a result that is virtually the same as the one pulsed light is used. However, it is still not enough for a sterilization treatment," he said. Pressure plays an important part. For instance, sewage fungus inactivation begins at 1,500 bar whereas bacteria spore inactivation requires over 4,000 bar. Hydration also plays an important role. "It turns out that the lower the hydration, the more inactivation is possible, an encouraging result because dry products have to be decontaminated." However, depending on the type of gas that is used, hydration has a greater or lesser impact on inactivation. "We have to optimize the emerging techniques."

"For the time being, we are within deadline," said Alexandre Colas. He still has to prove the efficiency of the studied treatment on vegetative forms that are not resistant, before transfer onto a matrix for later tests directly on the contaminated spices. "Then, we will have to check the results, given that factors may have an impact depending on the location of the microorganisms in the spices," he said. The three-year goal is to have a reliable process that could possibly be transferred to industry. However, to reach that goal, ideally the required pressure would have to be lowered to attain a reasonable level and affordable gases would have to be used; mixing several gases seem to be the most promising solution.

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AgroSup Dijon - Alexandre Colas - email: alexandrecolas@gmail.com

Code brève
ADIT : 64025

ADIT - Jean-François Desessard - email: jfd@adit.fr

eTech France numéro 244 (12/07/2010) - ADIT / ADIT - http://www.bulletins-electroniques.com/actualites/64025.htm