Fraunhofer UMSICHT scientists have developed a new process to kill off germs in dry foods such as almonds.
The new process uses compressed CO2 to decontaminate food and it could save manufacturers from pulling off food products from store shelves as was done previously.
Processing affects the quality of food – particularly that of plant-based products that are consumed raw. They may be contaminated with harmful bacteria like salmonella, a leading cause of food poisoning.
These bacteria can even spread to dry foods which experts call ‘products with low water activity’. This group of low-moisture foods includes almonds, nuts, dried fruits, spices, milk powder and even tea.
According UMSICHT scientist Karen Fuchs, salmonella can go dormant to survive on almonds. In the process, they produce additional biomass that protects them from desiccation.
If water enters the picture, salmonella then proliferate explosively. But it takes just ten to one hundred of these bacteria to cause food poisoning.
Contaminated almonds that make their way into production facilities after harvesting can also contaminate other batches, says Fuchs.
Now Fuchs’ team along with researchers University of Alberta in Canada are testing the use of CO2 in decontaminating affected almonds.
The plus point of using this method is that it is not harmful to the environment or health and can be separated from almonds without a trace of residuals. This does not involve any energy-intensive steps for purification.
As part of their study, the scientists decontaminated and impregnated almonds with antimicrobial oils using compressed carbon dioxide in a high-pressure autoclave.
The oil extract coats the almond, making it difficult for germs to recontaminate the fruit. The advantage of this process is that almonds retain their characteristic flavor and quality.
Fuchs and her team carried out tests with Staphylococcus carnosus, a surrogate organism known for an even more resistant reaction than salmonella, proving that the process in the autoclave does not adversely affect the shelf life, rancidity or lipid composition of almonds.
According to Fuchs, this process could also benefit other foods. The increased lipid oxidation potential is especially useful for any food that is prone to oxidation.
Image and content: Karen Fuchs/Fraunhofer UMSICHT