A cold shock for food: liquid nitrogen facilitates homogenisation
What do gummy bears, tuna fish and broccoli have in common? Foods like these cannot be homogenised for the BfR MEAL Study without prior treatment. This is why the study team cools them down up to minus 196 degrees Celsius within a very short space of time using liquid nitrogen. The benefit: the samples can be processed into a homogeneous mass without changing the levels of substances contained within.
Liquid nitrogen is used on foods difficult to process into a uniform mass at room temperature without leaving any pieces due to their texture. Such textures are, for example, gummy bears and freshly baked bread.
A certain level of heat is generated during homogenisation in a mixer. Liquid nitrogen is therefore also used when food cannot be heated artificially as it could influence the research results. For the process contamination module for instance, the study team are investigating the different levels of acrylamide in tuna. Because acrylamide can be broken down through intensive heating, tuna is cooled down using liquid nitrogen before homogenisation.
A third use of liquid nitrogen in the BfR MEAL kitchen concerns food being tested for its vitamin content. Vitamins can be highly unstable and react sensitively to heat and air. Food is also treated with liquid nitrogen to be able to homogenise food containing vitamins after being prepared for a meal without changing the vitamin content. The BfR MEAL study team specifically carried out a preliminary study using vitamin E as an example in order to investigate the best way of homogenising and storing nutrient samples. Accordingly, treatment with liquid nitrogen combined with storage for no longer than seven days is the gentlest and most practical method of minimising vitamin loss compared to freshly prepared food.