Neutron chefs

Nuclear scientists and food researchers will gather at the Reactor Institute Delft this weekend to discuss how neutrons can reveal the hidden properties of food.

Neutrons reveal food’s hidden properties. (Photo: Sam Rentmeester)

The crispy freshness of bread, the formation of yoghurt, the structure of cheese or the anatomy of candy bars. Such are the topics that will be discussed by the unusual amalgam of scientists and corporate researchers who will gather at the Neutrons and Food workshop held at the TU’s reactor institute, starting this weekend (Sunday 29 January to Wednesday 1 February). Co-organiser Dr Wim Bouwman (Applied Sciences) is excited that nine of the 55 participants are from industry (Mars, Unilever and Nestlé to name a few). “These people have practical questions. With our neutron facility, we may set up collective research programmes.” Bouwman organised the workshop together with food science expert, Professor Erik van der Linden, from Wageningen University.

It turns out neutrons are very well-suited for revealing new knowledge about food. For one, neutrons interact nicely with hydrogen atoms. In the food context, this provides a measure for the degree of saturation of fatty acids, the crispiness of bread’s crust or of sugar entering a solution. The other advantage is that neutrons are sensitive for structures that range from nanometres (read: molecules) up to tens of micrometers – the size of microstructures in food. “Unlike a microscope, a neutron beam will measure the average properties of a macroscopic quantity of food,” explains Bouwman.

In order to measure such properties, the neutrons, originating from the nuclear reactor’s active core, need some sophisticated manipulation. That’s what happens in the 5-meter long ‘Sesans’ set-up. First, the neutrons are polarised: only neutrons with a specific direction of spin can pass. A set of two electromagnets then separates the neutrons based on their spin state (up or down). Incidentally, quantum mechanics allows neutrons to possess both spin states at the same time. The separated neutron spin states then pass through a food sample, after which another set of electromagnets reunites the spin states just before they hit the neutron detector. Sesans stands for Spin-Echo Small-Angle Neutron Scattering.
In absence of a sample, the bundle will be just as polarised as in the beginning and nothing much can be seen. If however one of the neutron spin states is more delayed by the passage through (for example) fat globules than the others, a loss in polarisation will occur. This polarisation, measured by the neutron detector, reflects the sample’s inner structures. By varying the strength of the magnetic fields, it may be tuned from nanometres up to 20 micrometres. No images spring from these measurements - just graphs whose peaks and troughs provide researchers with intriguing clues of the underlying biochemical processes.

Take yoghurt making, for instance. Traditionally, it’s known that one needs to add lactic acid producing bacteria to milk in order to make milk proteins clot. Food technologist Sofie Ossowski, from the University of Lund (Sweden), has ‘neutronised’ various steps in the yoghurt-making process. She established that at first 0.3 micrometer aggregates form, which after acidification grow into 10-micrometre lumps. She also discovered that whey helps stabilise the larger aggregates, which translates into a better preservation of the product.
“You can watch the process occurring,” says Bouwman. “In yoghurt you can see 0.1 micrometer protein clots lumping into 5 micrometer chunks.” Such protein or fat lumps typically occur in dairy products, sauces, mayonnaise and peanut butter. The coagulate size seems indicative of the freshness, which is another line of research: Which treatments result in longer shelf lives and increased freshness.
As for the upcoming workshop, Bouwman hopes to convince food research and industry representatives of neutrons’ potential for improving the understanding of the biochemical processes in food production. Now who would have thought that neutrons could actually be good for you? 

http:// www.neutronfood.nl

What makes bread crispy? Nuke to find out. (Photo: Wikimedia)