Why is it that the crispy crust on a spring roll can become so soggy after it has been frozen? The presenter of the Dutch regional television programme Trots op Gelderland (‘Proud of the Province of Gelderland’) took this question to Wageningen UR, where she was given a ‘spring roll analysis’ demonstration on the XRT, or X-ray computer tomography (XRT/CT) as the technology is officially known. The scanner is operated by CAT-AgroFood, which is responsible for the shared research facilities at Wageningen UR.
Marjolein van der Glas, Business Development Manager for Fresh Food and Chains at Wageningen UR Food & Biobased Research, explains in the programme how XRT was used to analyse the composition of the outer layer for a spring roll manufacturer. Operator Remco Hamoen shows how the XRT scans the spring roll as it rotates. He explains that the system makes a series of X-rays, which the XRT software merges to produce a clear 3D picture of the spring roll. This makes it possible to see not just the outside, but also a cross section wherever required, without having to actually cut into the spring roll.
The colours on the virtual cross section of the spring roll show a clear distinction between the vegetables and meat on the inside and the pockets of air between the pastry layers on the outside. The analysis shows that spring rolls with a soggy crust have far fewer air pockets between the layers. Marjolein van der Glas explains that Wageningen UR and the manufacturer are now investigating how to maintain the structure with lots of layers of air in the crust of the spring roll, also after freezing.
The XRT can be used not just for research into food products, but a wide range of other samples too. For example, it can be used to analyse the porosity of soil samples, the root structure of plants, or the exact dimensions of objects. The XRT facility at Wageningen UR is available for use by interested researchers from all organisations.
Watch the Trots op Gelderland TV programme from 11 March 2015 here. The XRT item starts after 14 minutes and 11 seconds (at 14.11).