by Dr. Wesley De Boever, Product Marketing Manager, TESCAN
Dynamic micro-CT acquires data continuously, enabling scientists to capture data from unpredictable events that may be missed with conventional time-lapse techniques. Dynamic micro-CT is particularly valuable for food sciences because it allows researchers to visualize the 3D change in internal structure while undergoing physical change such as baking or melting. Watch this short video to see in real-time the baking process of biscuits and cookies, sugar melting and an Oreo cookie breaking test:
Case Study: Analysis of Beer Head
Beer head is the frothy foam on top of beer. The head is produced by bubbles of gas, predominantly carbon dioxide, rising to the surface. The elements that produce the head are wort protein, yeast and hop residue. One could certainly argue that the foam plays an important role in the high quality of beer, but why?
Figure 1: 3D renderings of three different time points (0, 2, and 9 minutes) of the beers used for this comparison. Clear differences are seen in the consistency of the foam head between the two types of beer. The lager foam has all but disappeared by 9 minutes, while the strong ale is holding up well.
We examined the collapse of a beer foam and compared the differences between two types of beer using dynamic micro-CT. In one case the foam stays intact over a long period of time while the foam dissipates quite quickly in the second case. Why is this important? Smell is an integral part of taste, and the beer head acts as a carrier for the aromatics of a beer. The fact that a beer that goes “flat” tastes different isn’t just due to less “fizziness,” but it’s also because the aromatics are less available, therefore changing the taste of the beer.
In this experiment1 two different beer types are imaged in the TESCAN DynaTOM, a unique gantry-based system where the sample remains stationary while the X-ray source and detector rotate. This allows for a maximum amount of flexibility when working with complex in situ samples or, as is the case with beer foam, delicate samples that may be distorted by the simple action of rotating the sample in a traditional micro-CT system.
For beer 1, a Belgian strong ale, 70 rotations about the sample with 15 seconds per full 360-degree rotation at 160 µm voxel size were collected, resulting in a total experiment time of 17.5 minutes. For beer 2, a lager, the conditions were slightly different with 80 rotations about the sample, 9.4 seconds per full 360-degree rotation, and 150 µm voxel size, resulting in a total experiment time of 12.5 minutes. The foam from each sample was then analyzed to show the relation of the average equivalent diameter (AED) of the pores and the height of the foam, resulting in some stark differences between the two beverages.
In the Belgian ale, a much smaller equivalent pore diameter, resulting in a much more resilient and dense foam, was observed in comparison with the lager. A main takeaway of this experiment: make sure to drink a lager beer quickly, but take some time when enjoying an expressive and flavorful Belgian strong ale! In all seriousness, this type of imaging and analysis can be transferred to several other lightweight foam applications, including the evolution of polymeric foams during production or under corrosive environments.
Figure 1 provides a comparison of 3D renderings of the foam of the two different beers at several time points, while Figure 2 demonstrates segmented results of the foam pores at different time points for the Belgian strong ale.
TESCAN is a pioneer in lab-based dynamic CT with systems engineered to provide the flexibility of traditional micro-CT for routine imaging needs, while also providing several essential characteristics for enabling dynamic CT.
Figure 2: Segmentation and analysis of the foam pore sizes were performed across all 80 data sets. Shown are examples at four different time points, where the color represents the size of the pore (blue, smallest; red, largest).
Along with optimizing standard parts of the system (X-ray source, sample rotation and detector) for high temporal resolution, a number of other key elements are in place for dynamic CT.
Specifically, “no cable wrap” continuous rotation for in situ apparatuses, in situ interfaces for simple swapping of test rigs, and unique temporal reconstruction and analysis techniques that allow users to leverage the full benefit of continuous data. The hardware and software tools allow individual scans down to a few seconds and temporal discretization near the rate of individual radiographs, which may be on the order of 20 ms or better.
Watch the case study video:
References:
- J Dewanckele et al., J Microsc (2020) doi:10.1111/jmi.12879.
About the Author: Wesley De Boever is Product Marketing Manager for Dynamic Micro-CT at TESCAN. He holds a Ph.D. in Geology, obtained as a researcher at the Ghent University Centre for X-Ray Tomography (UGCT). Wesley has over a decade of experience in conventional and dynamic micro-CT and its combination with other microscopy techniques such as optical and scanning electron microscopy.