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    Micro-CT of Miniature Fruitcake

    Using the Bruker SkyScan 1173

    Product Inspection: Using micro-CT to study consumer food products

    Now that the year is coming to a close and we all slow to spend time with friends and family, many will gather to share gifts. No other gift is both so ingrained in the holiday season, as well as infamous, than the common fruitcake. While today a fruitcake is thought of by many as a dense, chewy reminder of past generations, for some the fruitcake will always hold a special place in their hearts. Yet, for all the jokes aiming at the reputation of this humble cake, its presence on store shelves continues to this day1.

    Micro-CT is a powerful tool for the inspection of consumer food products as it offers a way to non-destructively image samples2,3. This unique process results in a three dimensional reconstruction allowing for inspection of the internal structure of the product and segmentation of different phases with sufficient electron density differences. Using the reconstructed data, one can help ensure product quality or explore the effects of ingredient and process changes on the final product quantitatively. One measure to compare these changes for baked goods, such as fruitcakes, would be to study the change’s effect on porosity.

    Figure 1: Cross sectional views of a fruitcake

     

    Micro-CT Scan of a miniature Fruitcake

    After reconstructing the X-ray attenuation data into representations of the three-dimensional structure we can observe the different phases present within the internal structure of this fruitcake from different planar views (Figure 1). In this case, we focused in on a dense inclusion, presumably a dried fruit piece, within the cake’s center. However, we can also observe the large air pockets within the bread structure, especially near the top of the cake.

    Table 1: Calculated Porosity Values

    Sample Miniature Fruitcake
    Total Volume (mm3) 269142
    Open Porosity (%) 53.1
    Closed Porosity (%) 1.16
    Total Porosity (%) 53.7
    Avg. Pore Diameter (mm) 1.91

     

    Figure 2: Pore diameter distribution plotted against pore contribution to total pore volume

    These air pockets can be further analyzed to determine the effective open and closed porosity of the cake along with a distribution of pore sizes (Table 1). After calculating the volume properties of the scan data, we can generate a pore distribution (Figure 2) and a model of pore sizes throughout the cake (Figure 3). Using this information, scans from the same product with changes made to either ingredients or processing conditions can be directly compared quantitatively to study identify the key factors influenced by the change or to help with product development.

    Figure 3: Cross-sectional view of modeled pores colored by diameter

    Figure 4: Reconstructed top-down cross-section view of fruitcake

    Due to the difference in X-ray attenuation between the dense dried fruit particles and the spongey cake, the two phases can both be readily separated from one another, along with the air contained in the pockets (Figure 4). In this rendered three-dimensional view, the higher density fruit inclusions are colored in red, the cake is brown, and the air is represented by black.

    Figure 5: Fruitcake examined in this study

    For this study, we examined the porosity of a common, off-the-shelf Italian fruitcake containing raisins along with candied orange, papaya, and citron4. While we are able to separate the fruits from the cake, we are unable to distinguish one type of candied fruit from another because of their similar X-ray attenuation values since each likely has a similar density and water content.

    Conclusion

    Micro-CT excels as a tool to nondestructively examine the internal structure of food products and continues to be successfully applied in the inspection of assembled products. We hope you found this Image of the Month interesting. If you have an Image of the Month sample that you would like us to scan, please contact us by calling Seth Hogg at 610-366-7103 or e-mailing seth.hogg@microphotonics.com

    Scan Specifications

    Sample Miniature Fruitcake
    Voltage (kV) 80
    Current (µA) 92
    Pixel Size (µm) 50
    Rotation Step 0.3
    Scan Time (HH:MM:SS) 01:49:38

     

    All scans completed on our high-speed SkyScan 1173 micro-CT system at the Micro Photonics Imaging Laboratory in Allentown, PA. Reconstructions were completed using NRecon and visualization of 2D and 3D results were completed using DataViewer and CTVox.

    Works Cited

    1. https://www.smithsonianmag.com/arts-culture/fruitcake-101-a-concise-cultural-history-of-this-loved-and-loathed-loaf-26428035
    2. http://www.sciencedirect.com/science/article/pii/S002364381730590X
    3. https://iufost.edpsciences.org/articles/iufost/pdf/2006/01/iufost06000023.pdf
    4. https://en.wikipedia.org/wiki/Panettone

     

     

     

     

     

     

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