Cryogenic Imaging of Extrudate Morphology

The morphology of the extrudates was analysed by cryo-imaging [10 (link)]. For this purpose, the frozen samples were cut laterally to the flow direction (side view) with a cryo-microtome (CM 3050, Leica Biosystems GmbH, Nussloch, Germany). A cooling room temperature of −14 °C and a sample holder temperature of −12 °C were set for the instrument. To prepare the extrudates for cutting, 4–5 cm long sections were cut out from the extrudate strand. These sections were attached to the sample holder with a sectioning medium from Leica Biosystems GmbH (FSC 22 Frozen Section Media, Nussloch, Germany). This ensured product stability on the sample holder during sectioning and had no influence on the product microstructure. By cutting 40-µm sections from the extrudate, smooth cut surfaces were obtained. Photos of the cut surface were taken immediately after cutting of the extrudate in the cryo-microtome with a digital camera (DMC-GH2, Lumix, Kadoma, Japan) and a 4608 × 3456 pixel resolution.