No functionality without a pleasant taste – consumers will only buy products that meet their sensory quality criteria regarding both taste and texture. Due to resource-intensive meat production, high-quality meat analogues as a sustainable alternative represent a major challenge for science and industry. Extrusion cooking is a promising technology to generate textured vegetable proteins. Bio-polymers such as starch and proteins are plasticized with water and subjected to mechanical and thermal energy treatment to achieve a desired texture that resembles meat1. The textural properties of extruded vegetable-protein products are a decisive factor for consumer acceptance and are closely related to their microstructure. In addition to texture measurements, imaging methods can be used to describe the microstructure of food. Most conventional measurements focus on destructively prepared slices or the surfaces of food. X-ray microtomography enables a nondestructive three-dimensional microscale insight into samples2. Our aim is to identify structural key parameters for mimicking the structure of meat. Therefore, meat samples are compared to different extruded vegetable-protein products by means of X-ray microtomography. Pea-protein products have been texturized both at low-moisture (< 35%) and high-moisture conditions (> 50%) using a laboratory co-rotating twin-screw extruder with a length:diameter ratio of 25:1 and a mass flow of 1 kg/h. Freeze-dried samples have also been prepared with the aim of achieving a better contrast resolution. The three-dimensional images were taken by a custom-built X-ray microtomography system, which is optimized for biological specimens. Image analysis was performed with the commercial software MAVI. The difference in structure between meat and meat analogues is visually observable. Meat shows orientated muscle fibers consisting of different types of tissue. Extrusion samples exhibit homogeneous, continuous fibers with a less strict orientation. Structural parameters that are sensitive to the size, shape, and orientation of fibers and pores describe these differences.
1. R. Guy (Editor), 2001, Extrusion cooking, Woodhead Publishing.
2. P. Frisullo, R. Marino, J. Laverse, M. Albenzio & M.A. Del Nobile, 2010, Meat Science, 85 (2), 250-255.
Prof. Dr. Ing. Heiko Briesen heiko.briesen@mytum.de
Dr. Ing. Peter Eisner peter.eisner@ivv.fraunhofer.de
