Evaluation of cattle skin collagen for producing co-extrusion sausage casing

Co-extrusion is a fully automated sausage production process that employs a continuous stream of collagen dispersion to encase the extruded meat mass to form an endless sausage rope, that is later crimped into links of selected sizes. Fibrous and soluble type I collagen dispersions obtained from bovine skins of animals aged 18–36 months is used as the raw material for these dispersions. In this study, the chemical and physical properties of cattle skin collagen preparations from four sources [American Calf (AC), Dutch Heavy Veal (DHV), Danish Ox and/or Heifer (DOH), and Heavy German Cow (HGC)] were investigated for their potential application as collagen source for co-extrusion. All dispersions exhibited shear-thinning behavior, following a power-law model with k* values for HGC, DHV, AC, and DOH dispersions of 59, 68, 95 and 114 Pa sn*, respectively. Rheological measurements showed for all dispersions a decrease in elasticity and loss modulus at 35–40 °C. SDS-PAGE indicated the presence of α1(I)- and α2(I)-chains of type I collagen for all dispersions. The mechanical strength of the films was 1.6, 1.6, 1.3 and 1.2 MPa for films prepared from AC, DOH, DHV and HGC dispersions, respectively. After crosslinking a 27% reduction of free amine groups was found for HGC and DOH, followed by 26 and 19% for AC and DHV, respectively. Based on the properties of the dispersions and the films in relation to the co-extrusion process AC, DHV and DOH are potentially suitable as an alternative collagen source.