Background: In today's sausage production, various types of casings are employed including: natural, manufactured collagen, cellulose and plastic, as well as the new type of co-extruded casings made of collagen, alginate or alginate-collagen hybrids. Casings play important functional roles in sausage production from stuffing right up until the consumer eats the product. The selection of the right casing is critical as it influences the integrity, size and shape of the sausage while converting the soft, flowable raw meat batter into the desired semi-rigid sausage. The two most important casings' physical properties are their barrier properties and mechanical strength; both strongly affect consumer's perception of bite/snap and flavor. Scope and approach: Currently edible casings include natural sheep and pig intestines as well as collagen originating from bovine skins. This review focuses on the various aspects of latter collagen used for co-extrusion production, of high quality sausages in an economical way. Key finding and conclusions: Currently these relatively new co-extrusion gels come only with basic information about pH, protein content, and microbial counts, but nothing about physical characteristics such as viscosity, work to extrude and shear thinning properties. This is important as variations in collagen structure and functionality can be the results of environmental factors such as nutrition, housing, as well as age and genetics. Overall, the rising costs and shortage of intestines and increasing need for Kosher and Halal products, is putting pressure on collagen manufacturers to look for alternative sources with best performance, as described in the review.