Preparation of the Processed Cheese Possessing Fibrous Structure by Extrusion Cooking

Abstract

Manufacturing conditions for the processed cheeses possessing fibrous structure using a twin screw extruder and a conventional kettle-type cooker were investigated. Two types of cheeses, Gouda cheese ripened for 2 weeks and Emmental cheese ripened for 8 months, were used, and whey protein concentrate (WPC, protein conc. 75%) was added to each cheese at optimum concentration to obtain fibrous structure. In extrusion cooking, each ground cheese blended with WPC was fed into a barrel and cooked at 70-90°C. The extruded thermoplastic mass was cooled to approx. 45°C in a low-shear kneader and stretched to obtain fibrous structure. In both cheese types, fibrousness of the resultant products cooked at 70 and 80°C was satisfactory and superior to that at 90°C. Observation of the products under an optical microscope indicated that cooking temperature was correlated with fibrousness. A decrease of fibrousness, occurred when cheese was cooked at 90°C, was due to mutual adhesion of protein strand by heat. When kettle-type cooker was employed, fibrousness of the product cooked at 80°C for 0 min was inferior to that cooked at the same temperature by the extruder, and an increase of holding time at 80°C during cooking was also found to affect fibrousness adversely. A twin screw extruder which can complete cooking in short residence time was indicated to be suitable for manufacturing processed cheese possessing fibrous structure.