Effects of processing on rheology and structure of double cream cheese

Double cream cheese curd was industrially made and post-treated in a pilot scale plant. After storage at 5 degrees C for 7-9 days, rheological properties of the intermediate and final products were measured using penetrometry, flow curves recording and dynamic testing. Results showed that the curds exhibited time-dependent hysteresis of the flow properties and polymer-like dynamic viscoelastic behaviour, independently of the manufacturing stage. Curd mixing at 70 degrees C and 500 r.p.m. with salt and predenatured whey protein concentrate and dynamic cooling at 20 or 13 degrees C decreased firmness and dynamic viscoelastic parameters G' and G '', while tan delta (G ''/G') increased. There was a breakdown of the curd with a decrease in elastic deformation, typical of a solid material and a corresponding increase in viscous flow, characteristic of a liquid. On the other hand, evolution of the rheological parameters was the reverse after heat treatment at 85 degrees C and homogenization at 20 MPa (first stage) + 5 MPa (second stage). The curd structure was developed with a transition of behaviour to that typical of an elastic solid. Curd cooled dynamically to 13 degrees C became unstable during subsequent storage. This phenomenon was thought to result from an important breakdown of the curd during dynamic cooling and from aggregation of the milk fat globules during storage. (C) 1996 Canadian Institute of Food Science and Technology. Published by Elsevier Science Ltd.