Effect of heat treatment on the physical properties of milk gels made withboth rennet and acid

The effects of heat treatment of milk, and a range of rennet and glucono-de lta -lactone (GDL) concentrations on the physical properties of combined re nnet/acid gels, made from reconstituted skim milk at 30 degreesC, were inve stigated. Microstructure was determined using confocal scanning laser micro scopy and permeability measurement. Whey separation was determined using tw o differently shaped containers. Confocal scanning laser micrographs of com bined gels made from unheated milk showed that these gels had much larger p ores compared with combined gels made from heated milk. This trend was conf irmed by permeability measurements. Combination gels made from unheated mil k were very prone to spontaneous whey separation, possibly due to considera ble rearrangements of aggregated particles at an early stage of the gelatio n process. Gels made with both rennet and acid are a useful model system fo r studying the behaviour of natural and fresh cheese products. (C) 2001 Els evier Science Ltd. All rights reserved.