Fusion of skim milk cheese curd grains: Development of a method to measure the fracture stress of the bonds between fused curd grains

An experimental technique with which to measure the fracture stress of fused curd grains, submerged in ultrafiltered milk permeate, has been developed and applied to curd grains of rennet-induced skim milk at pH 6.40 during the first 25 min of fusion. Effects of applied compressive stress within the range of 25-50 Pa, syneresis time, fusion time and tension loading rate were investigated. Fracture stress increased with applied compressive stress and fusion time. For the system investigated it was found that very small changes in applied compressive stress dramatically increased the degree of fusion. The degree of syneresis prior to fusion was found to have a large impact on the fusion rate, The rate of fusion was greater for 30 min of syneresis compared to 6 min of syneresis. A longer syneresis time, up to 60 min, did not further improve the fusion rate.