The effect of rennet casein hydration on gel strength and matrix stability of block-type processed cheese

Abstract

• Calcium removal and casein network formation with different ES time dependant. • Increased pH reduces hydrophobic and increases electrostatic casein interactions. • Increased hardness and meltability in cheeses with casein at maximum hydration. • Electrostatic interactions in product less affected by changes in hydration time. In this study, the effect of rennet casein hydration on the properties of a block-type processed cheese was explored by varying casein hydration in the presence of water and different emulsifying salts between 0−120 min. Both hydration time and emulsifying salt type were observed to have distinct effects on casein hydration, with gel strength increasing with increasing hydration time to a point of maximum viscosity dependant on the specific salt used. The rate of hydration was found to be directly proportional to calcium sequestration rate of the emulsifying salt. Use of rennet casein gel at maximum gel strength in the manufacture of a block-type processed cheese lead to an increase in cheese hardness, meltability and fat homogenisation due to the increase in protein intermolecular bonding as identified by changes in ester and alcohol IR frequencies. This work is of significance to the dairy industry as it shows accurate determination of optimal casein hydration conditions can directly affect casein functionality and product characteristics.