THE HYDRATION BEHAVIOR OF RENNET CASEINS IN CALCIUM CHELATING SALT SOLUTION AS DETERMINED USING A RHEOLOGICAL APPROACH

Rennet casein is used in the manufacture of Mozzarella cheese analogue s. Hot solutions of calcium chelating salts are used to facilitate hyd ration of the protein which subsequently acts as an emulsifier for the oil phase dispersed in the protein/aqueous phase of the cheese analog ue. On cooling, a matrix resembling cheese in texture and other rheolo gical properties is produced. Considerable variations in the functiona l performance of different rennet caseins during cheese analogue manuf acture have been observed. Commercial rennet caseins have been obtaine d and are being studied to establish the nature and causes of these va riations in performance. A simplified model system to study rennet cas ein hydration was developed. The method involves dispersing rennet cas eins in solutions of chelating salt at 55 degrees C with stirring. The changes in viscosity index that occur as the rennet casein hydrated w ere followed using a controlled shear rate rheometer equipped with a c ustom designed paddle stirrer. Hydration of the rennet casein particle s was found to occur in a number of stages including particle swelling , clumping, network formation and subsequent breakdown of the network. Considerable variations in the times taken for different rennet casei ns to swell, clump and reach maximum viscosity index and in the stabil ity of the hydrated protein dispersions were found. The rheological pr operties of the rennet caseins during hydration were highly dependent on the concentration of the chelating salt in the hydrating solution. (C) 1998 Elsevier Science Ltd. All rights reserved.