Research On The Gelling Mechanisms Of Casein And Carrageenan

This experiment mainly regard casein-carrageenan complex system as the research object, the effect of different factors on the gel properties and rheological properties of the system was studied.The main form of interaction between casein and carrageenan was discussed.Through thermal dynamic analysis and detection the changes of protein functional groups before and after the reaction which reveals mechanism of casein and carrageenan gel, and the microstructure of the gel was observed.Under the low pH level,the gel strength of casein-carrageenan increased with the pH, pH=4, gel strength reached the maximum value of 785.321g,and then show a downward trend. The ratio of casein and carrageenan is l,gel strength of 749.738g,at this time the gel texture is better. Weakening effect on gel strength of NaCl is strong,at the concentration of 1.0mol/L,the gel strength from 356.656g down to 28.658g,loss rate as high as 91.96%. Casein-carrageenan system compared with casein alone,melting endothermic peak broadening and the phase transition temperature from 88.6℃ increase to 90.1℃.The system exhibits pseudoplastic fluid characteristics.With the increasing amount of carrageenan,flow index n dropped from 0.9251 to 0.7270,consistency coefficient K rised from 0.3796 to 3.4403,and with different concentration of carrageenan,the system elastic modulus G’is greater than the viscous modulus G",with carrageenan added the system varies with frequency stability improved. The interaction between carrageenan and casein were mainly attributed to electrostatic interaction,the power of the hydrogen bonding and covalent disulfide bonding are followed, hydrophobic function is the weakest.The increased consentration of carrageenan would result in increased particle size of the system/when the concentration was 0.5%,the molecule size could reach to 1096.8nm,almost five times of the molecular diameter of casein.Infrared spectroscopy analysis showed that casein-carrageenan system at 2924cm-1 and 1746cm-1 appeared two new peaks. At 3307cm-1 N-H bond stretching vibration absorption peak shift to higher wave number at 3430cm-1,secondary structure of protein changed. In four kinds of monomer casein,asi-casein is the main component of gel apart.Casein-carrageenan system’s network structure with the increase of carrageenan percentage become more compactness. Calcium ion play an important role in the gel formation process of casein and carrageenan.Add carrageenan in decalcified milk can not happen gel reaction and the composition of protein is unchanged.