CMC sodium carboxymethyl cellulose is a water-soluble cellulose ether obtained by chemical modification of natural cellulose. Due to the poor water solubility of carboxymethyl cellulose acid structure, in order to be able to apply it better, its products are generally made into sodium salt. CMC sodium carboxymethyl cellulose is a white to light yellow powder, granular or fibrous substance. It has strong hygroscopicity and is easily soluble in water. When it is neutral or alkaline, the solution is a high-viscosity liquid. Stable to drugs, light and heat. But the heat is limited to 80 ℃, if it is heated above 80 ℃ for a long time, the viscosity will decrease and it will not dissolve in water. It is brown when heated to 190-205°C, and charred at 235-248°C. Its solubility in water depends on the degree of substitution. It is insoluble in acid and alcohol, and does not precipitate when exposed to salt. It is not easy to ferment, has great emulsifying power to oil and wax, and can be stored for a long time.
There are two main reasons for adding hydrocolloids in dairy products. On the one hand, the hydrocolloid can improve the texture of the product. On the other hand, it can extend the shelf life of dairy products, prevent whey precipitation, protein aggregation and milk fat separation, and has a certain emulsification effect. In the past, the functionality of hydrocolloids in milk systems was only attributed to the thickening, gelling and emulsification of the hydrocolloids themselves in the solution, but this explanation is not very reasonable. Studies have shown that the interaction between hydrocolloid and casein in acidified milk is the dominant factor.
Studies have shown that when the concentration of sodium carboxymethyl cellulose in food is less than 0.2%, the added CMC sodium carboxymethyl cellulose can be completely absorbed by casein. The supernatant of high-speed centrifugation does not contain CMC sodium carboxymethyl cellulose. The milk system is in an unstable state. As the concentration of CMC sodium carboxymethyl cellulose in the food increases, unadsorbed CMC sodium carboxymethyl cellulose can be detected in the supernatant. At this time, the CMC sodium carboxymethyl cellulose can produce saturated adsorption on the surface of casein. However, there is no weak gel network structure in the system at this time, and the CMC sodium carboxymethyl cellulose in the unadsorbed food only plays a role in increasing the rigidity of the system. The increase in stiffness can slow down the sedimentation rate of casein particles and promote the improvement of the stability of the acidified milk system.
In addition, it was found that although the sodium carboxymethyl cellulose in the adsorbed food does not desorb over time, it may be degraded like the sodium carboxymethyl cellulose in the unadsorbed food under acidic conditions. It is also one of the main reasons that cause precipitation and instability of acidified milk beverages during storage. Over time, it can lead to shortening of shelf time.