Acidified milk drinks have become increasingly popular in recent years due to their health benefits and unique flavor. However, these drinks can be challenging to stabilize, as the acid in the milk can cause the proteins to denature and form aggregates, leading to sedimentation and separation. One effective method of stabilizing acidified milk drinks is through the use of carboxymethyl cellulose (CMC), a water-soluble polymer that can interact with proteins and other ingredients to form stable suspensions. In this article, we will discuss the action mechanism of stabilization of acidified milk drinks by CMC.

Structure and Properties of CMC

CMC is a derivative of cellulose, a natural polymer found in plant cell walls. It is made by chemically modifying cellulose with carboxymethyl groups, which improve its water solubility and other properties. CMC is a highly branched polymer with a long linear chain backbone and many side chains of carboxymethyl groups. The degree of substitution (DS) of CMC refers to the number of carboxymethyl groups per cellulose unit, and it determines the degree of solubility and viscosity of CMC.

Action Mechanism of CMC in Stabilizing Acidified Milk Drinks

The addition of CMC to acidified milk drinks can improve their stability by several mechanisms:

1. Electrostatic Repulsion: The carboxymethyl groups on CMC are negatively charged and can interact with positively charged proteins and other ingredients in the milk, creating a repulsive force that prevents the proteins from aggregating and settling. This electrostatic repulsion stabilizes the suspension and prevents sedimentation.
2. Hydrophilic Interactions: The hydrophilic nature of CMC allows it to interact with water molecules and other hydrophilic components in the milk, forming a protective layer around the proteins and preventing them from interacting with each other.
3. Steric Hindrance: The branched structure of CMC can create a steric hindrance effect, preventing the proteins from coming into close contact and forming aggregates. The long, flexible chains of CMC can also wrap around the protein particles, creating a barrier that prevents them from coming into contact with each other.
4. Viscosity: The addition of CMC to acidified milk drinks can increase their viscosity, which can prevent sedimentation by reducing the settling velocity of the particles. The increased viscosity can also create a more stable suspension by enhancing the interactions between the CMC and other ingredients in the milk.

Factors Affecting the Stabilization of Acidified Milk Drinks by CMC

The effectiveness of CMC in stabilizing acidified milk drinks depends on several factors, including:

1. pH: The stability of acidified milk drinks is strongly influenced by the pH. At low pH values, the proteins in the milk become denatured and form aggregates more easily, making stabilization more challenging. CMC can stabilize acidified milk drinks at pH values as low as 3.5, but its effectiveness decreases at lower pH values.
2. Concentration of CMC: The concentration of CMC in the milk affects its stabilizing properties. Higher concentrations of CMC can lead to increased viscosity and improved stabilization, but too high concentrations can result in undesirable texture and flavor.
3. Protein Concentration: The concentration and type of proteins in the milk can affect the stability of the drink. CMC is most effective at stabilizing drinks with low protein concentrations, but it can also stabilize drinks with higher protein concentrations if the protein particles are small and evenly distributed.
4. Processing Conditions: The processing conditions used to produce the acidified milk drink can affect its stability. High shear forces and heat can cause protein denaturation and aggregation, leading to instability. Processing conditions should be optimized to minimize protein.