North Carolina A & T State University
During enzymatic coagulation of milk, three separate but overlapping processes occur: (1) enzymatic hydrolysis, (2) aggregation, and (3) gelation. These processes must occur successfully in order to produce a desirable milk coagulum for cheese production. Key to the success of these processes is having the appropriate levels of calcium concentration, pH value, and active enzymes (rennin). If any of these are not at optimum levels, then the degree of milk coagulation will be negatively affected. What can cause suboptimal levels of these factors is the presence of foreign matter or chemical substances. For example, if a substance that acts as chelating agent is introduced, it could bind with calcium and make it unavailable for the coagulation process. Similarly, the addition of agents that increase the pH value could slow or inhibit the coagulation process. Additionally, if a toxin was introduced it might act as an enzyme inhibitor, resulting in failure of the coagulation processes to reach successful completion. Because of these potential vulnerabilities it is important to study the impact that selected substances might have on the coagulation properties of milk proteins. It is critical that we develop a better understanding about how foreign substances that may be introduced into milk might affect its quality and suitability for processing into other foods (i.e., cheese). Because introduced foreign substances or agents can alter the coagulation process or affect the forming of coagulum, we propose to characterize the effects of selected substances/agents to determine if properties of the coagulation process can be used to identify the presence of these contaminants. In this study coagulation properties will be determined by measuring milk viscosity during the initial stage of milk coagulation. In addition, we plan to study the impact select rodenticideson the coagulation properties of milk proteins. Coagulation indicators to be evaluated include the degree of casein hydrolysis during the initial stage of milk coagulation, zeta potential measurements, gel formation, and rheological properties of milk coagulum. Due to multifunctional production process involving converting milk to cheese, there is a great potential for intentional contamination in any processing stage. It is estimated that toxins concentrations are 3-4 folds higher in cheese curd than in milk. If such products reached consumers, it could create a public health crisis. Therefore, it is important to understand the interaction between chemically adulterating agents and milk proteins during cheese processing to help identify intentional contamination of milk that would likely lead to better isolation of the contaminating substance. This can be critical in reducing time lost to processing an unusable food product as well as reducing the need for unnecessary destruction of usable milk and milk products. Results obtained from this research would be important for interventions and countermeasures in preventing final retail distribution and consumer consumption of intentionally contained food.