In building up a control system, it is important to consider in each step of cheese production, from the farm to the final product, the microorganisms of concern. These steps are called critical control points, and by introducing hazard analysis of critical control points (HACCP), it is possible to introduce a very high safety level in the products. Critical control points are production steps in which some of the physiological or chemical conditions could cause a change conducive for growth of unwanted microorganisms. This means that careful evaluation should be performed if the microorganisms of concern can survive or grow at each control point. The most important parameters to evaluate are temperature; process time at the given temperature; pH and possibility of change in pH; water activity; and addition or formation of inhibitors.
There are different tools for determining whether a control point is critical. One is Predictive Modeling. Predictive Modeling is based on entering a large dataset on the growth of different microorganisms under different conditions into a database system. The growth data on the microorganisms derived from laboratory research, challenge tests, and real product experiences are analyzed statistically and a program is formed that predicts the microorganisms growth at selected temperatures, water activities, pH values, and often under other conditions such as the presence of additives.
Another critical point is the cleaning system. In most dairies, cleaning in place (CIP) is used. Sodium hydroxide with a pH of about 11 and a temperature of 70-80°C is used to wash away most of the milk components from the equipment, followed by flushing with water. Nitric acid at about pH 2 is then used to remove acid-soluble components from the equipment. It is expected that the strength of the CIP and the temperature will drop during the long transportation distances. In both cases, the cleaning efficiency and the direct killing effect on microorganisms will be less. Thus, CIP is an important critical control point. Once the critical control points are established, limits for accepted values are determined and controlled with selected intervals.
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