(a) Processing operations. The manufacturer shall employ appropriate quality control procedures to ensure that finished foods do not present a health hazard.

1. (1) Acidified foods shall be so manufactured, processed, and packaged that a finished equilibrium pH value of 4.6 or lower is achieved within the time designated in the scheduled process and maintained in all finished foods. Manufacturing shall be in accordance with the scheduled process. Acidified foods shall be thermally processed to an extent that is sufficient to destroy the vegetative cells of microorganisms of public health significance and those of nonhealth significance capable of reproducing in the food under the conditions in which the food is stored, distributed, retailed and held by the user. Permitted preservatives may be used to inhibit reproduction of microorganisms of nonhealth significance (in lieu of thermal processing).
2. (2) Sufficient control, including frequent testing and recording of results, shall be exercised so that the finished equilibrium pH values for acidified foods are not higher than 4.6. Measurement of acidity of foods in-process may be made by potentiometric methods, titratable acidity, or colorimetric methods. If the finished equilibrium pH of the food is above 4.0, the measurement of the finished equilibrium pH shall be by a potentiometric method, and the in-process measurements by titration or colorimetry shall be related to the finished equilibrium pH. If the finished equilibrium pH is 4.0 or below, then the measurement of acidity of the final product may be made by any suitable method. Special care should be taken when food ingredients have been subjected to lye, lime, or similar high pH materials.

3. (3) Procedures for acidification to attain acceptable equilibrium pH levels in the final food include, but are not limited to, the following:

   1. (i) Blanching of the food ingredients in acidified aqueous solutions.
   2. (ii) Immersion of the blanched food in acid solutions. Although immersion of food in an acid solution is a satisfactory method for acidification, care must be taken to ensure that the acid concentration is properly maintained.
   3. (iii) Direct batch acidification, which can be achieved by adding a known amount of an acid solution to a specified amount of food during acidification.
   4. (iv) Direct addition of a predetermined amount of acid to individual containers during production. Liquid acids are generally more effective than solid or pelleted acids. Care must be taken to ensure that the proper amount of acid is added to each container.
   5. (v) Addition of acid foods to low-acid foods in controlled proportions to conform to specific formulations.
4. (4) Testing and examinations of containers shall occur often enough to ensure that the container suitably protects the food from leakage or contamination.