Sanitizing Milking Equipment
Cleaning reduces bacterial numbers on surfaces but does not eliminate all types of bacteria. The sanitizing of surfaces within 30 minutes of the next milking destroys nearly all lingering organisms if: (1) the sanitizing solution used is of proper strength, and (2) a thorough cleaning precedes the sanitizing. Improper cleaning results in residual soils that can protect bacteria from the sanitizing action. Some sanitizing compounds lose strength with time in storage (chlorine compounds) or increasing pH (chlorine and iodine compounds). Some are unstable at temperatures above 120°F (iodine compounds), while others are not compatible with hard water (quaternary ammonium compounds).
Cleaning Procedures
Equipment and bulk tank cleaning procedures should be posted on the milk-house wall and rigidly followed. An example of equipment cleaning procedures is presented in Table 1. The precise course of action, compounds used, and water temperatures will vary. In general, equipment should be rinsed with lukewarm 100 to 110°F water immediately after milking to prevent drying of milk solids on surfaces. Water that is too hot can cause denaturation of proteins and a protein film on surfaces, while water that is too cold can cause fat crystallization and the formation of a greasy film on surfaces.
Washing and rinsing should follow. Wash water should remain above 120°F. Start with water at 170°F. In clean-in-place (CIP) systems, velocity and air in the system are also essential. A minimum velocity of 5 ft/sec is necessary to ensure effective cleaning action. Introducing air into the system provides slugging or turbulence and increases scouring action. The wash cycle should take 6-10 minutes. With longer times, the water becomes too cold. The concentration depends upon water hardness and iron content. Acid rinse. Rinse the line with acidified water (pH 3.0-4.0) to remove all traces of cleaning solution (2-3 minutes minimum contact time). This should be done after every milking. It helps prevent mineral deposits and the lower pH is bacteriostatic. All equipment and utensils should be stored in a manner that permits water to drain and equipment to air dry. In CIP systems, a drain should be located at the lowest point in the system. Teat cup liners and other rubber parts that come into contact with milk must also be thoroughly cleaned after each milking and sanitized before the next milking. Liners and other rubber parts should be replaced when they have been used for the recommended number of milkings (e.g., 1200) or when they become soft, cracked or rough, or have holes. Pores and cracks in rubber parts protect soil and microorganisms from effects of cleaning and sanitizing.
Bulk Milk Tanks
Bulk tanks also must be properly cleaned and sanitized, or psychrophilic bacteria (microorganisms capable of rapid growth at temperatures of 35 to 50°F) multiply rapidly. Tanks are cleaned by using essentially the same procedures as recommended for milking equipment. The milk hauler is normally responsible for rinsing the tank immediately after the milk is removed. Rinse water temperature should be 90-120°F. Following this, the tank must be washed, rinsed, and sanitized. Allow the mechanical cleaning device to operate until clean (6-10 min.). Cleaning solution temperature should remain above 120°F during the wash cycle and that means starting with hot water (170°F). Rinse the tank completely with tepid water, finishing the rinse with acidified solution as it neutralizes and removes detergent residues and removes inorganic soils. Tank covers and gaskets should be disassembled and the calibration rod removed for manual cleaning. The outlet connection and outlet valve must be cleaned manually. The tank exterior should be washed. Sanitizing should occur just before the next milking. Allow the sanitizer to drain from the outlet to prevent sanitizer residues in milk. Tanks may be cleaned manually or with CIP or mechanical systems.
CIP Equipment
The development of automatic (CIP) milking and bulk tank systems have been great time-savers for dairy farmers. However, these systems must be properly maintained. Many problems will occur if these systems are not checked regularly, at least twice-a-year.
Improper or careless cleaning and sanitizing of equipment and tanks is a major cause of inferior milk quality. It need not be if cleaning water and cleaning compounds are compatible and a precise procedure is formulated and followed.
