Summary Continuing problems with post-pasteurization contamination of milk and cream have stimulated dairy plants to undertake intensive programs to improve sanitation practices. Sources of contamination such as air, water, containers, fillers, pumps, joints, valves, cleaners and sanitizers have received more attention by the more progressive plants. Basic steps have been found to be necessary for improved keeping quality. These are a standardized reference test such as the Moseley 5 days at 45 F test, application of trouble shooting procedures, and application of additional sanitary measures. Comparisons using the Moseley keeping quality test and CVT test showed little correlation between them. A newly designed sampler has provided means of monitoring sanitary conditions and product keeping quality. It is a 3/8-inch drilled hole with a rubber insert clamped in by a stainless steel clamp. The sampler has withstood any pressure applied to it internally under normal dairy processing and can be permanently located in any pipe line system. Product filling equipment is still the main contributor of contamination. It was found that manual cleaning instead of CIP cleaning was a necessity in equipment that had many product sealing joints. These areas particularly vulnerable due to heavy lubricants often used. Spraying filling areas with sanitizers during processing is essential. Plant conditions change every hour during production, therefore, adjustments in procedures to avoid contamination must be exercised. Cursory examination of plants to evaluate sanitation is insufficient. The best criterion still is the bacteriological and flavor condition of the product at the consumer level.
Summary A study was made showing relationship between post-pasteurization contamination of milk and cream and increase in bacterial count of bottled and paper carton products during storage at 45 F for 5 days. A survey indicated extensive post-pasteurization contamination in plants not employing this type of keeping quality test. The 5-day at 45 F test was more sensitive than the coliform test in detecting post pasteurization contamination. Excessive numbers of thermoduric bacteria in the raw supply also were detected by this method when plant equipment was properly cleaned and sanitized. Special in-line sampling techniques were developed to determine source of contamination. One procedure employed sterile disposable hypodermic syringes inserted through rubber stoppered nipples welded into lines at different locations in the system. Another technique involved removal of samples by insertion of sterile disposable hypodermic syringes through rubber or neoprene gaskets between joints in different locations in the plant. Bottle and paper carton filler equipment offered special cleaning and sanitizing problems and suggestions were made on steps to minimize contamination from these sources. Application of the 5-day at 45 F keeping quality test followed by careful study of contamination sources has greatly improved shelf life of pasteurized fluid milk and cream and has represented a real economic advantage to plants adopting the program.