A Standard Plate Count in milk quality refers to which of the following?

• A. A number that should be less than 300,000 at the farm level per PMO regulations
• B. The total number of aerobic bacteria present in the milk at the time of pickup
• C. A number that is increased when milking machine cleaning is poor
• D. The total number of coliform bacteria present in the milk at the time of pickup

Answer: (B)

The Standard Plate Count is a measure of the total viable aerobic bacteria in a milk sample. It is obtained by plating a known volume on a general growth medium and counting the colonies that form under standard incubation, giving a CFU per milliliter value. This count serves as an overall indicator of milk quality and hygiene—the higher the SPC, the greater the bacterial load and the poorer the handling or sanitation conditions, up to the time of pickup. While regulatory thresholds (such as a value like 300,000) may appear in certain programs, they are specific standards and not what the test inherently measures. Saying it increases when milking machine cleaning is poor describes a consequence of poor cleaning, not the definition of the test. Coliform counts, by contrast, measure a subset of bacteria related to contamination, not the broad total captured by the SPC.