Standard Plate Count (SPC): The SPC determines the total number of bacteria in a milk sample that can grow
and form countable colonies on Standard Methods Agar when incubated aerobically at 32°C (90°F) for 48 hours.
It serves as an overall microbial quality index. While the legal maximum for producer milk is 100,000/ml, ideally
SPC values should be less than 10,000/ml. Extremely high counts in raw milk (e.g., due to poor cooling) can
cause defects in raw milk that result in its rejection, due to off-odors and flavors such as sour, malty or rancid.
These and other microbial defects can carry over into products. The SPC is the reference method for other official
testing procedures. The Plate Loop Count (PLC), which plates a 1:1000 dilution, is a modification of the SPC.