31 Pa. Stat. § 700j-606
Milk dealers buying or receiving milk from producers on the basis of, or with reference to, the amount or percentage of butterfat contained in such milk, as determined by the method commonly known as the "Babcock Test," shall make such test at least once every sixteen (16) days. The milk from each producer shall be represented by a composite sample taken from the entire delivery of each of the several lots of milk bought or received from said person, and shall cover a period of not more than sixteen (16) days. The composite sample, to which a suitable preservative has been added, shall be made up of aliquot parts taken from each of the several lots of milk from each producer concerned, and composite samples of all producers concerned shall cover the same period of time.
Any person taking a sample or samples of milk, either from the aliquot part of each lot of milk sampled or from the composite lot of milk sampled, shall thoroughly stir or mix the contents of each and every container immediately before such sample or samples are taken, in such manner that the milk is thoroughly mixed in each container before the sample is taken. No weigh tank or container from which the aliquot part is taken for composite samples shall have any partition, division, or strainer which will prevent such thorough stirring or mixing. Each composite sample shall be held in an airtight bottle, such bottle being plainly labeled showing the name or number of the producer whose milk the composite sample represents, and the rack or container where the samples are held shall be plainly labeled showing the date of the first and last day of the period covered by the said composite samples.
The board may require that the composite samples be tested at the receiving station where the milk is received, or by a licensed laboratory, within five days from the end of the period when the composite samples were taken. After such samples have been tested, their residues shall be held intact and in condition suitable to test on the premises where they are tested, for a further period of not less than ten (10) days after the rendering of a statement to the producer for milk delivered during such period, in order to make possible a check test.
Every milk dealer affected by the provisions of this act shall, within two (2) days after the day on which the test herein provided for has been made, notify the producer or his agent of the result of such test, stating the period of time during which said composite samples were taken. Notice under this section shall be given by posting of the results of said tests continuously for ten (10) days in a conspicuous place in the plant or receiving station, or in writing delivered to the producer or his agent. Where a daily test is made on milk, and the average of these several tests is used as a basis of settlement, there shall also be a composite sample taken covering the period of the first half of the month, and a composite sample taken covering the period of the last half of the month, and such samples shall be held intact on the premises for a period of not less than ten (10) days after the rendering of a statement to the producers for milk delivered during each such period, in order to make possible a check test.
The board shall make check tests, and other reasonable tests, whenever in its judgment such tests are advisable for the public welfare, and may also require additional samples or additional composite samples from time to time. In addition, the board may require by regulation tests and testing procedures for components other than butterfat.
31 P.S. § 700j-606