Mo. Rev. Stat. § 196.560

Persons engaged in the purchase and sale of milk for manufacturing and processing shall keep receipts of sale and records of all such purchases of milk and cream for a period of at least one year. Records of such purchases shall include date received, weight, results of all tests to determine value or grade, and price paid. The state milk board * shall have access to these records all of which shall be kept confidential as to individual items or totals of an individual person or plant.