Carryover

Unintentional transfer of substances between processes or products

Carryover is the transfer of substances (product residues, microbes, cleaning agents, etc.) from one process or product to another, most commonly from inadequately cleaned equipment surface areas. In terms of product to product carry over the most applicable use of the term is the maximum allowable carryover (MAC or MACO) which is defined in PDA TR29, Points to Consider for Cleaning Validation, as "the total amount of target residue allowed in a batch of the next manufactured product" more simply, how much of product A can carryover into product B. PDA TR29 provides the methodology to calculate the MACO.