Quaternary ammonium compounds (QACs) are surface-active substances often used as disinfectants. They are also used as biocides, pesticides, and as additives for technical applications.
QACs have the basic structure NR4+. Those possessing R groups with long alkyl chains are known to be especially effective as antimicrobial agents and particularly useful for the disinfection of containers and surfaces. This is especially relevant in the milk industry, as QACs are typically used to disinfect the insides of tanks used for transporting milk from farms to processing plants. If significant QAC residues are left behind after tank disinfection, allowing these compounds to leach into the milk and, ultimately, getting into the store-bought milk supplies at levels compromising personal health. Recent data points to nearly 12 percent of all monitored milk to be tainted with QACs. The primary QACs that may be found in milk are benzyldimethyldodecylammonium chloride (BAC 12), benzyldimethyltetradecylammonium chloride (BAC 14), benzyldimethylhexadecyl ammonium chloride (BAC 16), and didecyldimethylammonium chloride (DDAC).