Lactose-Free Milk Is More Prone To Long-Term Souring

Although milk isn’t meant to last forever, certain boxed versions of the beverage can remain fresh for months after rapid sterilization at ultrahigh temperature (UHT). The process isn’t perfect, however, because it can spur browning chemistry known as the Maillard reaction, as well as other processes that degrade milk’s taste and quality. Food scientists are now reporting that milk with hydrolyzed lactose made for the lactose intolerant is even more susceptible to chemical deterioration during long-term storage (J. Agric. Food Chem. 2014, DOI: 10.1021/jf501671z). Researchers have suspected that the lactase enzyme and atypical sugar content in lactose-hydrolyzed milk might give rise to unwanted side reactions. Hanne C. Bertram of Aarhus University in Denmark teamed with scientists at Arla Foods, a major Scandinavian dairy producer, to analyze chemical changes in lactose-hydrolyzed UHT milk samples compared with regular UHT milk. Sure enough, over a nine-month period the lactose-hydrolyzed milk formed more furosine—a calling card for the Maillard reaction—as well as more fatty acid oxidation products such as 2-pentanone and more free amino acids.