The kinetics of aqueous lactose hydrolysis with sulfuric acid†

Abstract

Lactose-rich Greek yogurt acid whey (GAW) is a waste stream in the dairy industry that has caused severe environmental and economic challenges to the U.S. agricultural communities. Lactose is a sugar found in dairy products that has a low sweetness value and is often difficult to digest. Lactose can be hydrolyzed into glucose–galactose syrups (GGS). However, 5-hydroxymethylfurfural (HMF) is formed which must be removed for the GGS to be used as an alternative sustainable sweetener. In this study, we model lactose hydrolysis and include the first detailed kinetic investigation of HMF formation during sulfuric-acid-catalyzed lactose hydrolysis. We systematically examined the effects of temperature, lactose concentration, pH, and reaction time on the hydrolysis process, proposed 57 possible reaction networks, and developed a kinetic model accurately describing lactose hydrolysis and HMF formation, and calculated key kinetic parameters. Our model demonstrated strong alignment with experimental data and allowed us to simulate optimal conditions for maximizing GGS yield over 89% while minimizing HMF formation by 75–80%. This study provides valuable insights for optimizing reactor design and operational strategies, improving the economic viability and sustainability of GAW valorization.