(730a) From Waste to Sweetness: Catalytic Strategies and Reaction Engineering for Upcycling Greek Yogurt Acid Whey

In the last decade, the dramatic rise in Greek yogurt's market share in the US has resulted in the production of about 1.8 million metric tons of byproducts Greek yogurt acid whey (GAW) annually. Managing GAW is challenging for the dairy industry due to the uneconomical processing costs stemming from its low protein and high mineral content. GAW is often disposed of in wastewater plants where the GAW's high biological (BOD₅) and chemical oxygen demands (COD) can overwhelm the system. There is a crucial need for innovative, sustainable methods to utilize GAW, reducing environmental impacts and improving agricultural and industrial use.

Our research team is developing a process to transform GAW into a glucose-galactose syrup (GGS). This process uses H2SO4-catalyzed hydrolysis of lactose into GGS. GGS has a similar sweetness to high fructose corn syrup. Undesired humins and 5-Hydroxymethylfurfural (HMF) are formed in this process. We develop a kinetic model that predicts the desired GGS production and undesired product formation. The kinetic model indicated that both glucose and galactose degrade into humins first and then humins can further be converted into HMF. Galactose has a higher rate of humin formation than glucose. We have designed and operated a pilot-scale reactor (227 L/hr) to achieve up to a 90% yield and selectivity of GGS with minimal byproduct formation based on the kinetic model. This pilot scale reactor allows us to make larger amounts of GGS that we are testing in a variety of products.

The GGS can be further converted into tagatose, a low-calorie sweetener that is 90% as sweet as sucrose but with 60% fewer calories. We developed an effective tagatose production process from GGS and described the chemistry of tagatose production.