Challenges and prospects of turning lactose into lactulose through electro-activation: A comprehensive and critical review

Lactulose, a structural isomer of lactose, is a prebiotic disaccharide with significant pharmaceutical and nutritional benefits, is widely used in the food industry and healthcare as laxative, and in the preventing and treating portal-systemic encephalopathy. The conversion of lactose into lactulose is a sustainable approach to mitigating the environmental burden of whey while addressing lactose-related health concerns. Traditional methods of catalytic chemical and enzymatic isomerization have faced challenges such as low yields around 25 %, high costs, and environmental constraints; limiting their industrial feasibility or resulting in a costly product. In contrast, lactose isomerization by electro-activation (EA) has emerged as a promising and eco-friendly technology since lactose conversion yield >35 % is reported. The state-of-the-art of the EA lactose isomerization into lactulose and the interaction among the process parameters is thoroughly discussed in this review. However, despite its advantages, key challenges such as side products formation, colorization occurring during EA and relaxation time, as well as necessity of reaction yield enhancement have been addressed to highlight possible ways for EA process efficiency by combining EA with discolorizing techniques. Enhancing the process sustainability and energy efficiency through innovative technological advancements is crucial for improving the industrial use of EA in the process of lactose isomerization into lactulose. Moreover, the possibility of producing other valuable compounds, such as rare sugars and oligosaccharides, expands the industrial significance of EA lactose isomerization. The current review emphasized future research on optimizing process parameters and developing scalable strategies to improve yield, product color, cost-effectiveness, and industrial applicability, paving the way for a more sustainable and circular dairy industry.