Maillard Reaction Progression During Storage of Lactose Free Milk Powder Formulated with Maltodextrin and Ultrafiltration Permeate

Lactose-free milk powders (LFMPs) are susceptible to the Maillard reaction during storage because enzymatic lactose hydrolysis generates reactive reducing sugars, glucose and galactose. This study evaluated storage induced Maillard reaction progression in LFMPs produced through an optimized process integrating ultrafiltration (UF), UF permeate recombination, maltodextrin addition, enzymatic lactose hydrolysis, and spray drying. Skim milk was ultrafiltered to obtain a protein-rich retentate, then recombined with UF permeate and incorporated with 5% maltodextrin before β-galactosidase-mediated lactose hydrolysis to achieve complete lactose removal (<0.1% residual lactose) and facilitate spray drying. Three formulations were prepared: control (without UF permeate recombination or maltodextrin), UF (with UF permeate recombination but without maltodextrin), and optimized (with UF permeate recombination and 5% maltodextrin). Glass transition temperature (Tg) was determined by differential scanning calorimetry, and powders were stored at 30°C for 180 days. Maillard reaction progression was monitored using furosine (early-stage marker), 5-hydroxymethylfurfural (HMF) (intermediate-stage marker), available lysine (nutritional damage marker), and carboxymethyl lysine (CML) (advanced glycation end product).

The optimized formulation exhibited a significantly higher Tg (51.30°C) than the control (28.36°C) and UF (29.92°C) formulations. Between Day 0 and Day 180, furosine increased from 201.24 to 1017.24 mg/100 g protein in the optimized formulation compared with 499.84 to 1716.32 mg/100 g protein in the control and 304.32 to 1651.45 mg/100 g protein in the UF formulation. Likewise, HMF increased from 43.53 to 79.13 μmol/L in the optimized formulation, whereas the control and UF formulations increased from 62.80 to 243.65 μmol/L and 44.51 to 242.19 μmol/L, respectively. Available lysine loss after 180 days was limited to 20.93% in the optimized formulation compared with 41.90% and 47.72% in the control and UF formulations, respectively. The optimized formulation also exhibited the lowest CML concentration (194.31 mg/kg protein). The higher Tg of the optimized formulation effectively retarded the progression of the Maillard reaction from early to advanced stages, thereby preserving the nutritional quality of lactose-free milk powder during ambient storage.