LACTOSE HYDROLYSIS IN DIFFERENT SOLIDS CONTENT WHEY AND MILK PERMEATES

Dairy permeates contain almost original amount of lactose, small fraction of other solid compounds and water. For complete lactose hydrolysis and glucose-galactose syrup production, it is essential to ensure the optimal substrate concentration and conditions to improve product quality and save energy, water and material costs. The aim of this study was to investigate beta-galactosidase preparates capability using concentrated whey and milk permeates with 20, 30 and 40% (w w(-1)) of total solids. Commercial beta-galactosidase preparates (Ha-Lactase 5200 produced by Kluyveromyces lactis and NOLA Fit5500 produced by Bacillus licheniformis, Chr.HANSEN; GODO-YNL2 produced by Kluyveromyces lactis, Danisco, Denmark) at dosage 500 NLU.L-1 (Ha-Lactase 5200, GODO-YNL2) and 500 BLU.L-1 (NOLA Fit5500) were used for lactose hydrolysis. The concentration of each permeate was 20, 30 and 40% (w w(-1)) of total solids. 10% KOH was used to adjust optimal pH for fermentation media. Samples were monitored in incubator for 4 hours at temperature 42.5 +/- 0.5 degrees C. Lactose, glucose and galactose concentrations were determined by HPLC (Shimadzu LC-20 Prominence, USA). Ha-Lactase 5200 preparate was able to increase lactose hydrolysis rate more than 90% in all permeates at 20% and 30% solids concentration. GODO-YNL2 preparate showed the highest conversion of glucose in sweet whey permeate at 20% solids concentration and the lowest conversion of galactose in sweet whey permeate at 30% solids concentration. The results indicated that substrate type and solids concentration have an effect on the relative activity of commercial enzymes. The study results give a greater understanding about permeates suitability for glucose-galactose syrup production.