Investigation of Purification of Oligosaccharides Produced Using Twin-Screw Extrusion

Abstract

Lactose, a low value dairy product, was polymerized to a soluble dietary fiber called polylactose using twin-screw extrusion. Non- enzymatic browning reactions occurring during extrusion produce colored compounds and hydroxymethylfurfural. Thisresearch focuses on development and optimization of a purification method for polylactose using activated carbon and resins. Polylactose was ground, solubilized in water at three different concentrations (50 mg/mL, 100 mg/mL and 150 mg/mL). Forty mL of polylactose solution was flowed through the filtration system utilizing gravity. The filtration system was rinsed with 20 mL double distilled water. The rinse water plus the filtrate collected were freeze dried to achieve a powder form suitable for different analysis. 42.4% Purolite A874 resin followed by 42.4% Activated carbon and 3% diatomaceous earth was proven to have the best purification results increasing dietary fiber content from 54.48% to 92.24% while reducing the hydroxymethylfurfural content by 90.91% to a level that was lower than the maximum level determined by the Joint FAO/WHO Expert Committee on Food Additives HMF limit in polydextrose (0.1%). Furthermore, the effect of polylactose solution concentration for filtering 40 mL polylactose solution was determined. Using 50 mg/mL concentration achieved the highest dietary fiber content. This could be since less polylactose had to interact with the same amount of filtration material resulting in removing more impurities and caramelization products. However, the hydroxymethylfurfural content reduction was the same for 50 mg/mL and 100 mg/mL concentrations.