Lactose containing dairy co-products of cheese manufacturing are generally low value. The development of value-added products, such as prebiotic dietary fiber, is desirable. We have successfully polymerized mixtures of lactose and glucose into polylactose via extrusion using citric acid as a catalyst. The effects of extruder feed rate, citric acid concentrations, and the concentration of glucose have been evaluated for their effects on fiber yield, and extruder parameters (SME, motor torque, temperature). Product was extruded on a Buhler twin-screw 44mm twin-screw extruder. Process (temperature, motor torque and specific mechanical energy (SME)) and product (color, dietary fiber, degree of polymerization (DP), residual lactose and hydroxymethylfurfural (HMF)) responses were measured in response to the formula and process change. Generally, higher feed rates resulted in lower SME and higher motor torque. Higher feed rates resulted in less brown color, and more residual lactose and glucose. The citric acid catalyst concentration effects were more pronounced at a lower feed rate and higher concentrations lead to more brown color. Residual lactose decreased with higher citric acid concentrations. Surprisingly, brown color did not correlate with higher HMF concentrations but did correlate with higher temperatures in the early portion of the extruder and with SME. HMF can be removed via carbon filtration. The cleaned-up fiber material is currently being evaluated to see if it has prebiotic activity in rats, and this could pave the way for the generation of soluble fiber from lower-cost lactose-containing dairy co-products via a continuous process.

Polymerization of sugars by reactive twin-screw extrusion to produce soluble fibers for food and feed

253rd National Meeting (2017)

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