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Using Membrane Filtration Techniques to Fractionate Acid Whey into Value Added Ingredients
There has been a huge expansion in acid whey production due to the rapid growth in Greek yogurt manufacture, therefore it is critical to find an environmentally friendly and economically feasible way to process acid whey. Membrane filtration techniques have been used for many decades in the dairy industry to fractionate components into different streams. Objective of this study was to determine the suitability of nanofiltration (NF) membranes for fractionating acid whey into value added streams that could potentially be used in food products. Because of the relatively low protein content of Greek yogurt acid whey, our research focused on possible value added components in the UF permeate of acid whey. Potential end products include lactose, lactic acid, dairy minerals, peptides and oligosaccharides. Our initial focus was on reducing the calcium and lactic acid content of this UF permeate. Approximately 1,000 liters of acid whey was obtained from a Greek yogurt manufacturer for each trial. A 10,000 daltons UF membrane was used to fractionate the protein. The UF permeate was then processed by one of two different NF membranes. An experimental NF membrane was evaluated for divalent ion permeation and compared to a control NF membrane. Permeates were concentrated to 1X and 2X, and was sampled at 1380, 2760 and 4140 kPa processing pressures, and at temperatures: 4, 21, 43 and 54⁰C. Flux also was recorded. Total solids, lactose, galactose, lactic acid and calcium were determined. Higher temperatures and higher pressures yielded higher rates of component permeation for each membrane. The experimental NF membrane had higher permeation on all analyzed components compared to control NF membrane. Lactose and calcium were permeated on the experimental NF membrane, in contrast to the control NF membrane. By utilizing various membranes with very different permeation properties, fractionated products could potentially be achieved. We are exploring other membranes to evaluate the potential creation of purified value added fractions from acid whey.
Keywords: Acid Whey, Membrane Processing, Nanofiltration