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Fractionating 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. Acid whey is difficult to process for many reasons and whey from Greek yogurt manufacture is no exception. Traditionally, recovery of the whey protein has provided an economic incentive to process whey, however, Greek yogurt whey is especially low in protein as compared to other sources of acid whey and therefore it is more difficult to justify the expense of converting the whey into dairy ingredients as opposed to disposal. The objective of our research is to find economical methods to recover/convert the nonprotein components in Greek yogurt acid whey into value added ingredients.
Membrane filtration has been used for many decades in the dairy industry to fractionate components. Our focus is on reducing the calcium content of the UF permeate from Greek yogurt acid whey through the use of novel nanofiltration membranes. Calcium can interfere with production of ingredients such as crystalline lactose and hydrolyzed lactose syrups. Excessive calcium incorporation into the lactose crystal results in crystalline lactose that does not meet specifications for US food grade lactose and hydrolyzed lactose syrups with high mineral contents may taste salty.
Nanofiltration membranes traditionally are able to permeate monovalent ions like chloride, while retaining divalent ions such as calcium. The membranes evaluated in our study had been modified such that calcium also could permeate. Our results indicated lactose and calcium permeated the novel NF membranes to differing degrees as compared to the control NF membrane that did not permeate either component. Varying temperature, pressure and concentration of the starting permeate during NF resulted in changes in the relative permeation of lactose and calcium. Using a modified NF membrane we were able to concentrate permeate from Greek yogurt acid whey to approximately 25% total solids. A lactase enzyme with an acidic pH optimum then was added to produce a dairy syrup with enhanced sweetness and reduced salty flavor as compared to a control made with a traditional NF membrane. The ability to economically remove calcium from the UF permeate should enable processors to recover value from the permeate of products like Greek yogurt acid whey.
Keywords: Acid Whey, Membrane Processing, Nanofiltration