In nearly all food, feed or fuel applications for a whey product, whole or fractionated, the first step in the process is to pass the whey through a centrifugal separator to recover as much of the milk fat as is possible prior to any further processing. If the whey is going to be field applied as a fertilizer the separation step is often not undertaken although it could be cost effective depending upon the volume of whey being dealt with. The absolute last resort would be to treat the whey as part of the wastewater stream from a facility. This allows for no cost recovery and adds substantial cost to the process related to the increase in both BOD and COD loads within the wastewater treatment system.
When field applying as a fertilizer the whey supplies Nitrogen from the protein, small amounts of Potassium and Phosphorus from the mineral portion. There is some moisture value for the crops but the lactose is generally providing minimal benefit. Care must be taken to not over apply whey, especially acid whey, to a field because of the overall increase in other minerals, which may detrimentally affect the soil. A good benchmark would be no greater than one inch total applied to a field per year, generally in increments of ¼ inch or less to limit the possibility of mineral deposits and ‘burning’ on the vegetation. Even at these levels if a small amount of salt whey is applied the irrigator runs the risk of elevating both the sodium and chloride levels in the soil above acceptable, healthy levels. This is yet another reason to consider further processing and recovery of the components where practically possible.
Related to fuel applications both sweet whey and acid whey can be utilized to provide a majority of the make-up moisture and a portion of the fermentable carbohydrate to the initial mash prior to addition of microflora to produce fuel alcohol. In some instances the initial pH of the mash might require adjustment to promote the most effective and efficient growth of the microflora. This pH adjustment might also be affected by the buffering capacity of the minerals present in the whey. When used in this manner the value of the whey is derived principally from the fermentation substrate provided via the lactose, however, the protein is contributing very little toward the production of fuel alcohol. The recovered value of the protein could be in a slight elevation of the overall protein value of the distillers’ grains when used as an animal feed.
The food and feed uses for whey components sometimes overlap. An operation might utilize ultrafiltration to fractionate the proteins away from the remainder of the solution and further process the proteins for food application and process the remaining lactose and mineral solution toward animal feed. This is just one of many potential scenarios possible once the initial serum begins the process of fractionation. A partial listing of the potential food grade products that can be obtained from whey include: whey cream, sweet whey, acid whey, whey protein concentrate (WPC) – 34, WPC-50, WPC-80, Whey Protein Isolate, Lactose, reduced lactose whey, reduced mineral whey and specialty fractions made to order for functionally specific uses. Most of these products will be concentrated and dried for maximum stability but some may be utilized in liquid form.
The many fractions obtainable from whey are principally made possible through the advent of membrane separation technologies that permit the splitting of the initial solution into two or more distinct products based on molecular weights of the material. The tighter the membrane, the smaller the molecular weight of the compound that will be allowed to permeate and the greater the quantity of the solution that is retained. By engaging in the use of ultrafiltration, microfiltration, nanofiltration and reverse osmosis membranes of differing molecular weight cutoff (measured in Kilo Daltons – KD) the initial solution can be progressively fractionated into very specific products with differing functional characteristics. The more specific the fraction and its’ resultant uses, the greater the value that can be added to the initial starting material. The refinement of technologies revolving around these fractionation processes is one of the current areas of great focus in dairy product research.
Whey products are generally marketed in dry form to maximize stability and shelf-life of the product. In some cases the drying process may induce some alterations in the functionality of the final product. However, these changes can generally be overcome and are considered an acceptable trade for a stable product with an extended useful lifespan. These dry products are readily transported, without refrigeration, both domestically and internationally with minimal storage cost because they may be transported and stored at ambient temperatures.