4. Whey pretreatment

Although whey from different sources vary, there are tools available to pretreat the whey prior to fermentation and distillation. Traditionally, whey clarifiers are used to remove casein fines while whey separators are used to remove whey cream. This leaves behind non-fermentable substrates such as whey proteins, minerals, and acids, which do not contribute to the production of distilled beverages. Although whey proteins are soluble, they may precipitate when exposed to heat during pasteurization or during distillation, which could interfere with operation of the still. Therefore, some method of protein removal, such as ultrafiltration, would be beneficial prior to fermentation. Removal of other potentially interfering compounds such as minerals and acids could be achieved through nanofiltration. Nanofiltration has the additional advantage of concentrating lactose to increase the concentration of fermentable substrate within whey, which would essentially improve fermentation and distillation efficiencies. It is important to note that these unit operations are expensive and resource intensive and therefore not likely to be used in artisan dairy processing. Nevertheless, membrane units are utilized in some specialty cheese facilities and could therefore be a relevant option.

### 5. Whey to commercial spirit

The Carbery method is the industrial method used to convert whey/whey permeate to ethanol [8, 9]. The method is similar to other industrial ethanol production processes in that a microbial fermentation is performed to convert sugars within a substrate to ethanol and an extractive distillation occurs to concentrate and separate the ethanol from other volatile compounds. Once distillation has occurred the spirit can be treated as any other distilled spirit for subsequent processing (Figure 2).

Figure 2. Process overview of spirit production via the Carbery method.

### Whey to Vodka DOI: http://dx.doi.org/10.5772/intechopen.81679

There are several key differences in the Carbery method when compared to traditional spirit production. Whey/whey permeate is readily fermentable and a sugar conversion step such as mashing or cooking is not necessary. Whey/whey permeate should arrive at the facility well above the optimum fermentation temperature and must be cooled before inoculation. The main fermentable sugar within whey is lactose, which cannot be utilized by Saccharomyces cerevisiae (S. cerevisiae), the yeast generally used for ethanol production. Kluyveromyces marxianus (K. marxianus), a lactose fermenting yeast is used to convert lactose to ethanol. The lactose levels within raw whey only allow for the production of a "beer" or "wash" with ethanol concentrations of 2–3% v/v. Whey permeate may be concentrated but ethanol production is limited by the sensitivity of K. marxianus to increased solute concentrations and ethanol. This low concentration of ethanol will increase the energy requirements during the distillation process. A beer still, extractive distillation unit and a rectifier are used during the extractive distillation process. A demethylizer is not employed during the extractive distillation process [8, 9] as very little methanol is formed during the fermentation process. The dilution, filtration, flavor additions, packaging, and distribution occur in a manner comparable to other spirits produced in a traditional manner.
