UTILIZATION OF WHEY

The whey constitutes a major ecological burden to be disposed of as a waste material because the biological oxygen demand (BOD) of whey is very high at 40,000 mg per kg. Utilization of this nutrient rich byproduct, which would otherwise go as a waste is predominantly favored due not only to the economic opportunities because of the nutrients but also from the disposal point of view.

How effectively the whey can be processed into useful products?

1. By simple removal of water by spray or roller drying to yield whey powder.
2. By increasing the ratio of protein in the end product through ultrafiltration in the manufacture of whey protein concentrate, processes involving fractionation in the manufacture of whey protein isolates and heat treatment to produce lactalbumin.
3. The processes that target the conservation of lactose in the whey by treating it with lactase, heat or acid and fermentation process to yield lactic acid, citric acid and single cell protein.
4. Electrolysis and ion exchange mechanisms to alter the mineral composition of the product.

If the whey is produced in factories in smaller quantities and the production is scattered, it is ideal to condense the whey using vacuum condensers and this method of reducing bulk is found to be economical and stored under deep freezing temperatures till use. The condensed whey can be easily transported to the central whey processing plant.

Manufacture of lactalbumin and whey protein isolates

The whey proteins can be easily denatured or destroyed and the aim is to separate the proteins without any detrimental effect so that they retain the functional properties. They are rich in protein content and very useful to the food industry. The manufacturing process involves use of non specific absorbent to bind the proteins in the whey, followed by elution of the proteins by treatment of the absorbent with a specific elutent. Carboxyl methyl cellulose and different variants of mineral oxides serve as absorbents.

Though the absorbents are relatively non specific, they show specificity to bind to certain proteins under set conditions of pH, ionic strength and temperature. These processes can be effectively utilized to produce protein isolates with a higher ratio of alpha lactalbumin to beta lactoglobulin than that present in whey. These two components hold big promise in the preparation of non allergic infant feeds.

Fermentation of whey

Biomass of yeasts can be successfully produced commercially through whey fermentation process. Commonly used yeast strains are Kluyveromyces marxianus var. lactis and Kluyveromyces marxianus var. marxianus. The famous “Bet fermentation process” in France is an example of this kind of fermentation.

Sweet whey is the choice for fermentation. It is first deproteinated and then diluted to a lactose concentration of 20-25 kgm-3. Since whey is limiting in nitrogen, ammonium salts are added to compensate the deficit along with certain trace metals like iron, copper, manganese and zinc to stimulate the yeast growth. The fermentation is continuous and it is operated at a dilution rate of 0.33 per hour and temperature of fermentation is set at 39°C. The mixing and aeration of the culture is continuous and the residual sugar level is 1 kgm-3. The biomass yield works out to 0.55 to 0.6 kg yeast on dry matter basis per kilogram of lactose metabolized and the biomass production is about 4.5 Kgm-3 per hour. 

The yeast is then separated and concentrated in a two stage washing cum centrifugation process and later plasmolyzed to make the yeast protein more accessible and finally dried and packed. The crude protein content of the biomass is 50% on dry matter basis and the only significant limitation is the sulfur containing amino acids. The value of protein is almost similar to casein and because of their functional properties, they are more sought after in baking industries, as a substitute for milk solids in the manufacture of yogurt, ice cream and other dairy products.