Whey Protein Concentrates

There has been a continuous increase in the production of whey protein concentrates (WPC) since the introduction of the latest ultrafiltration process about three decades ago. It is now a major means of WPC production throughout most of the dairy countries of the world. Increased production of WPC warrants its greater application in food products. Though soluble WPC have been found to be technically suited to a wide range of products, its use is not cost effective in all cases. Presently, WPC constitutes a very small proportion (10%) of protein utilisation in food industry. The largest potential use of WPC is as a replacement for non-fat dry milk (NFDM) in the food industry. WPC with 35% protein is perceived to be a universal substitute for NFDM, because of the similarity in gross composition and its dairy character.Superiority of WPC over NFDM is also due to cost advantage.Due to various reasons, buffalo and cow milks are being humanised and used partly or exclusively for feeding human infants throughout the world. For humanisation,apart from making other modifications, whey proteins proportion needs to be increased in these milks. For this, a great potential lies in the application of WPC.WPC can also be seen competing as protein and functional ingredient with casein,egg albumin and soya proteins for use in food products. The PER value of whey proteins (3.2) is very high compared to standard casein (2.5).

i. Manufacture of Whey Protein Concentrates

Procedures for the manufacture of whey protein products are based on known behaviour of whey components under defined conditions. Properties that have been exploited commercially include: molecular size differences (Ultrafiltration, gel filtration), insolubility of protein at high temperature, charge characteristics (demineralization, protein removal by ion exchange), aggregation by polyphosphates, and crystallization of lactose.

i) Ultrfiltration Process: By 1981, Ultrafiltration (UF) had become the most widely used process for recovery of soluble whey protein concentrate (WPC).The development of robust, synthetic and cleanable membranes and the refinement of continuous operation using multi-stage, recycle loops, and diafiltration have been significant factors contributing to the success of this process.With this process, a highly functional WPC is produced for a wide variety of applications.

ii) Gel Filtration Process: This process has been used commercially for recovery of WPC. The hydrated gel acts as a molecular sieve in that small molecular weight components are able to enter the solvent phase within the gel beads.Protein molecules remain in the solvent phase surrounding the beads. High and low molecular weight fractions then can be recovered. Products of 30 to 80% protein can be manufactured. The process is expensive to install and operate,and the yield, at 65% of the proteins in whey, is low. It also is subject to fouling and microbial contamination. It is no longer used in commercial operation.

iii) Heat precipitation process: Whey proteins may be precipitated with heating of whey at acid or near-neutral pH. Acid whey must be heated to at least 90oC and maintained at such temperatures for at least 10 min to achieve maximum yields. For sweet whey’s, good yields can be obtained by heating at pH between 6.0 and 6.5, although products so derived have higher mineral concentrations than those of acid whey unless pH is adjusted to 4.6 prior to protein removal.

The precipitate so formed is firmer and more readily separated than that formed in non-acidified whey. precipitated protein is removed by settling (static or accelerated), washed, re-separated, and dried. In modern plants, high-speed centrifuges such as clarifiers and decanters are used for separation. The product is dried using ring, fluid bed, roller or spray driers. Typical yield of whey proteins by this process is 4.2 to 5.2 kg/m3.

 

                            Protein yieldsa and concentrations of principal classes of dried

whey protein products

a Expressed as precentage of (total-nonprotein N) X 6.38 in original whey.

b Ultrafiltration, UF; gel filtration, GF

c Regenerated cellulose, cell; silica, sil. Pilot-scale data only.

d Lactose, Lac; Minerals, Min.

e Whey protein concentrate, WPC; delactosed whey, DLW; demineralized whey,

DMW; delactosed, demineralized whey, DLDMW.

 Percentage composition of whey protein concentrates

 Process refinements include demineralization prior to heating, pre-concentration by reverse osmosis and Ultrafiltration, and continuous, high temperature reaction (120°C for 8 min at pH 6). Most processes result in an insoluble product, but through heating whey to 95oC at pH 2.5 to 3.5, then adjusting to pH 4.5 prior to separation,it has been claimed that a product soluble at pH 5 can be produced.

iv) Precipitation by complexing agents: This process is also called the cold precipitation process. Numerous complexing agents can be used to recover protein from whey; of these, polyphosphates appear to be the only group to be used commercially for this purpose. Long-chain polyphosphates precipitate protein from whey at low pH e.g., 3.5. Typically, potassium polymetaphosphate and sodium hexametaphosphate are used. The precipitates so formed are removed by centrifugation, washed, and then subjected to pH alteration and calcium addition to remove the phosphate. Removal of calcium prior to phosphate addition reduces the amount of phosphate required and results in recovery of up to 90% of the original whey proteins. Further modification of this process is also possible.