Whey Protein Concentrates And Their Functional Properties By Kathirvelu Thenmozhi At Isnare.com Ezine Articles

Whey Protein Concentrates (WPC) are nothing but powders made by drying the retentates from ultrafiltration (UF) of whey. They are described in terms of their protein concentration, protein content as percentage of dry matter, which ranges from 25 to 80%. To obtain a 35% protein-containing product, the liquid whey has to be concentrated to about 5 fold, which has a total solid of 8%. Concentration by ultrafiltration to a level of 25 to 30 fold is required to obtain 80% protein in the WPC with a total solids content of 25%.

What are functional properties?

The functional properties are defined as those properties, which determine the overall behavior of proteins in foods during production, processing, storage and consumption. Whey proteins have two types of properties viz. nutritional and functional. As for as nutritional attributes are concerned, the whey protein concentrates are rich in essential amino acids such as lysine, tryptophan, cystine, and methionine enabling its use in infant food and aged people diet as well as in enrichment of cereals. Whey proteins are known for their high solubility over a wide range of pH, (lower the pH, higher the solubility), better aeration properties, ability to form gels at high temperature, and better water and fat binding properties.

The important functional properties of the whey protein concentrates can be listed as follows.

Water solubility

The solubility of whey protein is considered as the most important one because it affects the other functional properties like gelling, foaming, and emulsifying properties. When the temperature increases, the solubility of whey protein is lost since they are heat sensitive. Among them, the immunoglobulins are more sensitive as they are denatured at a temperature of 70°C followed by alpha lactalbumin, beta lactoglobulin and serum albumin resists temperatures up to 100°C.

The proteose-peptone component is the most heat resistant among the entire whey protein component. Denaturation by heat is nothing but breakage of sulphur bridge within the molecule resulting in unfolding and insolubility. The insolubility reaches its maximum at a pH of 4 but even at this level, the solubility is around 60%.

Water absorbing capacity

The maximum water absorption by the whey protein concentrate occurs when the exposure is between 5-10 min. But sodium caseinate and soy protein isolates are capable of absorbing water better than the whey protein concentrates. Water absorption is least affected by change in pH, salt concentration but heating generally favours especially when the temperature is around 80°C. This property can be utilized in baking industry.

Gel forming ability

Unfolding of protein chains coupled with exposure of amino acids result in gel formation. This is due to the formation of hydrogen ionic bonds. When protein chains are linked by the hydrogen bonds, cavities are formed in them absorbing water and the structure formed is a network of three dimension encircling pockets of water. Heating causes the unfolding and higher the temperature, the gel formed is stronger. If 80% concentrated WPC is heated, gel formation can be noticed on cooling.

Foaming ability

Foaming is nothing but the incorporation of air to form a stable structure. Formation of foam depends on partial unfolding of protein chains at the air-liquid interface. Denatured whey proteins have poor whipping properties and to have a better whipping property, severe heat treatment of whey proteins should be avoided. But mild heat treatment tends to favour or improve the whipping ability of the whey proteins.

Foaming ability can be measured by whipping time, over run and foam stability. The highest over run is obtained when the whey protein is at its highest solubility in which there will be mild but not zero denaturation. The whey protein concentrate is a better substitute for egg white, the use of which in food is objected to by strict vegetarians.

Emulsifying ability

The surface properties of the whey proteins make them good emulsifying agents. The surface properties also govern the foaming and whipping qualities due to reduction in the interfacial tension between the hydrophilic and hydrophobic components in the food. This property is common in foods rich in fat and water. Emulsifying capacity may be defined as the amount of oil, which can be emulsified, by certain quantity of protein prior to phase inversion or collapse of the emulsion.

Emulsion stability is defined as the ability of the protein to form an emulsion, which remains unaltered over a given period and conditions. The emulsifying ability or capacity directly depends on the solubility of the whey protein. Hence the factors that affect the solubility in turn regulate the emulsion formation.

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