EFFECTS OF IONIC STRENGTH ON THE FOAMING PROPERTIES OF WHEY PROTEIN ISOLATE AND EGG WHITE IN THE PRESENCE OF POLYSACCHARIDES

ABSTRACT The effect of ionic strength on the foaming properties of whey protein isolate (WPI) and egg white (EW) proteins was investigated in protein–polysaccharide mixtures in the presence of NaCl and pectin/guar gum. Foaming properties were assessed based on the total foam volume produced and foam stability as the time required for the collapse of the foam to half of its initial foam volume. The foam volume and stability of WPI significantly (P < 0.05) increased when NaCl concentration rose from 0 to 0.05 M, and decreased with further increase with and without polysaccharides. Initial increase in salt concentration up to 0.03 M improved both foam volume and stability of EW solutions with and without polysaccharides. Further increase in salt concentration progressively reduced the foaming properties of EW. Foam volume of both WPI and EW decreased with the addition of polysaccharides. However, the addition of polysaccharide had a significant effect (P < 0.05) on foam stability. PRACTICAL APPLICATIONS Food dispersions often take the form of emulsions and foams. Whey protein isolate (WPI) and egg white (EW) proteins are extensively utilized foaming agents in the food industry. Stability is an important property of food dispersions, since consumer perception of quality is influenced by appearance and would be controlled by the addition of polysaccharides. Real food systems very often contain a mixture of proteins and other ingredients such as sugars, salt, etc. The addition of such molecules may affect the functionality of proteins, which may result in gain or loss of handling properties. However, there has been limited reported work on the effect of ionic strength on the foaming properties of WPI and EW in the presence of polysaccharides. To overcome this inadequacy, in this study, the effect of ionic strength on the foaming properties of proteins in the presence of an ionic and a neutral polysaccharide was investigated. Results showed that the addition of salt up to a certain level enhanced foam stability, both in the absence and presence of polysaccharides, while further increase in salt concentration decreased stability. Therefore, the ionic strength or salt concentration in food foam would be determined carefully to have good stability during storage.