Proteose peptone was isolated from thermally untreated whole cow milk using 12% trichloroaceticacid and washing several times with water, centri- fuged and dried. When the functional properties of proteose peptone was studied it had inhibitory effect against foam formation and that effect depend on the pH of the medium. The foam capacity was highest at the pH of 7.0 and the foam capacity decreased protein at the pH 5.5 and 8.5, respectively. Upon studying foam stability it appeared that the foam unstable after 30 minutes.
The acid pH was more effective in water absorption by proteose peptone than neutral and alkaline pH. Results showed that oil absorption rate was the highest at the alkaline pH=8.5 and the lowest oil absorption at acid pH=5.5. This indicate that the alkaline medium of the proteose peptone gave the best results in oil absorption and the acid medium gave the lowest results.
The effect of proteose peptone on emulsifying capacity and emulsion stability at different pH units was also studied. Results showed that the lowest emulsifying values were obtained at the acid pH=5.5 and increased to 23.67 ml/gm as the pH became 7.0 and the emulsifying vale reached to 25.50 ml/gm protein as the pH=8.5. Emulsion stability was studied within four days and the results showed that the emulsifying values decreased at all studied pH values, however, at pH 7.0 the emulsifying capacity was more stable than other pH values.The study of the effect of proteose peptone on gel strength at the different pH units indicate that the alkaline pH gave the highest gel strength followed by the neutral pH then the acid pH.
From the results it was obvious that the pH value had a significant effect on surface tension properties as it appeared that the acid pH gave the highest value while the neutral and alkaline pH vales caused a significant decrease in surface tension values. The decrease in surface tension values increased as proteose peptone addition increased.