The composition of interfacial material from skim milk foams

Abstract

The foaming properties of skim milk vary with temperature of foaming in the range from 5 to 85°C, with foams of maximum stability being formed at approximately 45°C. This paper reports the significance of different milk fractions in the foam and concludes that the micellar casein fraction plays an important role in stabilization of milk foam formed at higher temperatures. This finding was supported by the fact that added calcium chloride increased and calcium-chelating agents decreased foam stability. These effects were attributed to the increase and decrease, respectively, in the amount of micellar casein in the milk. Furthermore, bubble ghost material sedimented by low-speed centrifugation of foam was found to contain predominantly caseins, and electron micrographs of foams formed at 45°C clearly showed casein micelles spread over the interface. However, other structures observed in the electron micrographs suggest that soluble milk proteins and possibly polar lipids are also present in the foams and play a role in formation of milk foams.

Comparison of Foaming Properties between Chelated Reconstituted SMP and Caseinates

“…Protein is considered to be excellent foaming agents based on their good adsorption toward the air-water interface, properties of steric stabilization and electrostatic stabilization, and their tendency to form structural coherence (Murray, 2007). It has been proved the that the major composition of milk foam is casein (Kamath et al, 2011).…”

“…An investigation carried out by Kamath (2011) Mohanty et al (1988) on the aspect of temperature where their work showed that 25º C is the minimum temperature for milk to foam, and 40º C is the optimum temperature; they also offered valuable data indicating that the fat content has a negative effect for milk to foam. Kamath et al (2008) explored the influence of temperature on the foaming properties of a variety of milk and concluded that 45º C is the most optimum temperature for the skim milk foam stability.…”

“…In contrast, the foam stability can be tested by determining the strength of the intermolecular bonds between the adsorbed protein and the cohesive viscoelastic film. Kamath et al (2011) tested foamability by checking how many millimeters of foam they could achieve out of 50 millimeters of sample solution with an airinjection method Foam stability was measured by recording the time it takes for the foam to reduce to half of its original volume.…”

“…Casein based foam usually has a size of 1 μm while the size of each casein submicelle is around 20 nm (Murray et al, 2004). Previous experimental results showed the the addition of calcium chloride is able to optimize the foam stability of milk since it enhanced the adsorption and aggregation of caseins (Kamath, 2011 Calcium phosphate is the compound that binds casein submicelles. Once the calcium is taken out from the system by chelating agents, the submicelles will fall apart.…”

“…Only a limited amount of research has been done for the examination how chelating reactions in milk will change the foaming properties. Kamath et al (2011) compared chelated reconstituted skim milk by between trisodium phosphate (TSC) and the non-chelated control samples at various temperatures; similar foamability and weaker foam stability were observed in the chelated samples at certain temperatures. The comparison of chelated milk and caseinate solutions remained to be examined.…”