b-Lactoglobulin Aggregates from Heating with Charged Cosolutes: Formation, Characterization and Foaming - Food Colloids: Self-Assembly and Material Science - page 190

in the foam when b-LG aggregates were generated in presence of cosolutes
(data not shown). This initial number of bubbles levelled off at C cs *, and it was
identical whatever cosolute used. This result can be interpreted in terms of
similar interfacial properties of the soluble aggregates that were present. The
foams stabilized with aggregates generated with cosolutes exhibited signifi-
cantly lower drainage rates as compared to b-LG alone. Figure 8 shows the
variation of the normalized liquid fraction for the two foam heights of 6.5 and
11.5 cm. It can be seen that, in presence of cosolutes, aggregates are able to
retain much more liquid within the thin films and Plateau borders, as the
drainage rate exponent is two threefold lower than that of foams stabilized by
aggregates of b-LG heated alone. This behaviour can be directly linked to the
increased surface viscosity that was reported previously 39 in combination with
the high surface elasticity. Hence it has been shown that, in the case of the
interface-dominated drainage regime, because of the high surface elasticity
compared to bulk, the liquid fraction scaling exponent is close to 1, whereas it
reaches much higher values ( 3to 4) if the drainage is limited by the bulk. 40

1

A

-1.06

0.1

-2.9

6.5 cm

0.01

1

B

-1.4

0.1

-4.0

11.5 c 11.5 cm

0.01

100 1000 10000

Time [s]

Figure 8 Normalized liquid fraction in the foam versus time for solutions heated at pH 7.0
and 801C for 10 min (protein concentration 10 g L 1 , arginine HCl concentra-
tion 0-70 mM). The quantity e 0 is defined as the liquid fraction at the end of N 2
sparging at two height positions in the foam: A, 6.5 cm; B, 11.5 cm. The arrow
indicates increasing cosolute concentration up to C cs