Functional Properties
Changes of water holding capacity (WHC) and oil holding capacity (OHC)
were determined according to the methods described by Choe et al. with
minor modifications [9]. The sample (1.0 g) was placed in
pre-weighed 25 mL centrifuge tubes and dispersed in 10 mL of distilled
water/soybean oil under magnetic stirring with occasional vortex
agitations for 10 min at room temperature. Afterwards, the samples were
centrifuged at 4000 × g for 15 min at ambient temperature. Then, the
centrifuge tube containing sediment was weighed. The WHC or OHC was
appraised as g water or oil per g dry sample, respectively.
The emulsifying capacity (EC) and emulsifying stability (ES) were
evaluated according to the described method of Di et al. with small
modifications [21]. Briefly, 5 mL of soybean oil and 5 mL of sample
solution (80 mg mL-1) was mixed. Then the mixture was
homogenized by a high-speed shearing blender (PT-10-35GT,
BUCHI Labortechnik
AG, Switzerland) at 10, 000 rpm for 2 min at room temperature and
centrifuged at 3000 ×g for 5 min at room temperature. The emulsion
formed was admitted to keep for some minutes until the emulsion layer
was stable. EC was calculated as follows Di et al:21
\(\text{EC\ }\left(\%\right)=\frac{H_{2}}{H_{1}}\times 100\) (2)
Where H1 was the total height of liquid, cm;
H2 was the height of the emulsified layer, cm.
The above emulsion was centrifuged again after heating at 80 °C for 30
min and then cooled at room temperature. ES was expressed by the
following equation Di et al [21]:
\(\text{ES\ }\left(\%\right)=\frac{H_{4}}{H_{3}}\times 100\) (3)
Where H3 was the total height of the liquid after
heating; cm; H4 was the height of emulsion layer after
heating, cm.
The foaming capacity (FC) and foaming stability (FS) were evaluated
according to the described method of Di et al. with small modifications
[21]. Sample solutions were prepared at 10 mg mL-1and pH of the phosphate buffer was adjusted to 7.0. The solutions were
whipped in graduated plastic tubes using a homogenizer (PT-10-35GT,
BUCHI Labortechnik
AG, Switzerland) at 10, 000 rpm for 3 min at room temperature. The
volume was recorded before and after whipping. FC and FS were reported
by the formula (4).
\(\text{FC\ }\left(\%\right)=\frac{V_{1}-V_{0}}{V_{0}}\times 100\)(4)
Where V0 represented the volume prior to homogenization,
mL; V1 represented the volume after homogenization, mL.
Following, the determination of FS was performed by a similar procedure
and the residual foam volume was measured after sample keeping for 30
min at ambient temperature. The formula (5) was applied to express the
FS value.
\(\text{FS\ }\left(\%\right)=\frac{V_{3}-V_{0}}{V_{0}}\times 100\)(5)
Where V3 represented the residual volume after standing,
mL.