3.1.2. Visual appearance and lightness
The visual appearance of both non-homogenized and homogenized
systems was also determined after 24 h storage at ambient temperature.
All systems had creamy whitish color in appearance similar to
reconstituted milk powder solutions (Fig. 2 inset). After 24 h observed
in all non-homogenized systems while the homogenized systems
were visibly stable. The overall results demonstrate that high-pressure
homogenization broke down the large protein aggregates and led to
an even distribution of protein particles thereby producing more stable
systems during storage.
The lightness of the systems was also measured. Fig. 2 shows that
the homogenized systems had higher lightness (by about 1 unit)
(p N 0.05) than the non-homogenized systems at 1 to 10% MWP. The
higher lightness could be due to the smaller average particle diameter
produced leading to more efficient light scattering (McClements,
2002). Fig. 2 also shows that the lightness of both systems increased
with increasing protein concentration. The lightness increased steeply
from 0 to 5% protein, and then increased more gradually at higher protein
concentrations, with a lightness of around L* = 88 being obtained
at 20% protein. A similar trend was observed in oil-in-water emulsions
stabilized bywhey protein isolate,where the lightness increased steeply
from 0 to 5% oil, and then increased more gradually at higher fat contents,
eventually reaching a value of L* = 95 at 20% oil (Chung et al.,
2012). The high lightness achieved suggests that the protein particles
have potential to confer lightness (whiteness) to reduced calorie sauces
after some of the fat droplets (or starch granules) are removed.