Biomedical Engineering Reference
In-Depth Information
prepared from the O/W emulsion with a smaller median diameter of oil droplets was higher
because of the higher probability of interaction of the acid with the wall material within the
microcapsule [62]. The median diameter of the oil droplets in the emulsions prepared with
gum arabic or the soluble soybean polysaccharide was small, especially for arachidonoyl
ascorbate, which would be surface-active. This would also be a reason for the high oxidative
stability of the arachidonoyl ascorbate encapsulated with the polysaccharide.
Figure 21. Oxidation processes at 37
o
C and 12% relative humidity of (
) arachidonic acid without
ascorbic acid, (
U
) arachidonic acid in the presence of ascorbic acid and (
{
) arachidonoyl moiety of
arachidonoyl ascorbate in (a) nonencapsulated system, and in microcapsules prepared with (b)
maltodextrin, (b) gum arabic, and (d) a soluble soybean polysaccharide as the wall material. The solid
curves were drawn based on the Weibull equation.
Conclusion
Acyl ascorbate is synthesized through lipase-catalyzed-condensation of ascorbic acid
with fatty acid. Enzymatic synthesis of acyl ascorbate would be more advantageous than a
chemical method due to the simplicity of its reaction process and its high regioselectivity.
Further, it would be edible, because each substrate is eaten daily as a food component. Acyl
ascorbate might be hydrolyzed in digestion or on intestinal membrane by lipase, and then be
absorbed. Each substrate would separately function as an essential nutrient
in vivo
. Thus, it is
very useful that the oxidative stability of polyunsaturated fatty acid, which has various
physiological functions, is improved by esterification with ascorbic acid. Moreover, acyl
ascorbate would be used as an emulsifier. The emulsifier property changes by altering acyl
chain length. The application of acyl ascorbate for microencapsulation of a lipid as
antioxidative emulsifier would be a useful technology for suppressing or retarding the
oxidation of polyunsaturated fatty acid.
