**4. Conclusions**

*Biochemistry and Health Benefits of Fatty Acids*

algae oil (PAO) at 1:1 ratio (**Figure 3**).

tocopherol regeneration [18].

is expected to accelerate the degradation of lipid hydroperoxides as well as the degradation of the secondary oxidation products into shorter chain volatiles. The results of **Figure 3** showed that the goat milk emulsions containing a mixture (1:1) of the chromatographically purified algae oil (PAO) and the chromatographically purified *Hibiscus mutabilis* seed oil (PHMO) were more oxidized than the goat milk emulsions containing a mixture (1:1) of the chromatographically purified algae oil (PAO) and the natural *Hibiscus mutabilis* seed oil (NHMO). The protective effect of the natural *Hibiscus mutabilis* seed oil (NHMO) may be partially ascribed to the high content of tocopherols, especially γ-tocopherol. As pointed out earlier, the tocopherols are free-radical terminators, which donate a hydrogen to the peroxyl radical [12]. Goat milk contains citric acid [34], and citric acid is recognized as a metal chelator. The chelating properties of citric acid have been proposed to protect tocopherols during oxidation [35]. Therefore, citric acid in goat milk could enhance the antioxidant activity of tocopherols in the emulsions containing the natural *Hibiscus mutabilis* seed oil (NHMO) and the chromatographically purified

Ascorbyl palmitate (LAAP), which was added (200 μg/g of oil) to the natural *Hibiscus mutabilis* seed oil (NHMO) and the chromatographically purified algae oil (PAO) at 1:1 ratio, significantly reduced (p < 0.05) the extent of oxidation in this goat milk emulsion at 7-day and 14-day storage at 2°C (**Figure 3**). This protective effect of added ascorbyl palmitate (LAAP) was not observed in goat milk emulsions containing the chromatographically purified *Hibiscus mutabilis* seed oil (PHMO) and the chromatographically purified algae oil (PAO) at 1:1 ratio during 14-day storage at 2°C (data not shown). Ascorbyl palmitate (LAAP) had a more pronounced protective effect on the goat milk emulsion prepared with the chromatographically purified algae oil (PAO) and the natural *Hibiscus mutabilis* seed oil (NHMO) at 1:1 ratio by working synergistically with the γ-tocopherol isomer at 7-day and 14-day storage at 2°C (**Figure 3**). It is likely that ascorbyl palmitate retarded oxidation during storage of oil-in-water emulsions by direct scavenging of free radicals and

*p-Anisidine values of goat milk emulsions containing the different oils with and without added ascorbyl palmitate during 14-day storage at 2°C. Means (n = 3) within each storage day with different letters (a–c) are* 

**120**

**Figure 3.**

*significantly different (p < 0.05).*

This work showed the suitability of using *Hibiscus mutabilis* seed oil to protect marine-derived *n*-3 PUFAs in oil-in-water emulsions i.e., DHA-milk from oxidative degradation for 14 days at 2°C. The natural *Hibiscus mutabilis* seed oil efficiently protected the chromatographically purified algae oil from oxidation during emulsification and storage of DHA-enriched goat milk emulsion. The addition of ascorbyl palmitate to the natural *Hibiscus mutabilis* seed oil and the chromatographically purified algae oil prior to goat milk emulsification had a significant (p < 0.05) protective effect on DHA-enriched goat milk emulsion. The combination of differences in fatty acid composition and concentration of tocopherols for the natural *Hibiscus mutabilis* seed oil seems to affect the oxidative stability of the goat milk emulsions prepared with this oil. This study provides a useful precedent for understanding the antioxidant activity of *Hibiscus* seed oils in food and beverage emulsions containing marine *n*-3 PUFAs.

Complementary work is currently being performed in our laboratory to optimize the oxidative stability of DHA-enriched goat milk emulsions with added seed oils from *Hibiscus* species such as *Hibiscus moscheutos* and *Hibiscus dasycalyx* to be able to withstand the thermal and mechanical stresses of industrial processes.
