Polyphenolic antioxidants are mainly absorbed through passive paracellular permeation regulated by tight junctions. Some fatty acids are known to modulate tight junctions. Fatty acids resulting from the digestion of edible oils may improve the absorption of polyphenolic antioxidants. Therefore, we explored the effect of three edible oils on the intestinal absorption of caffeic acid. Rats were fed with soybean oil and caffeic acid dissolved in distilled water. Caffeic acid contents in the plasma collected up to 1 hr were quantified. The experiment was repeated with coconut oil and olive oil. Component fatty acids of the oils were individually tested in vitro for their effect on permeability of caffeic acid using Caco-2 cell monolayers. Highest absorption of caffeic acid was observed in animals fed with coconut oil. In vitro transport percentages of caffeic acid in 2.5 mmol/L solutions of fatty acids were 22.01±0.12 (lauric), 15.30 ± 0.25 (myristic acid), 13.59 ± 0.35 (linoleic acid), 3.70 ± 0.09 (oleic acid) and 0.10–2.0 (all other fatty acids). Lauric acid and myristic acid are the two major fatty acids present in coconut oil. Therefore, these fatty acids may contribute to the higher absorption of caffeic acid in the presence of coconut oil.

Limitations of natural antioxidants include relatively low antioxidant activity, narrow range of food systems where the antioxidants are effective and limited thermal stability compared to synthetic antioxidants. In the present study, the phenolic extract of coconut oil cake (COCE) was tested for antioxidant activity-related food stabilization. Heat stabilities of COCE and synthetic antioxidants were determined by measuring the induction time of sunflower oil enriched with heat-treated antioxidants. In the β-carotene-linoleate emulsion used for testing antioxidant activity, COCE can retain 96 ± 2% of initial colour intensity while BHT can retain 89 ± 2% of initial colour intensity at 60 µg mL -1 concentration after two hours. TBARS contents (MDA equivalents / kg of meat) in COCE-treated and control pork samples after 14 days was 2.80 ± 0.57 and 22.55 ± 2.30 respectively. Heat stability varies in the order butylated hydroxytoluene (BHT) < (butylated hydroxyanisole (BHA) < COCE < tertiary butylhydroxyquinone (TBHQ). The results of these experiments suggest that COCE is a versatile and thermally stable natural antioxidant mixture effective in stabilizing many food systems.Keywords: coconut oil cake; antioxidants; polyphenols; DPPH; food model systems.Practical Application: Ethanolic extracts of coconut oil cake can improve the shelf life of food emulsions, meat and polyunsaturated oils. Phenolic antioxidants responsible for these food stabilizing effects are highly thermally stable. Therefore, the extracts of coconut cake can be developed as commercial natural antioxidant preparations with potential applications in food industry.

Coconut milk is the aqueous extract of grated coconut kernel. In traditional cooking in the South Asian region, grated coconut kernel is hand-pressed with water to obtain a viscous white coconut milk known as first extract (FE). The coconut kernel remaining after the first extraction is further extracted with a fresh portion of water to obtain second extract (SE), which is less viscous. In the present study, the nutritional composition and the effect of FE and SE on the serum lipid profiles was evaluated. The results indicate that the lipid and protein contents of SE is equivalent to a 3 fold diluted solution of FE. However, the levels of sugars and phenolic contents of the SE cannot be achieved by the same fold ofdilution of FE. There is no significant difference (p < 0.05)in the lipid profiles of the rats fed with SE after 21 days.