Incresing antioxidant activity and reducing decay of blueberries by essential oils

Authors: Wang, Chien; Wang, Shiow; CHEN, CHITSUN - COA-HDARES, TAIWAN

Submitted to: Journal of Agriculture and Food Chemistry
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 3/4/2008
Publication Date: 5/28/2008
Citation: Wang, C.Y., Wang, S.Y., Chen, C. 2008. Incresing antioxidant activity and reducing decay of blueberries by essential oils. Journal of Agriculture and Food Chemistry. 56:3587-3592.

Interpretive Summary: Little information is available concerning changes of antioxidant levels in fresh fruits and vegetables after harvest or how to maintain or increase these values. This is important because antioxidants are known to be beneficial to our health, but their levels can decline rapidly after harvest due to mishandling. In our study, we treated blueberry fruit with natural essential oils (compounds extracted from plants) immediately after harvest and found that this treatment helped maintain levels of antioxidants as well as reduce decay and lengthen storage life of blueberries. Therefore, it is possible that both health benefits and shelf-life of berry fruit can be improved by postharvest treatment with essential oils. This information can be useful to other scientists, berry industry, and beneficial to consumers.

Technical Abstract: Several naturally occurring essential oils including carvacrol, anethole, cinnamaldehyde, cinnamic acid, perillaldehyde, linalool, and p-cymene were evaluated for their effectiveness in reducing decay and increasing antioxidant levels and activities in ‘Duke’ blueberries (Vaccinium corymbosum). Carvacrol, anethole, and perillaldehyde showed the capability to promote total anthocyanins and total phenolics and enhance antioxidant activity in fruit tissues expressed as oxygen radical absorbance capacity (ORAC) and hydroxyl radical (·OH) scavenging capacity. All essential oils tested in this study showed some degree of inhibition of fruit decay development as compared to the control. The most effective compound in terms of mold retardation was p-cymene, followed by linalool, carvacrol, anethole, and perillaldehyde. Cinnamic acid and cinnamaldehyde also suppressed mold growth, but to a lesser extent. Treatment with carvacrol, anethol, or perillaldehyde also significantly increased the levels of fructose, glucose, and citric acid. Individual flavonoids were variably affected by the essential oils. The levels of chlorogenic acid, which was the major phenolic compound in blueberry fruit, were enhanced by all essential oils in this study. Increased amounts of quercetin 3-galactoside and quercetin 3-arabinoside were also found in all treated fruit except samples treated with linalool or p-cymene. The major anthocyanin, malvidin 3-galactoside, was enhanced by all essential oils tested except linalool and p-cymene. The levels of other individual anthocyanins including petunidin 3-galactoside, delphinidin 3-galactoside, petunidin 3-glucoside, petunidin 3-arabinoside, delphinidin 3-arabinoside, and cyaniding 3-galactoside were higher in the treated fruit than in the control. Those essential oils that have positive effects on enhancing anthocyanins, phenolic compounds and antioxidant activity of fruit, but negative effects on microbial growth and decay development warrant further evaluation.