Mild alkaline hydrolysis is an efficient and low‐cost method for improving the free phenolic content and health benefit of pomegranate peel extract

Pomegranate peel is the main byproduct of pomegranate juice manufacture and is rich in phenolic acids, but most of which exist in the bound form with low bioavailability. A simple, low‐cost procedure for releasing phenolic acids from pomegranate peel was developed, which uses a mild alkaline treatment of the peel at room temperature. Results showed that when the peel was treated with 0.5 mM NaOH for 3 h, the concentration of ellagic acid, one of the two main phenolic acids present, almost doubled, while gallic acid, the other main phenolic, which was not found in the free form, was released at a concentration almost twice as high as that of ellagic acid. With the release of the two phenolic acids, the extract of the pomegranate peel showed remarkable increases in their antioxidant activity measured by three different essays. However, more severe alkaline treatment either by extending the hydrolysis time to 6 h or longer, or by using a higher concentration of NaOH (2 mM), resulted in decreases in the phenolic acids, possibly as a result of alkaline‐induced degradation, with corresponding decreases in antioxidant activities. These results showed that the mild alkaline treatment process could be a low cost but efficient method that can be used to increase the level of phenolic acids and hence the potential value of pomegranate peel extract. PRACTICAL APPLICATIONS: Pomegranate peel is the main byproduct of pomegranate juice manufacture and is rich in phenolic acids, but most of which exist in the bound form with low bioavailability. A simple, low‐cost procedure for releasing phenolic acids from pomegranate peel was introduced in this article, which uses a mild alkaline treatment of the peel at room temperature. The method was practical and the extract could be used as antioxidant and active supplement.