Total Phenolics, Antioxidant and Antibacterial Activity of Commercial Pomegranate Based Juices from Greece

Abstract

Pomegranate (Punica granatum L.) is a fruit that increasingly is becoming recognised for its health properties, prompting the development of derivate products that attempt to keep the main properties of the raw fruit. Pomegranate can be consumed as a fruit or is used for the production of juices, jams, jellies, flavorings for drinks etc. Pomegranate juices may also be combined with other fruit juices. In the present study, five commercial pomegranate-based juices (natural pomegranate juice, natural pomegranate-strawberry juice and natural pomegranate-blackberry juice, pomegranate juice from concentrate and pomegranate-grape juice from concentrate) were analyzed for total phenolics, antioxidant and antibacterial activity. The amount of total phenolics was measured with the Folin-Ciocalteu reagent and the antioxidant capacity was determined by the scavenging activity against 2,2-diphenyl-1-picrylhydrazyl (DPPH). The antibacterial activity of the juices was screened using two Gram-positive bacteria (Staphylococcus aureus, Listeria monocytogenes) and one Gram-negative (Escherichia coli). Results showed that the juices from concentrate contained noticeably higher total phenolics than the other juices. Furthermore, the addition of other fruit juices (blackberry, strawberry) to the natural pomegranate juice increased the amount of the phenolics. The DPPH method revealed that higher concentration of phenolic content of the juices is associated with higher radical scavenging activity. In the microbiological assay, the most sensitive bacteria to the juices tested were S. aureus and E. coli. Little or no inhibitory effect was observed against L. monocytogenes.