Effects of various pressing programs and yields on the antioxidant activity, antimicrobial activity, phenolic content and colour of pomegranate juices.

Pomegranate juice (PJ) samples were produced with three different pressing programs: (1) 1.2-4.8 bar for 25 min, (2) 1.2-2.4 bar for 15 min and (3) 1.2-1.8 bar for 5.5 min. Respective juice yields were 39.2%, 33.2% and 27.2%. Effects of pressing pressure-time and yield on total phenolic (TP) content, condensed tannin (CT) content, monomeric anthocyanin (MA) content, antioxidant activity (AOA) and antimicrobial activity (AMA) of the samples were determined. Strong positive linear correlations were found between the pressing pressure with AOA (r=0.973) and TP content (r=0.979), while negative logarithmic correlations were found between pressing pressure with the contents of CT (r=-0.778) and MA (r=-0.955). Among 12 microorganisms tested, Bacillus megaterium, Bacillus subtilis, Staphyloccocus aureus and Pseudomonas sp. were found to be sensitive to juice samples. However, increasing pressing pressure and yield did not lead to a significant change on the AMAs of the juices.