Antimicrobial activity and antioxidant changes of spontaneously fermentedmangosteen (Garcinia mangostana L.) peel

Mangosteen peels have high total phenolic compounds that may be enhanced through fermentation. This research aimed to study the physical, microbial analyses and antimicrobial activity of spontaneously fermented mangosteen peel (SMP). Mangosteen peels, brown sugar and water were mixed at a ratio of 1:1:10 (mangosteen peel:sugar: water) and were spontaneously fermented for 4 weeks. By the end of fermentation, the pH gradually decreased from 4.31 to 3.75 and lactic acid bacteria were significantly higher than foodborne pathogens. However, the antioxidant properties of SMP decreased by Week 4. Therefore, unfermented mangosteen peel had better performance than SMP at Week 4 for the inhibition zone, minimum inhibitory concentration (MIC) and minimum bactericidal concentration (MBC) and killing time curve assay. With the exception to Clostridium perfringens and Vibrio parahaemolyticus, SMP had an inhibition zone of 10.67 to 12.67 mm for all bacteria with no significant difference between Week 0 and Week 4. The time-kill curve of SMP at higher concentrations killed Listeria monocytogenes and V. parahaemolyticus within 1 to 4 hrs. The results showed that the unfermented mangosteen peel had better antioxidant and antimicrobial properties and had the potential as an antimicrobial agent or preservative in food.