Comparative study on characteristics of mandarin peel extracts by biological processing.

Mandarin peel is a by-product from mandarin canning industry containing multiple functional substances with useful properties such as antibacterial and antioxidant activities. To evaluate the effect of bioprocessing, fresh mandarin peels were fermented by Rhizopus stolonifer JP13 for 4 days and then the peels' antioxidant and antimicrobial activities were tested. The flavonoiuds, hesperidin and VC contents in dry peels were also determined. The data showed that the fermented mandarin peels had promoted antibacterial activity against Escherichia coli, Staphylococcus aureus, Aspergillus flavus, and Candida albicans. An increased scavenging effect on free radicals, with 73.0% of·OH scavenging activities were obtained when compared with fresh mandarin peels. We also observed a significant increase on content of flavonoid (334%) and hesperindin (253.7%), a reduced scavenging effect on O2- free radicals (13.94%), and a decrease content of VC (13.7%). The presaging of mandarin peels by Rhizopus stolonifer JP13 strain will promote the functional activities of mandarin peels and accelerate the process of manufacture Citri Reticulatae Pericarpium.