Antimicrobial Properties of Chestnut Shell Extract as an Ecofriendly Approach for Food Preservation

Abstract

The chestnut industry generates large quantities of by-products, including the chestnut shell, which is a source of phenolic compounds. In this study, the MIC (minimum inhibitory concentration) of chestnut shell extract was determined using the disk diffusion method. The chestnut shell was freeze-dried and milled. The extract was obtained using an ultrasound-assisted technique using water 70%: ethanol 30% (v/v) and subsequently lyophilized. Muller–Hinton plates were inoculated with ~105 CFU/mL of microorganisms. Sterile paper discs (6 mm) were placed on the inoculated culture medium and impregnated with 10 µL of each extract. Seven concentrations of extract between 0.3% and 2.1% were tested. The plates were incubated for 24 h at 37 °C. The antibacterial efficacy of the extracts was indicated by a halo formed around the paper disk. This work was carried out in triplicate. Halos were found at 1.5%, 1.8%, and 2.1% on Listeria monocytogenes ATCC 7973 (8.32 ± 0.06 mm for 2.1%), Enterococcus faecalis 19433 (8.94 ± 0.41 mm for 2.1%), and Staphylococcus aureus ATCC (10.26 ± 0.19 mm at 2.1%). For the remaining microorganisms, no halos were observed. The tested extract showed antimicrobial activity, demonstrating its potential for the control of pathogens in the food industry.

Keywords

• chestnut shell
• antibacterial
• minimum inhibitory concentration
• antimicrobial activity
• pathogens
• <i>Enterococcus faecalis</i>