Natural antimicrobials for Listeria? Yes, we (Pe)can
Roasted pecan shell powder (PSP) extracts were more effective than unroasted pecans shell extracts and extracts of both types appeared to prevent attachment of Listeria to the chicken skin model
The solvent free extracts of pecan shells inhibited Listeria strains at minimum inhibitory concentrations (MICs) as low as 0.38%, said Babu et al.
The use of synthetic chemicals and chemical preservatives is restricted for use in certified organic processing plants in the US, the microbial safety of organic foods may be increased by use of natural antimicrobials that can meet the requirements of USDA standards.
Pecan shells antimicrobial properties
Researchers examined the antimicrobial properties of pecan shell and shell powder extracts prepared using proprietary solvent free extraction system against the growth of L. monocytogenes serotypes.
They also studied the effect of the extracts on natural microflora of poultry skin, and the effects on L. monocytogenes and Listeria spp. attached to chicken skin.
Unroasted and roasted organic pecan shells were subjected to solvent free extraction to produce antimicrobials that were tested against Listeria spp. and L. monocytogenes serotypes to determine minimum inhibitory concentrations (MIC) of antimicrobials.
The effectiveness of pecan shell extracts were tested using a poultry skin model system and the growth inhibition of the Listeria cells adhered onto the skin model were quantified.
Antimicrobial effectiveness tests on a poultry skin model exhibited nearly a 2 log reduction of the inoculated cocktail mix of Listeria strains when extracts of pecan shell powder were used.
The extracts produced greater than a 4 log reduction of the indigenous spoilage bacteria on the chicken skin.
Sensitivity difference in strains
With the exception of strain Lm190 on unroasted shell extract and Lm191 on roasted shell extract, all strains and their cocktail mixes exhibited significant sensitivity to both extracts.
Unroasted and roasted pecan shell extracts were tested for antimicrobial effectiveness at concentrations ranging from 0.375% to 48%.
Chicken skin samples were collected by peeling from fresh chicken drumsticks purchased at a grocery store a few hours prior to each experiment.
“The reason for lower % MIC for roasted PSP extract could also be due to a higher concentration of the antimicrobial compounds because of moisture loss during roasting leading to inherent differences in chemical composition of the smoke extracts,” said the researchers.
The bacterial strains used were seven Listeria species that included five L. monocytogenes (Lm) strains, one of L. innocua and L. ivanovii strains from the Center for Food Safety culture collection at the University of Arkansas.
Source: Journal of Food Science
Online ahead of print, DOI: 10.1111/1750-3841.12311
“Efficacy of Antimicrobials Extracted from Organic Pecan Shell for Inhibiting the Growth of Listeria spp.”
Authors: Dinesh Babu, Philip G. Crandall, Casey L. Johnson, Corliss A. O'Bryan, Steven C. Ricke
