Pecan Shell Extract Coating Fights Bacteria on Blueberries

Greg Howard
27th April, 2024

Pecan Shell Extract Coating Fights Bacteria on Blueberries

Image Source: Natural Science News, 2024

Key Findings

  • At Louisiana State University, pecan shell extracts were found to have antimicrobial properties
  • The extracts, when applied to blueberries, reduced harmful bacteria without affecting fruit quality
  • This natural method could improve food safety and shelf life, using what was once waste
In the quest to find sustainable ways to preserve food and enhance food safety, researchers at Louisiana State University Agricultural Center have turned their attention to a by-product often regarded as waste: pecan shells[1]. Pecan shells, typically discarded during nut processing, are not just agricultural refuse but a treasure trove of bioactive compounds with antimicrobial properties. These properties offer a natural solution for extending the shelf life of perishable foods and reducing foodborne illnesses. The recent study focused on the antimicrobial efficacy of pecan shell extract (PSE) both in the lab (in vitro) and on actual food products (in vivo). In the lab, researchers tested aqueous (A-PSE) and ethanol (E-PSE) pecan shell extracts incorporated into pullulan, a natural polysaccharide film, against various bacterial and fungal strains. The diameter of the area where microbial growth was inhibited around the discs was measured to determine effectiveness. The in vivo part of the study involved spraying a mixture of aqueous pecan shell extract and pullulan (PSE-P) on blueberries that were inoculated with common foodborne pathogens such as Listeria monocytogenes, Salmonella enterica, and Staphylococcus aureus, and then stored under refrigeration. The findings revealed that both A-PSE and E-PSE films were more effective against Gram-positive bacteria, with no antifungal effect at the concentrations tested. When applied to blueberries, PSE-P significantly reduced the levels of Listeria monocytogenes immediately after application and maintained this effect for up to five days compared to control or pullulan-only treatments. Interestingly, the PSE-P coating did not significantly impact the survival of S. enterica, S. aureus, or native fungal populations on the blueberries. Moreover, the PSE-P coating preserved the firmness and quality of the blueberries without affecting their color, total soluble solids (TSS), or pH during the 15-day storage period. It also reduced the spoilage rate and minimized weight loss, which are important factors in maintaining the marketability and consumer appeal of fresh produce. This study builds on previous research that highlighted the potential of pecan shells as a source of natural antimicrobials. Earlier studies found that pecan shells contain high concentrations of phenolic compounds, which are known for their antioxidant and antimicrobial properties[2][3]. These compounds, such as ellagic and gallic acids, have been identified in both pecan kernels and shells, with shells containing significantly higher concentrations[2]. The variability in phenolic content and antiradical activity was also noted to depend on the pecan variety and the method of extraction[3]. Additionally, the application of natural antimicrobials derived from pecan shells has been shown to be effective against Listeria spp. in meat processing, suggesting that pecan shell extracts could be a valuable asset in organic food production[4]. The use of pullulan coatings on fruits like blueberries has been demonstrated to extend shelf life by acting as a barrier that reduces respiration rate and controls microbial growth[5]. The integration of pecan shell extracts into pullulan coatings represents an innovative approach to food preservation that leverages the antimicrobial properties of natural compounds. It offers a dual benefit of utilizing a waste product and reducing reliance on synthetic preservatives, aligning with the growing consumer demand for natural and organic food products. As the food industry continues to seek out sustainable and effective methods to ensure food safety and quality, the findings from the Louisiana State University Agricultural Center suggest that pecan shell extracts could play a significant role. The potential of these extracts to serve as a natural antimicrobial coating for fresh produce like blueberries opens the door to further research and development. The prospect of reducing food waste while also improving food safety is a compelling one, and pecan shell extracts may soon be a key ingredient in the recipe for a more sustainable food system.



Main Study

1) Antimicrobial screening of pecan shell extract and efficacy of pecan shell extract-pullulan coating against Listeria monocytogenes, Salmonella enterica, and Staphylococcus aureus on blueberries.

Published 30th April, 2024 (future Journal edition)

Related Studies

2) Phenolic compounds and antioxidant activity of kernels and shells of Mexican pecan (Carya illinoinensis).

3) Antioxidant Properties of Pecan Shell Bioactive Components of Different Cultivars and Extraction Methods.

4) Efficacy of antimicrobials extracted from organic pecan shell for inhibiting the growth of Listeria spp.

5) Effect of Pullulan Coating on Postharvest Quality and Shelf-Life of Highbush Blueberry (Vaccinium corymbosum L.).

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