Abstract

Background: Peanuts are crucial leguminous crops with global recognition in agricultural, dietary, and medicinal importance. The continuous attention drawn to antimicrobial resistance, and post-harvest losses raises research interests to explore natural alternatives to combat antimicrobial resistance and promote preservation of foods for longer shelf life. For these reasons, we evaluated the antimicrobial and preservative characteristics of three varieties of peanut peel extracts (PPEs). Methods: 0.5 grams of the PPEs were each soaked in 50 ml of sterile distilled water for 24, 48 and 72 hours. Five concentrations (0.8, 0.85, 0.9, 0.95 and 1%) of the extracts were reacted with E. coli, S. aureus, S. typhi and K. pneumoniae, by ascertaining the zones of inhibition, minimum inhibitory and minimum bactericidal concentrations. Also fruits (orange, banana, grape and apple) and vegetables (scotch bonnet pepper, tomato, onion and carrot) were subjected to the extracts for seven days for shelf-life assessment. Results: The Spanish variety, at the concentration of 1%, inhibited K. pneumoniae with a zone of 0.33±0.06 cm, followed by S. typhi (0.27±0.08 cm), S. aureus (0.15±0.17 cm), and E. coli (0.08±0.06 cm). The 0.8% showed no inhibition of E. coli and S. typhi. The Valencia variety showed the highest inhibition for K. pneumoniae at 1% (0.52±0.06 cm). Interestingly, its 0.8% concentration recorded a zone of 0.25±0.09 cm against E. coli. Moreover, the Virginia variety inhibited K. pneumoniae at 1% (0.53±0.08 cm) and against S. aureus at 0.95% (0.33±0.03 cm), while S. typhi was modestly inhibited at 0.95% (0.53±0.03 cm). There was no significant difference between the concentrations i.e. p>0.05 Furthermore, apple and onion were the most preserved and banana, the least preserved by the Spanish variety. This trend was observed in all the varieties and concentrations, with no significant difference between them (p>0.05). Conclusion: The three PPEs exhibited both antimicrobial and preservative characteristics at varying degrees of efficacy especially with the 72 hours soak duration and can therefore be employed against microbial resistance, and as natural preservatives for fruits and vegetables.

Keywords

Spanish, Valencia, Virginia cultivar, E. coli, S. aureus, K. pneumonia, S. typhi, antimicrobial, preservative, susceptibility