Researchers investigated the effects of peanut white kernel and peanut skin on three foodborne enteric bacterial pathogens.
The antimicrobial and prebiotic-like effects of both parts of peanuts on growth of probiotic Lactobacillus and on EHEC, S. Typhimurium, and L. monocytogenes were studied.
They found that within 72 hours, peanut flour inhibited growth of EHEC, while peanut skin extract inhibited Listeria monocytogenes but promoted the growth of EHEC and Salmonella Typhimurium.
The cell adhesion and invasion abilities of the three pathogens to the host cells were also reduced by 0.5% peanut flour and 0.5% peanut skin extract.
Combined effects of peanut flour and probiotics
The study showed the prebiotic-like effect of peanut flour and inhibitory effect of peanut skin extract on Lactobacillus.
Combining L.casei and peanut flour showed a drastically inhibitory effect against the three foodborne bacterial pathogens.
“Two possible explanations for this might be that compounds in peanut flour either induced the number of L. casei or the antimicrobial metabolites production by L. casei, both of which contribute to the competitive exclusion of foodborne pathogens,” said the researchers.
Researchers looked at combining probiotics and prebiotics in inhibiting foodborne pathogens.
Use of L. casei and peanut skin extract only showed strong inhibition on growth of L. monocytogenes.
“The antimicrobial effect of peanut skin extract itself on L. monocytogenes might be one explanation of this, as a result of which, though the amount as well as the inhibitive effect of L. casei in the mixed culture were attenuated by peanut skin extract, L. monocytogenes still was not able to survive in the supplemented mixed culture.”
Inhibiting growth
Growth of the Gram-negative foodborne pathogen EHEC was inhibited by nearly 1 log CFU/mL within 48 hours of incubation in the presence of peanut flour.
The Gram-positive foodborne pathogen L. monocytogenes was inhibited by more than 1 log CFU/mL at 24 hours by use of peanut skin extract.
In the same study, it was found that L. casei, peanut flour, and peanut skin extract can reduce foodborne pathogens colonization on human intestinal cells.
“In order to attach and colonize host's gut, foodborne pathogens have to compete with normal gut microflora, as a consequence of which, we hypothesize that pretreatment of L. casei reduce the adhesive and invasive activities of pathogens by occupying the intestinal cell surface receptors.
“In addition, bioactive components in peanuts such as phenolic acids and flavonoids might inhibit the colonization of pathogens by reducing their flagellin and adhesin level.”
Increased activities of cell attachment by L. casei with peanut flour may explain why combined pretreatment could exhibit much stronger adhesion and invasion inhibitive effect on the pathogens.
Source: Journal of Food Science, published by the Institute of Food Technologists (IFT)
Online ahead of print, DOI: 10.1111/1750-3841.12785
“Functional Properties of Peanut Fractions on the Growth of Probiotics and Foodborne Bacterial Pathogens”
Authors: Mengfei Peng, Elizabeth Bitsko and Debabrata Biswas