Abstract
Peanut skin extract (PSE) and grape seed extract (GSE) are derived from waste products in the wine and peanut industries, respectively. Both have high concentrations of polyphenols, known to possess antioxidant and antimicrobial properties. PSE primarily contains “A‐type” procyanidins, while GSE primarily contains “B‐type” procyanidins. These differ structurally, but are both isomers of epicatechin dimers. The objective of this study was to evaluate the antimicrobial effects of PSE containing A‐type procyanidins and GSE containing B‐type procyanidins against select foodborne pathogens (Listeria monocytogenes, Escherichia coli O157:H7, and Salmonella Typhimurium). The minimum inhibitory concentration (MIC) of the two extracts on L. monocytogenes, E. coli O157:H7, and S. Typhimurium was determined using the pour plate method. GSE had a significantly lower MIC (p ≤ .05) than PSE for L. monocytogenes (GSE = 60.6 ppm, PSE > 68.2 ppm) and S. Typhimurium (GSE = 45.7 ppm, PSE = 60.6 ppm), but no difference in inhibition of E. coli O157:H7. Since GSE contributed to greater inhibition, GSE extract was fractionated into monomer‐rich (consisting primarily of catechins, epicatechins, and epicatechin gallates) and oligomer‐rich (consisting of dimers, trimers, tetramers, up to decamers) components. Growth curves of all three pathogens in the presence of full extract, monomer and oligomer fractions were compared separately. None of the extracts inhibited S. Typhimurium growth. Generally, the extract containing greater oligomer components inhibited growth of L. monocytogenes and E. coli O157:H7 when compared to the control. Results indicate that an extract with type B procyanidins higher in oligomers may have greater antimicrobial properties.
Highlights
In recent years, the demand for the use of natural ingredients has placed an emphasis on identifying natural food preservatives
The objective of this study was to evaluate the antimicrobial effects of peanut skin extract (PSE) containing A-type procyanidins and grape seed extract (GSE) containing B-type procyanidins against select foodborne pathogens
Vitaflavan is a water-soluble extract of Vitis vinifera seeds, and manufacturer specifications indicate that it contains 24% w/w monomeric procyanidins, 42% w/w dimeric/ trimeric procyanidins, and 10% w/w larger procyanidins
Summary
The demand for the use of natural ingredients has placed an emphasis on identifying natural food preservatives. One of the benefits of examining these two products is that they are derived from waste products by the industries that produce grape juice/wine and shelled peanuts, respectively (Shi, Yu, Pohorly, & Kakuda, 2003; Yu, Ahmedna, & Goktepe, 2005, 2010) Identifying value in these products could result in less waste, complete utilization of raw products, and provide an all-natural alternative to synthetic preservatives. Identifying which component of the procyanidin-rich polyphenol is most effective may inform researchers on the factor that contributes the most to antimicrobial properties. This may help with the selection of other natural extracts using their compound profiles to determine which ones will have the best potential
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