Bio-based phenolic branched-chain fatty acid emulsion achieved similar reductions of Listeria innocua population on apple fruit as chlorinated water

Authors: Ryu, Victor; CHUESIANG, PIYANAN - Chulalongkorn University; Uknalis, Joseph; Ngo, Helen; Jin, Zhonglin; Fan, Xuetong

Submitted to: Food Control
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 1/16/2024
Publication Date: 1/17/2024
Citation: Ryu, V.N., Chuesiang, P., Uknalis, J., Lew, H.N., Jin, Z.T., Fan, X. 2024. Bio-based phenolic branched-chain fatty acid emulsion achieved similar reductions of Listeria innocua population on apple fruit as chlorinated water. Food Control. 10(3):e24901. https://doi.org/10.1016/j.heliyon.2024.e24901.
DOI: https://doi.org/10.1016/j.heliyon.2024.e24901

Interpretive Summary: Chlorine is a commonly used sanitizer by the produce industry. However, use of chlorine has two drawbacks: the formation of potentially harmful byproducts, and difficulty maintaining effective levels due to its reactivity with organic materials in the water. Therefore, alternative sanitizers, preferably from natural and renewable sources, are needed. This study was conducted to evaluate the efficacy of our patented bio-based antimicrobials produced from phenolic compounds and fatty acids in inactivating Listeria and maintaining the quality of apples. Apple fruits were washed with an emulsion of the novel phenolic fatty acids and with chlorine as a comparison. Results showed that the emulsion at 500 part per million had similar antimicrobial efficacy as chlorine, achieving up to 99.9% reductions of Listeria populations on apple fruits. In addition, its efficacy is less affected by the presence of organic materials compared to chlorine. Furthermore, the treatment did not significantly affect the quality of apples during 2-weeks of shelf life. Therefore, the compound can be used as a wash for apples to enhance microbial safety without affecting their quality. The study may be of value to the fruit industry seeking alternatives to chlorine.

Technical Abstract: This study evaluated whether PBC-FA emulsion could have similar antimicrobial activity as chlorine when used for washing apples. An ethanol-dissolved phenolic branched-chain fatty acid (PBC-FA) was mixed with water (pH 7) to create a PBC-FA emulsion. The resulting emulsion droplets were around 200 nm in size. The stability of the emulsion was tested by storing it at 4 and 20°C for 30 days. The antimicrobial activity of the PBC-FA emulsion was assessed against Escherichia coli (E. coli) and Listeria innocua (L. innocua) (8 log CFU/mL). It was found that the PBC-FA was effective against L. innocua, causing membrane permeation at a concentration of 14.1 µg/mL. However, it did not show the same effect on E. coli O157:H7 at the tested concentrations. The potential of using the PBC-FA emulsion as a wash against L. innocua on apples was also examined. Results demonstrated that a 500 µg/mL PBC-FA emulsion with 5% ethanol exhibited comparable antimicrobial activity (2-3 logs reductions) to a commonly used sanitizer, a 20 µg/mL chlorine solution. Moreover, the PBC-FA emulsion showed improved antimicrobial efficacy in the presence of organic matter compared to chlorine. The impact of PBC-FA on apple quality was evaluated by monitoring changes in color, firmness, and sugar content over a 14-day storage period at 20°C. The findings indicated that the quality of the apples remained unaffected by the PBC-FA emulsion, suggesting its suitability as an apple wash without compromising quality.