Effects of a novel combination of gallic acid, hydrogen peroxide and lactic acid on pathogen inactivation and shelf-life of baby spinach

Authors: Zhou, Bin; Luo, Yaguang - Sunny; Nou, Xiangwu; MWANGI, ESTHER - Agricultural Research Organization - Volcani Center; POVERENOV, ELENA - Agricultural Research Organization - Volcani Center; DEMOKRITOU, PHILIP - Harvard University; Fonseca, Jorge

Submitted to: Food Control
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 7/27/2022
Publication Date: 1/1/2023
Citation: Zhou, B., Luo, Y., Nou, X., Mwangi, E., Poverenov, E., Demokritou, P., Fonseca, J.M. 2023. Effects of a novel combination of gallic acid, hydrogen peroxide and lactic acid on pathogen inactivation and shelf-life of baby spinach. Food Control. 143. Article 109284. https://doi.org/10.1016/j.foodcont.2022.109284.
DOI: https://doi.org/10.1016/j.foodcont.2022.109284

Interpretive Summary: Baby spinach is nutrient-rich and in high demand by consumers owing to its convenience and freshness. However, it is also prone to contamination by spoilage microorganisms and foodborne pathogens during production under sub-optimal operation conditions, leading to compromised food quality and substantial food safety risks to consumers. In this study, ARS scientists collaborated with researchers in Israel and Harvard University in formulating and testing a novel antimicrobial solution for fresh produce. Using a combination of gallic acid, hydrogen peroxide, and lactic acid, the treatment solution significantly reduced the survival of artificially introduced pathogenic bacteria on spinach leaves while maintaining quality and shelf life of the treated produce. The results of this study indicated that such novel solution have potential for improving the quality and microbial safety of food products. This formulation can be an effective alternative to chlorine as sanitizer in produce cleaning operations especially for organic produce or where the application of chlorine is restricted.

Technical Abstract: Recurring human pathogen outbreaks associated with consumption of whole and fresh-cut leafy greens reaffirmed the challenge with microbial safety of produce consumed fresh. Here we report a novel combination of gallic acid, hydrogen peroxide, and lactic acid (GHL) on inactivation of foodborne human pathogens on spinach leaves. Baby spinach samples inoculated with Escherichia coli O157:H7 and Listeria monocytogenes were treated with the GHL formulation and compared with commonly used sanitizers including chlorine (50 mg/L) and peroxyacetic acid (80 mg/L). The inactivation, growth, survival or die-off of E. coli O157:H7 and L. monocytogenes along with quality and shelf life were determined immediately after treatments and during cold storage for up to 14 days. Washing baby spinach with GHL for 2 minutes reduced E. coli O157:H7 by 0.9 Log CFU/g while the washing with chlorine and peroxyacetic acid reduced E. coli O157:H7 by 0.6 Log CFU/g. E. coli O157:H7 population declined over time during cold storage in all treatments. However, GHL-treated samples remained with a significantly lower E. coli O157:H7 population throughout the storage period. On the other hand, all treatments showed significantly higher reduction of L. monocytogenes populations than the control produced with the water wash, while no significant difference was observed among GHL, chlorine, and peroxyacetic acid treatments. L. monocytogenes grew during storage and the difference among all treatments was not significant. GHL washed samples showed slight browning on rib edges and injured leaf surfaces, which disappeared within three days during storage. No other significant quality difference was observed among treatments. The results suggest that GHL can serve as alternative to conventional sanitizers for fresh produce washing. It could be especially useful for the organic produce industry or where the application of chlorine is prohibited.