Vinegar as a Sanitizing Agent for Leafy Greens on Small Farms

Introduction: Small farms (revenue < $50,000/month) are not subject to USDA regulations regarding post-harvest practices and therefore have no set standards on washing produce. Fresh produce has been implicated in multiple foodborne illness outbreaks over the past decade. The use of effective sanitizers for washing produce may help reduce microbial contamination and increase shelf life.

Purpose: The objective of this research was to examine the sanitizing effects of white distilled vinegar solutions to improve the quality and shelf-life of leafy greens by enumerating aerobic microorganisms, coliforms, Escherichia coli, yeast, and mold.

Methods: To determine the efficacy of vinegar as a sanitizing agent we obtained mixed greens and romaine lettuce samples from local farmers. Vinegar solution (1.25% and 2.5% acetic acid) was prepared in a salad spinning device for home use. The lettuce was submerged for 30 sec, spun for 45 sec and allowed to air dry for 1 min. Each sample was stomached with sterile 0.1% peptone, diluted and plated on appropriate media. Aerobic Plate Counts (APC), E. coli/coliforms, and yeast and mold were evaluated for the samples. The microbial counts on the lettuce were evaluated pre- and post-intervention.

Results: The vinegar solutions of 1.25% and 2.5% acetic acid reduced APCs on mixed greens by ~1 log CFU/g and on romaine by ~2 log CFU/g. The E. coli and coliforms counts were reduced on mixed greens and romaine by ~0.5 log CFU/g and ~1.75 log CFU/g, respectively. The intervention reduced yeast and mold counts by ~2 log CFU/g and ~1.5 log CFU/g on both mixed and romaine lettuce samples, respectively.

Significance: These results demonstrate that vinegar can reduce microbial contamination and possibly improve the shelf-life of leafy greens. Furthermore, this can help small farmers who may not have the means to use industrial washers to sanitize fresh produce.