Assessing the use of acid-based sanitizers for enhancing the microbial safety and quality of collard greens and kale

The consumption of collard greens (CG) and kale (KA) and different formats of their products, e.g. juices, has increased significantly. However, there have been limited studies focusing on the enhancement of the microbial quality and safety of dark leafy green vegetables (DLGVs), especially large DLGVs, despite the occurrence of several outbreaks. The larger and more rough leaf surface is one major characteristically difference between CG/KA and other DLGVs (e.g. spinach). This study evaluated the antimicrobial effectiveness of acid-based washing (vinegar, lemon juice, and peracetic acid [PAA]) in controlling the populations of native microorganisms and artificially inoculated bacteria (Enterococcus faecium) on CG and KA during washing and storage. The washing procedure included a 5 min soaking (w/v ration 1:50) and a 15 s rinsing. Results showed that PAA (80 ppm, pH ∼ 4.00) ed to the greatest reductions in native fungi (∼1.2 and 1.4 log reductions) and bacteria (∼1.0 and 1.2 log reductions on CG and KA respectively) compared to 35 % vinegar (pH ∼2.75) and 13 % lemon juice wash (pH ∼2.83). PAA-washed CG and lemon juice-washed KA also exhibited the greatest additional reductions in fungal and bacterial populations during storage. E. faecium, used as a pathogen surrogate, had the largest reductions on CG and KA washed by PAA, ∼1.5 and 2.3 log reductions respectively. Lemon juice-washed CG and PAA-washed KA showed the greatest additional reductions in E. faecium during storage. Acid washing showed promising potential in protecting the microbial safety and quality of large DLGVs; the tested washing steps can be used at retail and home settings.