Sadhana Ravishankar, a UA associate professor in the School of Animal and Comparative Biomedical Sciences, received a $2.9 million grant from the U.S. Department of Agriculture’s National Institute of Food and Agriculture to help improve the safety and quality of farm-to-fork organic leafy greens through the use of natural sanitizers.
Ravishankar is testing plant extracts, essential oils and their active components for their bactericidal effects. Common household items like lemongrass, cinnamon, olives and oregano are among the ingredients that Ravishankar and her team are working with.
Post-harvest sanitation for leafy greens is an important step because these products are often consumed raw and hardly go through any heating process to kill the bacteria that may be present. The USDA estimates that 48 million illnesses and 3,000 deaths occur each year in the U.S. due to eating contaminated foods.
According to Ravishankar, the organic food industry is limited in the type and amount of chemicals they can use to sanitize their products. Currently, manufacturers are using peroxyacetic acid, hydrogen peroxide or low levels of chlorine for the sanitization process.
Spectral Instruments Imaging, a Tucson-based company, has provided the technology needed to capture the bactericidal effects of the natural sanitizers. By taking bioluminescent images, the researchers are able to see the reduction of bacteria like Salmonella enterica or E. coli on the leafy greens after treatment.
“I am excited about using the latest in imaging technology to understand this process,” said Govindaraj Dev Kumar, an animal and comparative biomedical sciences postdoctoral research associate working with Ravishankar.
Ravishankar explained that there are many benefits to using the natural sanitizers as opposed to chemical sanitizers. For example, it takes approximately three to five days after sanitization for the fresh produce to reach the consumer. Therefore, it is beneficial that the natural sanitizer continues to kill the bacteria during storage.
“The natural sanitizers are not only strong bactericidal agents, but they are also effective in storage,” Ravishankar said. “Chlorine and hydrogen peroxide only have a one-time killing effect on the microorganisms; you will not get any more increased reduction. But the plant compounds continue to act in storage, so they have residual activity. We are focusing on sampling not only immediately after treatment, but also at day one or day three, and so on.”
Because these are natural compounds, the essential oils and extracts are biodegradable as opposed to chlorine. Chlorine can react with organic matter and form potentially carcinogenic compounds like trihalomethanes.
Ravishankar found that the efficacy of natural sanitizers may not be affected by organic matter.
“If you have a dump tank filled with chlorine and you add your leafy greens, the efficacy goes down and you have to continuously add more chlorine,” Ravishankar explained. “But with the natural sanitizers, you can recycle the wash water. We did five different washes treating five to seven kilograms of leafy greens at a time. We have seen that even after five washes, these plant-based sanitizers are equally as effective, and no bacteria was found in the wash water.”
The plant-based compounds are also applicable in meat products. The USDA recommends heating the geometric cold center of ground meat to at least 71.1 degrees Celsius. However, the periphery of the meat can reach temperatures as high as 200 degrees Celsius and create carcinogenic compounds.
“When we add these plant-based compounds and then grill the meat, it will kill the E. coli bacteria found in meat, and thus you can reduce the temperature needed to kill the bacteria, which lowers the production of carcinogens,” Ravishankar said. Additionally, the natural sanitizers have health benefits due to their anti-oxidative activity and can reduce the occurrence of cancer, diabetes and high cholesterol.
The next step for Ravishankar and her team is to create a protocol for the sensory attributes that the plant extracts and essential oils have on the leafy greens. Within the next few months, she hopes to gather a panel of participants to smell and taste the leafy greens to see if they enjoy the flavor.
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