Passing state regulations for microbial contamination can be challenging. Excessive levels of mold, yeast, and bacteria can cause health problems for consumers. What happens when your flower doesn’t measure up to your state’s standards? You do have post-harvest treatment options that can save your buds. Microbial contamination can be remediated without damaging your final product.
Let’s take a closer look at the two main threats causing microbial contamination in post-harvest cannabis. The threats are environmental conditions during the harvest, drying, curing, and prepackaging storage; and the microenvironmental conditions of the packaged product across the supply chain from cultivator to consumer.
Microbial growth is enhanced or reduced by environmental conditions. Favorable conditions of temperature and relative humidity can cause microbes to grow and thrive after the plants have been harvested. It is obvious that microbial growth can occur in the large-scale environment of the grow, drying, curing, storage, transport, and retail shelf conditions. However, we must also consider the microenvironment of the cannabis in its final packaging for sale. The cannabis may also experience environmental conditions inside its packaging that promote additional microbial growth. As unusual as it sounds, this microenvironment must also be controlled to ensure that clean and safe cannabis is delivered to the consumer.
Once the cannabis has been packaged in sealed containers and sent to the dispensaries, additional tests for microbial contamination may show an increase in yeast and mold, even to the extent of causing a failure of the state-mandated requirements for microbial contamination. This recently happened in Colorado when state regulators inspected products from 25 dispensaries in Denver (2). There were unanticipated microbiological contamination failures of packaged product taken right from the shelves of these dispensaries: 20 of the 25 dispensaries had failed products. These products were not contaminated at the time of delivery from the supplier, as evidenced by METRC documentation. The origin of this contamination is likely because of conditions within the sealed packages that were favorable to microbial growth. When you consider the large-scale environmental conditions in which the cannabis is grown, harvested, dried, cured, and stored and compare it to the internal microenvironment of the packaging, it makes sense that similar environmental conditions would affect the packaged products in the same way. Just as we have seen that controlled environment agriculture (CEA) is necessary for successful indoor cultivation, we find that a form of CEA is necessary for the microenvironment inside the packaging of the harvested cannabis. You must consider both the large-scale and the microenvironments of the products across the entire supply chain from grower to consumer. Along with your best practices in cultivation, you must work as a team across the supply chain to ensure your products reach the consumer in the pristine state in which they left your grow facility. Plan to work closely with the various people or businesses that handle your product to ensure optimal environmental conditions that support clean cannabis. Mistakes made along the supply chain, by other people, can negatively affect microbial contamination test results, leading to the product being returned to you for reprocessing or destruction, and potentially leading to increased costs and possible questions about the cleanliness practices in your cultivation facility. In the worst case, not considering this source of “down the supply chain” microbial contamination may cause harm to sensitive consumers. Secondary to this is the loss to your profits and reputation that accompany a failure of this type.
Methods to Reduce Microbial Contamination in Post-Harvest Cannabis
Cannabis cultivators are the beneficiaries of decades of technology developments for consumer safety, including those developed for food safety across its supply chain (3). With cannabis in the mainstream of the consumer products, it is time to take advantage of those developments and use them to create safe cannabis that will always pass the state-mandated tests for microbial contamination. These methods are used to eliminate or greatly reduce the microbial contamination on the post-harvest cannabis and help to create the controlled microenvironment inside the cannabis packaging, necessary for ensuring safe cannabis across the supply chain.
The first step in the process is to kill the microbes in the post-harvest cannabis before it is packaged. The second step is to create the right microenvironment for the packaged cannabis. In sections below, we discuss two microbe-killing methods that will maximize your readiness to pass the state-mandated tests for cannabis post-harvest, before packaging. This is followed by a discussion of a method to ensure that you maintain the right microenvironment in the packaging. By following this two-step process, you will maintain your microbial cleanliness across the supply chain.
- K. McKernan, Y. Helbert, H. Ebling, A. Cox, L.T. Kane, and L. Zhang, “Microbiological examination of nonsterile Cannabis products” https://osf.io/vpxe5 (2018).
- T. Mitchell, Westworld, October 30, 2019 https://www.westword.com/marijuana/in-random-mold-tests-80-percent-of-denver-marijuana-dispensaries-fail-11467203.
- G.D. Molim, M. de Souza Braga, et. al., Curr. Pharm. Des. 22(27), 4264–4287(24) (2016).
- A.J. Brodowska and K. Smigielski, “Ozonation-an alternative decontamination method for raw plant materials” Food Sciences and Biotechnology http://www.bfs.p.lodz.pl (2013).
- B.P. Carter, Cannabis Science and Technology 2(4), 30–35 (2019).
- C. Hellerman, PBS News Hour, https://www.pbs.org/newshour/nation/scientists-say-governments-pot-farm-moldy-samples-no-guidelines.
- Y. Gargani, P. Bishop, and D.W. Denning, Mediterr. J. Hematol. Infect. Dis. 3(1), e2011005, https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3103256/ (2011).
- R. Kern, Cannabis Science and Technology 2(4), 16–29 (2019).
About the Coauthor
Dr. Jacklyn R. Green is a project manager, systems engineer, and scientist focused on today’s commercial cannabis enterprise. She is the cofounder and Chief Executive Officer of Agate Biosciences LLC, an agricultural consultancy. She earned her PhD at The University of Texas in astronomy, and subsequently applied her big-picture view and systems approach to problem solving at NASA’s Jet Propulsion Laboratory for more than 25 years. In her tenure there, she conducted detailed scientific research, managed complex projects and programs, and led teams of engineers and scientists to solve near impossible problems in a collaborative team setting. Now, she brings the best practices of management and systems engineering to cannabis businesses enhancing their financial and technical success in today’s stringent government-regulated environment.
About the Columnist
Dr. Roger Kern is a scientist and technologist who cares deeply about the cultivation and health of plants in the cannabis industry. With his PhD in microbiology from the University of California, Davis, Plant Growth Laboratory, he solves the most challenging problems in hydroponics, from studying the root microbiome to developing nutrients and lighting systems to ensure plant health and a disease-free lifecycle. He spent 22 years at NASA’s Jet Propulsion Laboratory as a scientist, technologist, and research leader before becoming the President of Agate Biosciences, a consulting firm for project management, systems engineering, and science in CEA for the past eight years. He leads developments to optimize sustainability, consistency, quality, and yield without compromising plant health. Direct correspondence to: [email protected]
How to Cite this Article
R. Kern and J.R. Green, Cannabis Science and Technology 2(6), 15-19 (2019).