Chemistry

How Drying and Curing Methods Can Make or Break Your Harvest

Anders Peterson
Written by Anders Peterson

By Anders Peterson, InSpire Transpiration Solutions

Too many cultivators spend precious time and energy tending to their plants for months at a time, only to sacrifice quality, quantity, and consistency during the drying and/or curing stages. Your harvest quality is optimal at the end of the flowering cycle, and it is up to you to maintain that level of quality throughout the postharvest process. Consider a winemaker – their job is to maintain the quality of the grapes from the vineyard and do them justice in the finished product. You won’t increase quality during drying or curing, but there are several methods you can implement to maintain quality and influence your final product.

 

Quantify data to increase consistency

The days of using anecdotal data and basing processes on guesstimates are over. To truly dial in the postharvest process, cultivators need to quantify data in the dry and cure rooms to produce consistently high-quality product in an increasingly competitive market.

  • Establish key performance indicators (KPIs) and metrics for postharvest processes: Consider measuring factors like number of plant touches, moisture removal rates per day, water activity, moisture content, and secondary metabolite content.
  • Determine your goals: The total time you allot for the drying/curing process will determine many of these metrics. Maybe your plant process flow, harvest schedule, or market demands means you only have seven days to dry a harvest, or maybe you have two or three weeks. What are your constraints and what are your goals?

 

Equip yourself with the right tools

The size of your postharvest rooms will depend on various factors like your plant support system and the height of your ceilings – unfortunately, there is no one-size-fits-all approach. Consider the anticipated weight of your harvest, your plant support/hanging style, spacing, height limitations, and your harvest schedule when sizing your dry room.

To ensure a successful dry/cure process, have the right tools on hand to help you retain proper moisture levels while maximizing terpenes and potency.

  • Light, high temperature, and time are the enemies of cannabis once harvested. Degradation due to ultraviolet light exposure, high temperatures, and waiting extended periods of time to complete the process can all lead to the decarboxylation of acidic cannabinoids, and eventually further degradation of cannabinoids into cannabinol (CBN), impacting the potency and chemotype of your final product. You may also experience a loss of terpenes and overall oxidation of the product. Aim for a well-sealed, positively pressurized room with just enough light to work safely.
  • A right-sized heating, ventilation, air conditioning, and dehumidification (HVACD) system will ensure precise moisture removal rates which is especially critical during the first 48-72 hours post-harvest to prevent mold and pathogen growth. The drying of cannabis is all about the precise removal of moisture, and if you do not have control of this process, the product quality will be sacrificed.
  • A consistent airflow pattern across the plants allows for effective and consistent moisture removal rates. Inconsistent airflow will over dry certain areas of the room and under dry others.
  • You’ll need a moisture content meter and a water activity meter; these data points are critical to the optimization of your process. There are dual water activity and moisture content meters available that greatly speed up the process of collecting this data and won’t destroy the product in the process.

 

Single harvest strategy or continual load-in strategy?

There are two dominant styles of operating dry and cure rooms with today’s cultivators: a single harvest batch load-in strategy, or a continual load-in strategy.

  • Single harvest strategy: This strategy involves one harvest going into its own dry or cure space with no other harvest batches or stages of drying/curing, allowing for more precise control of moisture removal rates and moisture content. The single harvest strategy is typically preferred due to the level of control throughout the process.
  • Continual load-in strategy: This strategy entails harvest batches of various stages all occupying the same space at once. For example, one harvest might fill up a third of the dry/cure room, another harvest will come into the same room a few days later, and another harvest a few days after that. A continual load-in strategy is possible, but most cultivators who use this method must run constant temperature and relative humidity setpoints, limiting their ability for precision control of moisture removal and drying rates.

 

Just keep the door shut!

If you don’t absolutely need to go into your dry/cure room, then don’t. The more you open the door, the more light you let into the room and the more the relative humidity of the room will fluctuate. Keep the lights off in the room if no one is using the space, and consider installing a light switch with a timer that will shut the lights off after a certain amount of time.

 

Use water activity and moisture content to optimize product quality, shelf life, and safety

Water activity (Aw) is a measure of the available water in your plants that can be utilized for microbiological growth. Water activity can range from 0 to 1, and the sweet spot for cannabis flower safety and quality is 0.55-0.65 Aw. Water activity is crucial for the safety and stability of your final products to ensure mold growth does not occur during storage and transportation. Water activity also contributes to product quality attributes associated with shelf life. Water activity testing is mandated in many states to ensure product safety for consumers.

Moisture content is also a regulated metric in many states, and typically, dry flower has to be below 15% moisture to pass safety testing. Moisture content is a big variable as cannabinoids are measured as a percentage of your product’s total weight. As moisture content increases, so will the sellable weight of your product, but potency will decrease. As the moisture content of your flower decreases, the potency on a lab report goes up. This balance between sellable weight and product potency is determined in the dry/cure room which is why it is so important to develop a system that provides precise control.

Drying and curing are complex, intertwined processes that are often overlooked, misunderstood, or mismanaged by entrepreneurs and cultivators alike. Drying is part of the curing story, but it’s not the whole story – drying is about removing enough moisture for the product to be smoked or processed, and curing is a controlled process that protects secondary metabolites and brings out the subtle nuances of each cultivar. Controlling the curing process creates predictable results and consistent product flow. An appropriate drying and curing strategy will increase price per pound and extraction yields, reduce product loss, increase shelf life and product quality – all of which will have a significant financial impact on your business.

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Anders Peterson

Anders Peterson

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