Impact of Water Activity on the Chemical Composition and Smoking Quality of Cannabis Flower: The Science of Smokability Phase I Results

authors: Allison Justice, Riley Kirk, Ashley Manning, Markus Roggen, Miyabe Shields

This study represents one of the first to investigate both the subjective quality of cannabis smoking, as reported by consumers, and objective measurements through chemical analysis. The research focuses on the role of water activity (aW) in cannabis drying and curing, and its effect on cannabinoid and terpene delivery, consumer experience, and the chemical composition of cannabis smoke.

Key Findings

• Terpene Yield: The study found that higher water activity (0.65 aW) consistently delivered higher terpene concentrations, contributing to a better aroma and flavor during smoking. Terpenes play a significant role in the sensory experience and may modulate the psychoactive effects of cannabis.

  
  

• Cannabinoid Yield: Despite variations in water activity, cannabinoid yields (specifically THC and CBG) were similar across the tested moisture levels, suggesting water activity has little impact on cannabinoid yield. However, pre-rolls at 0.85 aW, which were unsafe for consumption due to microbial growth, had substantially lower concentrations of both cannabinoids and terpenes, highlighting the importance of maintaining safe moisture levels.

  
  

• Irritation and Ash Color: Consumers reported that lower water activity (0.45 aW) led to more irritating smoking experiences, while higher water activity (0.65 aW) was perceived as less irritating. Additionally, the ash color was consistently lighter at higher water activity, which is often associated with better quality cannabis. The color difference was statistically significant, further supporting the sensory difference between the two moisture levels.

  
  

• Elemental Composition: Cannabis ash showed high levels of sulfur and phosphorus, which could have implications for consumer health and product quality, suggesting the need for further research on these elements.

  
  

• Financial Impact: The moisture content of cannabis (related to water activity) can significantly affect the weight and market value of the product. At 0.45 aW (5% MC), the flower loses about 18.14 grams per pound compared to the 0.65 aW (9% MC), which could lead to a revenue loss of $27.20 per pound for cultivators, highlighting the need for careful water activity management.

Key Highlights from the Study

• Water Activity and Terpene Delivery: Higher water activity (0.65 aW) enhances terpene yield, improving the aroma and flavor during smoking.

  
  

• Cannabinoid Yield: Water activity did not significantly affect cannabinoid yield (THC, CBG), but pre-rolls at 0.85 aW showed lower cannabinoid and terpene levels due to microbial risks.

  
  

• Consumer Experience: Pre-rolls with 0.45 aW were more irritating to smoke, and lighter ash at 0.65 aW was linked with a better quality smoking experience.

  
  

• Elemental Composition in Ash: Elevated sulfur and phosphorus levels in cannabis ash suggest the need for further investigation into the implications for consumer health and product quality.

  
  

• Economic Impact: The difference in water activity (5% vs. 9% MC) corresponds to an 18.14 grams per pound weight loss, leading to potential financial losses but improving product quality and experience.

Cultivator Implementation Steps

1. Optimize Water Activity Levels:

   • Maintain water activity between 0.45–0.65 aW during drying and curing. This range maximizes terpene and cannabinoid yields while minimizing microbial growth risks.

   • Water activity should be adjusted carefully, with higher moisture (up to 9% MC) for better terpene retention and smoother smoke.

     
     

2. Post-Harvest Drying and Curing:

   • Use controlled drying techniques to achieve optimal moisture content (5%-9%) without over-drying or excessive moisture that could lead to microbial contamination.

   • Implement humidity control packs (e.g., Boveda) during curing to ensure consistent moisture levels and preserve both cannabinoids and terpenes.

   • Consider vacuum-sealed packaging or airtight storage to prevent moisture fluctuations that could degrade product quality.

     
     

3. Managing Consumer Experience:

   • Aim for lighter ash color and a less irritating smoking experience by targeting higher water activity (around 0.65 aW) in the curing process. This will cater to consumers who prioritize smoother, less irritating smoking.

   • Regularly evaluate consumer feedback on the smoking experience to ensure product quality aligns with expectations.

     
     

4. Balancing Financial and Quality Considerations:

   • Consider the financial implications of lower moisture content (0.45 aW) as it can result in 18.14 grams per pound weight loss. While this may reduce weight, the improved smoking experience could justify the loss, especially for higher-value products.

   • Factor this weight difference into cost structures to ensure profitability while maintaining quality.

     
     

5. Health and Safety Considerations:

   • Avoid water activity above 0.65 aW to minimize the risk of microbial growth and product contamination.

   • Investigate further into elemental concentrations like sulfur and phosphorus in cannabis ash, which may affect consumer health, and adjust cultivation or fertilization practices accordingly.

     
     

6. Consumer Education:

   • Educate consumers about the benefits of optimized water activity for a smoother, more flavorful smoking experience. Provide transparency about how water activity influences ash color, irritation, and product quality.

     
     

7. Future Research and Innovation:

   • Engage in ongoing research into the health implications of elevated sulfur and phosphorus in ash.

   • Participate in collaborative studies to explore how different drying, curing, and storage methods affect product quality and consumer preferences.

By focusing on water activity management, cultivators can improve both the quality and profitability of their cannabis products. The balance between optimizing moisture content, enhancing terpene yields, and maintaining consumer health and safety is key to ensuring a high-quality, consistent product that meets both regulatory standards and consumer expectations.

READ THE FULL PUBLICATION HERE