November 15, 2022

Use of X-ray Irradiation for Inactivation of Aspergillus in Cannabis Flower
Stephen Frink, Olivera Marjanovic, Phoi Tran, Yun Wang, Weihong Guo, Noahie Encarnacion, Donelle Alcantara, Bahman Moezzi, Gordon Vrdoljak

The study focuses on the potential of X-ray irradiation for inactivating four pathogenic species of Aspergillus (A. niger, A. flavus, A. fumigatus, and A. terreus) in cannabis flower. These species are important human pathogens and their presence in cannabis flower and products may pose a threat to human health. The researchers found that X-ray irradiation at a dose of 2.5 kGy is capable of rendering Aspergillus cells non-viable at low, medium, and high levels of inoculation. The X-ray treatment of cannabis flower did not significantly alter the cannabinoid or the terpene profiles of the flower samples. Therefore, X-ray irradiation may be a feasible method for Aspergillus decontamination of cannabis flower. However, more work is required to determine the consumer safety of irradiated cannabis flower and cannabis products (Page 1).

The article also discusses the context of cannabis use and the need for safety measures. Cannabis sativa L. plants host a number of microorganisms, including bacteria and fungi that could be harmful if ingested or inhaled. The presence of Aspergillus in cannabis can lead to life-threatening systemic fungal infections, especially in immunocompromised individuals. Therefore, ensuring the safety of medical cannabis is imperative for critically ill patients (Pages 2-3).

The authors also discuss various methods of decontaminating medicinal plant materials while still retaining their bioactive properties. They highlight the advantages of ionizing radiation for sterilizing plants for medicinal use. It is considered a cold pasteurization technique as it minimally raises the temperature in the product being sterilized, leaves no chemical residues behind, and preserves the product quality and characteristics (Pages 2-3).

Impact on Cannabinoid Profile

Page 10 of the document discusses the impact of X-ray irradiation on the cannabinoid profile of cannabis flower samples. Here are the key points:

The major cannabinoids found in the flower samples were Delta 9-THC (~70% peak area), CBG (~ 3% peak area), CBC (2.5% peak area), CBN (2.5% peak area), and THCV (0.7% peak area). There was a slight increase in CBN amount as the treatment doses increased. CBN is an oxidation and degradation byproduct of the Delta9-THC and the slight increase may be due to a slight increase in temperatures at higher levels of the X-ray treatment. There was also a slight increase in cannabifuran amount at the highest treatment dose level.

The temperature in the X-ray chamber was monitored during the X-ray irradiation process, which was slightly elevated to around 28°C compared to the 23°C at the beginning. This slight elevation of temperature did not seem to cause accelerated decarboxylation of the THCA to THC nor degradation of the THC to CBN in the sample, as there is no trend observed for changes in the THCA and THC concentrations.

Cannabinoid Concentration of Flower Samples Band after X-ray Irradiation Treatment at Different Dosage Levels

dose (kGy) mg/gmg/g mg/g mg/g mg/g mg/g mg/g
0.0 (untreated) 0.623 0.298 1.10 0.558 38.9 140 0.959
0.5 0.654 0.311 1.20 0.649 42.5 154 1.12
1.0 0.670 0.313 1.21 0.663 42.6 154 1.12
1.5 (for mold) 0.680 0.307 1.21 0.688 42.9 157 1.16
2.0 0.665 0.313 1.19 0.694 41.5 153 1.11
2.5 (for aspergillus) 0.632 0.2821.06 0.662 37.6 140 1.01

Note:  CBD was not detectable in the untreated samples.

Impact on Terpene Profile

The impact of X-ray treatment on terpenes in cannabis flower is discussed on page 12 of the document. The major terpenes found in the flower samples were Caryophyllene, Beta-Panasinsene, Eudesma-3,7(11)-diene, Alpha-Humulene, Alpha-Bisabolol, Linalool, and Fenchol.

The researchers observed a slight downward trend for Caryophyllene, Beta-Panasinsene, and Eudesma-3,7(11)-diene with X-ray treatment. Alpha-Humulene had a lower level at the highest treatment level (5.0 kGy). These changes were not tested for statistical significance. The authors suggest that these small changes may reflect the slight increase in temperatures at higher levels of the X-ray treatment.

However, they also noted that there were no observed changes for Alpha-Bisabolol and Fenchol.

Overall, the study concluded that X-ray treatment of Aspergillus contaminated cannabis flower at 2.5 kGy has minimal effects on terpene concentrations.