Here’s the equipment quote for the 153 CU LN2 blast freezer:
The employee I’m working with gave me a roughly calculated dwell time of 7 minutes. But it was under incorrect assumptions (70’F flower temp when loading the freezer). So, the dwell time when using an insulated cooler with dry ice immediately after harvest should be much shorter, maybe <5 minutes.
If they would accept it, does anyone from IL want to help their R&D for our industry by gifting them some fresh flowers?
From our emails:
Me:
Do you have customers using your blast freezer for flash-freezing fresh cannabis (e.g., in vacuum bags or material socks for butane extraction)? And if so, have they reported dwell times that work for them?
Them:
I have been speaking with another customer recently who has a similar product, but is not using vacuum bags or anything, and is wanting to put the product through one of our tunnel freezers. Despite Illinois (our company location) being a recreational state, this is a product that is hard to get large quantity of to use for testing to determine accurate dwell times, and has been an industry that has been having increased interest in our freezer products. The dwell times are different depending on the desired temperature out, which I have been doing math on this product anywhere from 0F to -20F. This is something I have estimated to have a dwell time (Going from 70F to 0F) of about 7min, but I am unaware of how accurate this is, or what the difference would be with the product condensed down into vacuum bags. I have not gotten any information back from any of the customers I have spoken with, and this is something I wish was easier for us to test with our freezers so that I could have more accurate information and data on this.
My apologies that I do not have all the data and knowledge that would be of more accurate use, and this is something I have brought up with our owner to see if there is something we could do within the legal standards to test this product with our freezers so we would have the right information.
Me:
No apologies are necessary. What you wrote is very helpful. If you want to test yourself, send me your address, and I’ll ship you a few pounds of flowers! (kidding) Once I collect dwell time data and other metrics, I’m happy to share them with you, mainly if you help me tweak and optimize my SOP with your blast freezer.
Regarding dwell time, the best growers will pre-chill the plant material with dry ice. So the plant material should be well below 70’F before loading into the blast freezer. Probably closer to freezing or below -20’C on the outside of the buds, and closer to 0’C (30’F) to 10’C (50’F) inside the thicker buds.
Here’s a typical optimized workflow for indoor cultivation companies making the best fresh frozen. The goal is to minimize the time plant material is exposed to room temperature. The following is on a per-plant basis for simplicity in my email; it’s scaled to hundreds or thousands of plants as needed:
- Harvest plants in the grow room
- Immediately place harvested plants into an insulated cooler with dry ice to pre-chill the plant material.
- Transport cooler to trim/drying room
- Remove a single plant and trim large fan leaves from the plant
- De-bud branches from a plant (typically with a bucker) and place buds into a separate insulated cooler with dry ice.
- Lghtly vacuum seal buds. Layer the buds, so the bag is reasonably thin to reduce freezing time and ensure buds in the center of the bag freeze at the same rate as the outer buds. Vacuum sealing minimizes the bud’s oxygen exposure and simplifies post-freeze handling.
- Place vacuum-sealed bags into a separate insulated cooler with dry ice
- Once enough vacuum bags to fill the blast freezer have been prepared, load the freezer
- Run the freezer to ensure the center of all buds to reach -20’C to -30’C as fast as possible.
Most growers would prefer the center of all buds to reach -20’C (-4’F) to -30’C (-22’C) during flash freezing. Currently, most growers would leave vacuumed sealed flowers in a dry ice-packed insulated cooler, -40’C, or -80’C freezer for at least 24-hours. But that’s probably overkill. While a dwell time of one hour has been found insufficient, if the cooler isn’t overpakced, a few hours under those conditions should be sufficient.
The YouTube link about FF 1-hour dwell time in a dry ice cooler is from the Cannabis Cultivation and Sceince podcast https://www.youtube.com/watch?v=UkQyTEYB7I8, when Dr. Russo discusses his study I posted here: Goodbye ice-water hash, hello dry ice kif? (Nope...)