What extraction method works best for extracting the most terpenes?
As far as I know, if you want to extract only full spectrum terpenes, and preserve the flavor profile of the original plant material as much as possible, then steam distillation is the way to go.
My dream process is as follows:
Step 1: Steam distill full spectrum terpenes.
Step 2: Re-dehydrate your biomass.
Step 3: Crude extract biomass.
Step 4: Winterize crude extract.
Step 5: Distill winterized extract.
Step 6: Homogenize your steam distilled full-spectrum terps from the original plant material back into your THC distillate.
Step 7: Dab it.
Step 8: Order a pizza and watch re-runs of Scooby Doo.
Distillation would be the way to go. Adding a cold trap inbetween the oven and pump will score you some more.
Using a cold trap to capture terpenes released from high vacuum fractional distillation, like you would use to fraction off THC, often results in partially denatured terpenes which do not taste as good as the terpenes from the original source material. This goes for ovens too. Terpenes are fragile molecules and should be handled carefully. Like I said if you want to preserve the original terpene profile and really get the best tasting results, steam distillation all the way.
I cant help but think about this alot in the concentrates field. Now this is just my opinion as I am no extraction guru, lol, but with live resin, I noticed immediate terpene expression in flavor that has been unmatched flavor-wise with old traditional heat pressing.
Many, many, many extracts retain the flavor of the carrier used to extract from my experience. I am very peculiar about flavor profile being that i am very attentive with flower, that alterations in flavor is very noticable to me, thus putting me off to consuming concentrates used with chemical extraction.
I honestly would suspect, in my educated guess, that your steam process may very well save those critical terpenes in processing!