I have made an experiment to see whether grinding rue seeds is really necessary. I have also tested whether PC can reduce the cooking time.
I made three samples from 100 g of rue:
1) The seeds has been first cooked in a PC at 0.7 bar for 15 minutes three times.
2) The seeds from 1) has been washed and then cooked for 30 minutes three times at normal pressure.
3) Finally, the seeds from 2) has been ground/mushed in a powerful blender with fresh water and cooked the same way as 2.
All three samples has been filtered with loose cotton, the filtrate reduced to about 1/3 volume and filtered again with tight cotton.
Acetic acid has been added to the suspended ground seeds to ensure all the possibly liberated alkaloids are in salt form.
Here are all three samples:
The small beaker on the right is the sample #3 filtered through Celite. The ground/mushed seeds pass through cotton easily but immediately clogs paper or glass filters so I made only tiny amount of this to see any hard-to-see reaction when basifying.
I have prepared 10% NaOH solution and added to samples. The first sample reacted strongly and I needed about 15 ml of solution until no color change is seen:
The second sample also reacted but now I took less than 5 ml of base. This concludes some amount of alkaloids are still present even after three cookings in PC:
Finally the solution from boiled ground seeds haven't shown any reaction. I have added about 10 ml of base:
No reaction seen on the strongly filtered sample #3:
After several washes with fresh water and decanting the liquid, some precipitate can be seen in sample #3, but it's really minuscule:
Decanted precipitates:
Sample #1 shows lots of darker precipitate:
Precipitate from #2 is lighter and only fraction of the amount from #1, but still seems considerable:
Precipitate from #3 is negligible, there are only traces captured by the filter, not even possible to scrape without damaging the paper:
Finally, the samples #1 and #2 has been dissolved in 400 and 200 ml of hot 2% acetic acid, then 10% salt has been added, now waiting to crystallize HCl salt:
I will weigh HCl crystals both samples to compare.
ConclusionsThe yield increase by grinding rue seeds is negligible. Grinding 100 g of seeds added what seems to be less than 50-100 mg of alkaloids, which for me is not worth the extra struggle with filtering the mush (which requires over 6 filter changes whilts the whole seed tea required just 1 filter change).
The grinding produces very fine milky substance that passes through tight cotton filter and possibly prevents alkaloid precipitation. It also makes precipitation harder to see. Even four washes has not removed this milky/cloudy substance.
To save time, it seems sensible to first boil the seeds for 10-15 minutes once or twice in a pot, then pressure cook for about 10-15 minutes once or twice to squeeze the last bits out.
Instead of three to five 30 minutes boils (over 2 hours), we need only up to one hour for the acid cook.