Putting a clend of spices in a tied up spice sachet is fairly common way of keeping wonderful spices that flavor food, but are not edible in the cooking process.
Of course, as a chemist, whn doing analysis, such a thing was not eard of.
What usually happened was an extraction of what i wanted and that was used in whatever process that needed to happen.
Things can go wrong otherwise.
Applied to cooking means that those flavorful items that you which to add to your cooking,
usually things like bay leaf, pickling spice, pepper corns, etc., etc., can have those flavors extracted.
Most of the intense flavors are water soluble (disolve in water) and even more so in hot or boiling water, so...
what i do is boil those spices i do not wish to remain in the dish when i serve and then add the liquid to what i am cooking.
Simply porung the boiling liquid through a strainer and you have the flavor, but not the unedible bulk.
No more sachets for me!