Cov roj tseem ceeb yog muab los ntawm cov nroj tsuag uas muaj cov qog balsam thiab yog cov nroj tsuag zoo ib yam. Cov tib neeg feem ntau siv cov lus rho tawm lossis rho tawm los sau cov txheej txheem ntawm cov roj yam tseem ceeb. Txawm li cas los xij, "Extract" thiab"Kev rho tawm"lawv tus kheej yog ob lub tswv yim sib txawv.
Extract txhais tau tias kom tau los ntawm refining. Kev npaj cov khoom xyaw uas muaj txiaj ntsig (xws li cov khoom xyaw lossis kua txiv hmab txiv ntoo) los ntawm cov khoom siv los ntawm kev kho mob nrog cov kuab tshuaj (xws li ethanol), distillation, lub cev qhuav dej, raug rau siab lossis centrifugal quab yuam, lossis lwm yam txheej txheem tshuaj lom neeg lossis cov txheej txheem.
Txoj kev rho tawm cov roj tseem ceeb tshaj plaws yog: distillation, txias nias, hnyav extraction, roj sib cais, thiab lwm yam. Thawj ob yog cov tshuaj tiv thaiv lub cev uas siv cov txheej txheem siv tshuab yam tsis muaj cov khoom siv dag zog ntxiv. Lawv yog cov feem ntau siv txoj kev rau extract cov ntshiab cog tseem ceeb roj. Ob lub tom kawg yog tsim los ntawm cov txheej txheem tshuaj hu ua extraction.
Extraction: Ua nrog cov kuab tshuaj kom tshem tawm cov tshuaj soluble lossis siv cov kuab tshuaj kom tshem tawm cov khoom tsis zoo. Cov kuab tshuaj hu ua kua yog hais txog cov kua uas tuaj yeem yaj lwm yam tshuaj. Nws muab faib ua cov kuab tshuaj organic thiab cov kuab tshuaj inorganic raws li nws cov tshuaj muaj pes tsawg leeg.
Cov txheej txheem ntawm extraction yog siv qhov sib txawv ntawm solubility los yog muab faib coefficient ntawm ib tug compound nyob rau hauv ob qho tib si immiscible (los yog me ntsis soluble) cov kuab tshuaj kom hloov cov compound ntawm ib qho hnyav mus rau lwm tus. Thaum kawg, rov muab rho tawm yuav tsum tau rho tawm feem ntau ntawm cov tebchaw.