Dear Dr Anil,

Perhaps you are working on distillation of aromatic plant roots/ rhizomes with good saponin content. Foam formation is a routine problem in distillation for some specific plants. E.g., you always have this problems if working on extraction of essential oil from plants in family like Zingiberaceae. Saponin are suppose to be responsible for formation of excess foam inside the flask. Either try to adjust pH of medium slightly acidic (add few drops of weak acid) as alkaline pH reported to increase the solubility of saponin in water or  add common salt into water before extraction. Also always use distilled water for extraction work. You may apply the steps as mentioned by Drs BRR Rao and Marta in their answers for better oil quality and recovery etc.

Best of Luck

Probably you need to use less plant material and if necessary do several extractions of the same material, in order to have enough essential oil. Or you must use a bigger ballon/erlenmeyer. 

Good luck

Do you mean formation of foam or hot water bubbling and jumping or rising up into the condenser tube? Try regulating the temperature and add few glass beads for the latter problem. If you observe foam formation (I am surprised because I have never observed foam formation with several aromatic plants), try distilling your plant biomass with distilled water. Anyway which species are you distilling? Try cutting your material into small pieces, or try to distill paste of the material or semi-dried/dried/powdered material. Check if these techniques solve your problem.

Dear Dr Anil,

Perhaps you are working on distillation of aromatic plant roots/ rhizomes with good saponin content. Foam formation is a routine problem in distillation for some specific plants. E.g., you always have this problems if working on extraction of essential oil from plants in family like Zingiberaceae. Saponin are suppose to be responsible for formation of excess foam inside the flask. Either try to adjust pH of medium slightly acidic (add few drops of weak acid) as alkaline pH reported to increase the solubility of saponin in water or  add common salt into water before extraction. Also always use distilled water for extraction work. You may apply the steps as mentioned by Drs BRR Rao and Marta in their answers for better oil quality and recovery etc.

Best of Luck

Use metal mesh on the flask throat...it will break the foam effectively going from the flask into the middle part of the Clevenger type apparatus (where you collect the essential oil during the distillation)...

Dear Dr. Chanotia

Interesting. Can you give some examples? I have distilled roots and rhizomes of different species but never encountered this situation. What about soapnut, shikakai-do they produce frothing during extractions?

Dear Anil

In which species and plant part did you encounter this problem?

the better way to avoid all problems is the steam distillation method, where the plant is separated from the boiling water

You can add few drops/ml of n- Pentanol to minimize frothing. It will not affect to your extract content and will be separated during distillation.  

Interesting post Dr. Mrs. Rathod. I appreciate to receive any reference or reprint on the subject of addition of n-pentanol to distillation water for minimizing frothing.

No reference. Suggestion from the seniors and experienced & used during the concentration of aqueous extract of plant. But this is the fact.

It would be a nice idea to work on it for a publication. Thanks and good luck.

I've seen certain laboratories using  heavy silicone oils (non-volatile)  to avoid frothing ( saponin) in hydro distillation,  but would not recommend this unless concrete evidence on volatility and reactivity is available. I would recommend the physical /engineering interventions suggested by other scientists. Also it is also important to maintain the condensation, as poor condensation can result in frothing and bumping during hydro-distillation. 

Mr.Rathod,

Won't the n-Pentanol disturb the composition of the essential oil?

I have experience for frothing problem in the preparation of plant aqueous extract only. May be possible by confirming the HPLC/ GC profile.  

I feel use of silicone oils can be an option to prevent frothing during the extraction of essential oils 

I use of silicone oils to prevent the message during the extraction of essential oils