Sciencemadness Discussion Board

yellow pigment in lemon: extraction

jamit - 25-1-2017 at 09:42

does anyone know of any extraction that can be done to get the yellow pigment in lemon? There's nothing on google search nor in this forum.

Has anyone tried to extract the pigment of plants and fruits (oranges, roses, etc.) Just like you can get the pigment from red cabbage, I'm trying to isolate the color pigment in lemon -- beautiful yellow color!

If you can direct me to the right source or suggest some ideas, it would be much appreciated!

PHILOU Zrealone - 25-1-2017 at 09:51

Lemoncello liquor is yellow because of it; maybe it is a way to get it?

Boffis - 25-1-2017 at 10:35

Hi Jamin, I am not sure where to start looking for the data you need but there are several journals specifically about natural products. Here are a few thoughts.

The pigments in lemons and oranges are probably either carotenoids or flavin/flavin glucoside type. If they are the former they are likely to be soluble in the less polar to non-polar organic solvents like chloroform, cyclohexane and petroleum ether, unfortunately so are the fixed (fatty) and volatile (smelly) oils. The flavin type are more soluble in the polar organic solvents like alcohols but again these will extract the volatile oils and part of the fatty oils too. Bitter orange and grapefruits contain various flavinoid glucosides that make them bitter tasting so they may also contain the free flavins. You can test this by extracting a little peel with alcohol and then placing a drop of alum solution on a piece of filter paper followed by a couple of drops of the alcohol solution and then either dilute ammonia or very dilute sodium hydroxide solution, most flavins will generate a more fluorescent yellow spot where the alum was than the surrounding wet area (needs a UV light). The carotenoids generally do not produce fluorescent lakes.

I think the best way to extract the peel is to put it in a food processor and then dry it in the oven to drive of the volatile oils first before trying to extract with various solvent. You also try steam distilling the pulp to remove the volatiles and if you add a few drops of sulphuric or hydrochloric acid they will help liberate the flavin type pigments from there glucosides.

j_sum1 - 25-1-2017 at 16:33

I would guess that chromatography is the go-to separation technique for compounds such as these. (Note that this is pure unreferenced speculation of a kind that would make deltaH proud.)

I have noticed from culinary exercises that the compounds in question are sensitive to temperature. Lemon peel discolours on heating. I'd be looking first of all for a suitable solvent and proceeding from there.

AvBaeyer - 25-1-2017 at 21:05

Jamit,

The color is largely due to carotenoid compounds and to some extent flavonoids. The yellow color of lemons is easily extracted with ethanol along with the oils and other things. This was already mentioned in a post above. You may find the attached paper useful in your pursuit.

I find your interest in natural colors interesting. My own interest in chemistry started more than 50 years ago by trying to extract the colors from my mother's flowers in her garden.

AvB

Attachment: Carotenoid Biosynthesis in Citrus.pdf (611kB)
This file has been downloaded 366 times

jamit - 27-1-2017 at 07:45

Quote: Originally posted by Boffis  
Hi Jamin, I am not sure where to start looking for the data you need but there are several journals specifically about natural products. Here are a few thoughts.

The pigments in lemons and oranges are probably either carotenoids or flavin/flavin glucoside type. If they are the former they are likely to be soluble in the less polar to non-polar organic solvents like chloroform, cyclohexane and petroleum ether, unfortunately so are the fixed (fatty) and volatile (smelly) oils. The flavin type are more soluble in the polar organic solvents like alcohols but again these will extract the volatile oils and part of the fatty oils too. Bitter orange and grapefruits contain various flavinoid glucosides that make them bitter tasting so they may also contain the free flavins. You can test this by extracting a little peel with alcohol and then placing a drop of alum solution on a piece of filter paper followed by a couple of drops of the alcohol solution and then either dilute ammonia or very dilute sodium hydroxide solution, most flavins will generate a more fluorescent yellow spot where the alum was than the surrounding wet area (needs a UV light). The carotenoids generally do not produce fluorescent lakes.

I think the best way to extract the peel is to put it in a food processor and then dry it in the oven to drive of the volatile oils first before trying to extract with various solvent. You also try steam distilling the pulp to remove the volatiles and if you add a few drops of sulphuric or hydrochloric acid they will help liberate the flavin type pigments from there glucosides.


Thank you for starting me on the right track? I will try that.

jamit - 27-1-2017 at 07:46

Quote: Originally posted by AvBaeyer  
Jamit,

The color is largely due to carotenoid compounds and to some extent flavonoids. The yellow color of lemons is easily extracted with ethanol along with the oils and other things. This was already mentioned in a post above. You may find the attached paper useful in your pursuit.

I find your interest in natural colors interesting. My own interest in chemistry started more than 50 years ago by trying to extract the colors from my mother's flowers in her garden.

AvB


Thank you for the article! Very helpful.