The metabolites are sugers, suger alcohol,and amino acids mainly, but some organic acid also exist.

Dear Ashrafi,

Long with heat degredation as mentioned by Labra-Vazquez already, I suggest that the form of the dried product will have an effect on your result.  Surface area of your sample will be critical to achieving good dryness.  Simply heating concentrates to dryness and I suspect you will see a skin or crust form on the surface, and the extract will concnetrate to syrup.  Freeze drying helps with surface area as you have a "fluffy" powder at the end, however, trapped methanol means one of two things -

1. the solvents present caused some collapse of the powder - means you have a concentrate syrup which does not dry well.  Challenge is to remove the organic solvent first before freeze drying.  The range of boiling points and vapour pressures from chloroform to water is huge.  Can you remove the organic say with a rotary evaporator and then freeze dry only the water?  If you need organic in there to maintain solubility then add some tertiary butanol or 1,4-dioxane

2. the solvent is in a strong relationship with the metabolite - it's hard to remove, and good surface area, deep vacuuum and careful application of heat is generally the way to reomve it.  In freeze drying circles this is known as Secondary Drying.

The following link has a useful overview of technology and techniques:

http://www.spscientific.com/freeze-drying-lyophilization-basics/

Kind regards

Rob

Dear Rob, 

Thank you for your consideration. I only want to remove methanol from water:methanol mixture (chloroform is not mattered because it will remove by centrifugation). Metabolites are present in water:methanol fraction and I want to remove methanol from water without any use of vacuum instrument and then freeze dry it. 

Best regards