U of S | Mailing List Archive | alt-photo-process-l | Re: gum arabic

Re: gum arabic

Alberto, I was just looking at the kremer site as well, and noticed that least one of their types of gum was described as a mixture of acacia senegal and acacia seyal; myself, I'd prefer pure acacia senegal.

A slight clarification; when I said kordofan and acacia senegal are the same, I meant that kordofan is acacia senegal, not that all acacia senegal is kordofan. Kordofan is technically acacia senegal from a particular region, although I don't think it really matters where the acacia senegal is from, as long as it's acacia senegal. Some time back, most of the acacia senegal came from senegal, hence the name. In more recent years almost all the acacia senegal came from Sudan, but now only about 50% of it is grown there, now much of it comes from other subsaharan countries.

On Jan 17, 2009, at 9:18 AM, Alberto Novo wrote:

Also, sort is important; the kordofan, labeled (1) will be a higher (finer) sort than the other, at sort 3. Hope that's helpful,

As for Kremer's gum arabic, their pdf on their gum details is the same for the three qualities, though their prices are different, so I am wondering what they really are. I am not buying from Kremer, because I have about 1 kg of gum arabic of unknown origin since a long time (though it works well).
About Acacia senegal (cited from Kremer pdf):
"Gum Arabic is a dried exudate obtained from the stems and branches of Acacia senegal (L.) Willdenow or closely related species of Acacia (fam. Leguminosae). A. seyal is a closely related species. Gum arabic consists mainly of high-molecular weight polysaccharides and their calcium, magnesium, and potassium salts, which on hydrolysis yield arabinose, galactose, rhamnose, and glucuronic acid. Items of commerce may contain
extraneous materials such as sand and pieces of bark which must be removed before use in food. Gum arabic from A. seyal is sometimes referred to as gum talha."
"Gum Arabic from A. senegal is a pale white to orange-brown solid, which breaks with a glassy fracture. The best grades are in the form of whole, spheroidal tears of varying size with a matte surface texture. When ground, the pieces are paler and have a glassy appearance. Gum from other acacia species may not have the characteristic tear shape and are often darker in colour. Gum from A. seyal is more brittle than the hard tears of A. senegal."
One among the differencies (not easily testable at home) is their optical properties: water solutions from A. senegal are levorotatory, from A. are dextrorotatory.