[alt-photo] The Gum Arabic Report (was: Re: Re: evaporation of gum mixture)

[Katharine Thayer]

Suffering from a strained back and having no plans for the holiday  
beyond reading David McCullough's biography of John Adams and  
listening to Aaron Copeland's American-themed music, I spent some  
time yesterday trying to find out more about the structure and  
properties of Acacia seyal.  I learned very little about that, but  
found myself drawn into a fascinating study of the political  
maneuvering around the labeling and marketing of gum arabic.  Since I  
was researching on the internet, I didn't get a full picture of  
course, only intriguing bits and pieces.

Some of the things I found out that might be interesting for gum  
printers to know:

A. seyal until fairly recently has been a very small part of the gum  
market, like 5% or so.  Now, it represents fully half of the gum  
arabic market.

  Prior to 1998,  the label "gum arabic" was reserved for gum from  
Acacia senegal "and closely related species."   In 1990,  a sentence  
was added to the definition that specified that the the solution must  
fall within a specific optical rotation range,  that effectively  
excluded A. seyal.  (A. senegal is levorotary; A. seyal and some  
other A. species are dextrorotary).

In a series of political maneuvers in 1998-1999 at meetings of the  
JECFA (Joint Expert Committee on Food Additives) and the Codex  
Alimentarious Advisory Commission,  the rotation specification was  
dropped and the definition was expanded to  specifically include A.  
seyal, with additional language specifying that the two are not  
technologically equivalent  and can be distinguished by immunoassay.   
This expansion of the definition of gum arabic was opposed by Sudan  
(which has historically controlled the market in A. senegal) but  
supported by other gum-producing nations like Chad and Nigeria, which  
produce more A. seyal than A. senegal.  But in the final approval the  
qualifying language was stripped off and the final approved  
definition of gum arabic, still in  place, reads simply:

     "Gum arabic is a dried exudate obtained from the stems and  
branches of  Acacia senegal or Acacia seyal
(fam. Leguminosae)."

While it is politically advantageous for talha-producing countries to  
have achieved the inclusion of Acacia seyal in the definition of gum  
arabic (thereby effectively allowing its use for foods)  it is  
generally agreed in the trade that gum talha is an inferior product.   
As one report put it, "Talha is substantially cheaper than hashab (A.  
senegal) because it has inferior technical properties for some of gum  
arabic's uses, such as in the soft drinks industry..."  and exporting  
countries typically assign A. seyal a lower grade than A. senegal.

I was not able to find much information about the properties of  
talha, except that in raw form it is more friable (crumbles easily in  
the hand) and doesn't tend to form hard tears as A. senegal does,  
that it is dextrorotary, that it contains more tannins, that it  
exists in two forms: reddish and white.  How it performs in gum  
printing there is of course no available data on, other than Tom's  
anecdotal report, and I'll look forward to a further report.  Talha  
has become the gum of choice for health-food and alternative medicine  
uses, probably because it's historically been cheaper than A. senegal.

I did come to the conclusion that I was wrong about Kremer's gum.  I  
had assumed that because they described their gum arabic as coming  
from A. senegal or A. seyal, that they meant that if you bought gum  
arabic from them, it might be either A. senegal or A. seyal.  Now it  
seems clear to me that their description is simply copied from the  
official definition of gum arabic:  "Gum arabic is the dried exudate  
from A. senegal or A. seyal."  However, they provide sufficiently  
specific specifications to establish that their gum arabic is indeed  
A. senegal, based on the optical rotation.   IMO, they should either  
drop their use of the official definition of gum arabic, or if they  
are going to keep it, they should at least make it clear in the  
product description that while officially, gum arabic can either be  
A. senegal or A. seyal, the gum arabic they sell is A. senegal.

As to Daniel Smith, I have no idea.  All I know is that this gum  
behaves differently than other gums I've used. It prints the same; it  
prints beautifully, in fact,  but physically, it behaves differently,  
it seems like a different gum than  the others I've used.  So it  
seemed logical to wonder if it's actually a different species of  
Acacia, but as I said, it's just a suspicion which I have not been  
able to confirm or disconfirm.

I always thought the size of the crop depended on weather conditions  
and disruption in areas of conflict and stuff like that, but it turns  
out that while those factors do play a part,  the thing that has  
affected the available supply more than anything has been policies  
set by the Sudan government-run monopoly gum exporting company (which  
has since been racked with corruption charges and effectively shut  
down as a government monopoly)   that have resulted in the farmers  
being paid so little for the gum that it wasn't worth their while to  
harvest it, and many farmers have cut the trees down to make room   
for other crops.  An industry market report from March 2010 warns "A  
very poor gum acacia crop this year, raising huge concerns about gum  
prices once the old stocks are depleted. Furthermore, low gum prices  
in Sudan mean that farmers have no incentives to tap trees and have  
pursued alternative sources of income. As a result, a large  
proportion of gum acacia trees remain untapped, drastically reducing  
the size of the crop."  A Sudan government announcement the same  
month proclaimed that Sudan's output of gum arabic had reached 49,000  
tons for the season, which would be a good total for a good year, but  
this seems fanciful election rhetoric, given that the industry market  
report for June continues dire:  "The price increase trend of A.  
senegal continues as the quantities of incoming raw gums keep  
dwindling.  We foresee that this will remain the case.  The supply of  
Hand Picked Select (the highest grade of A. senegal) is extremely  
limited, will not meet demand, and will remain very high priced."

The price of A. senegal in contrast was very low from 1998-2003 or  
so; let's hope that our suppliers loaded up during those years of  
cheap gum and won't have to buy while the price is high.

I just think this is all very fascinating, and share it for whatever  
it's worth to anyone else.  There's a lot more, but that's probably  
really enough for now, and as I said, this is just bits and pieces  
I've pulled off the internet, hardly a full account, but I really do  
think someone should write that book.
Katharine



On Jul 4, 2010, at 9:07 AM, Tomas Sobota wrote:

> Some months ago I posted here about an experiment I made with gum  
> talha
> (Acacia seyal). I received a small quantity from friends in the  
> Sahrawi
> camps in southern Algeria, where the tree also grows.
>
> I prepared and used this gum just like senegal, with totally  
> disappointing
> results: all the gum coat seemed to harden and hence, no image.
>
> This test was just a fast experiment, so I cannot swear that some  
> other
> variable didn't get in the way. Now that you remind me, I will try  
> again in
> more controlled circumstances.
>
> Gum senegal in stones (you call them "tears" but what is sold here  
> is so
> large that it could only be called crocodile tears) is very easy to  
> get
> here, and reasonably inexpensive, that's one of the reasons that I  
> buy it
> instead of prepared gum. Also, the work is not that much: the gum  
> dissolves
> easily during a night or less.
>
> Tom Sobota
> Madrid, Spain
>
> On Sun, Jul 4, 2010 at 5:25 PM, Katharine Thayer  
> <kthayer at pacifier.com>wrote:
>
>
>>
>> On Jul 3, 2010, at 1:22 AM, Tomas Sobota wrote:
>>
>>  I have never used prepared gum solution. I prepare gum in the  
>> original
>>
>>> artisanal way, dissolving gum arabic stones in water. Then, I  
>>> keep the
>>> solution in dark glass bottles, well stopped and preserved with a  
>>> few
>>> thymol
>>> crystals. Kept in this way, I have never observed any  
>>> evaporation, not
>>> even
>>> in a time span of years. So, what is being described is strange, and
>>> probably related to the way that the commercial gum is prepared or
>>> preserved.
>>>
>>>
>>
>> Well, it may be more than that.  I've expressed my suspicion  
>> before that
>> the Daniel Smith premium gum may be partly or wholly a different  
>> acacia
>> variety (acacia seyal)) since it behaves differently from other  
>> gums I've
>> used, not only in this tendency to dry out  but in other ways that
>> correspond to the description of acacia seyal.  I tried to verify or
>> disconfirm this suspicion with Daniel Smith but couldn't get an  
>> answer from
>> them.   But Kremer, for example, does (or did, last time I looked)  
>> specify
>> that some of their gum arabics are  a mixture of acacia senegal  
>> and acacia
>> seyal, or even acacia senegal OR acacia seyal.  Like Daniel  
>> Smith,  other
>> suppliers (Bostick & Sullivan, Photographer's Formulary) don't  
>> specify the
>> acacia variety used in their "gum arabic" (apparently there's no  
>> requirement
>> that "gum arabic" be acacia senegal.
>>
>> I agree, mixing your own from tears is probably the best way to  
>> get the
>> right kind of gum; the reason I don't  has been laziness I  
>> suppose, not
>> wanting to bother with the effort of searching out a supply of  
>> good quality
>> tears of the right variety in the right grade (maybe this is more  
>> easily
>> done on your side of the ocean?) combined with the ease of use of
>> commercially prepared gum.  I did buy some powder from Daniel  
>> Smith and mix
>> it, but if their prepared gum isn't entirely acacia senegal, the  
>> powder
>> probably isn't either.  I haven't had an opportunity to use that  
>> gum yet,
>> since I've been in the hospital three times in the last year for
>> heart-related surgeries and explorations and have been deeply  
>> involved in
>> another project in the meantime.
>>
>> Curious, I started searching online for gum acacia senegal in tear  
>> or lump
>> form, just to see how difficult it would be to take this approach,  
>> and found
>> that it's not that simple. I went down three pages of google hits  
>> and found
>> basically wholesale distributors with minimum orders of from 100  
>> kg to 6000
>> kg, and in places like China.  In this group I found several  
>> distributors
>> who list their A. senegal as grade 1 and A. seyal (aka "gum  
>> talha") as grade
>> 2 or 3, FWIW.    I also  learned that the US imports largely  
>> processed gum
>> and European countries impor largely lump gum, processing the gum and
>> reselling it to the US in processed form.   Which might explain  
>> why it's
>> easier to find lumps of gum in Europe than it is in the US.
>> Katharine
>>
>>
>>
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