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Q: Processing of marine algae ( Answered 5 out of 5 stars,   0 Comments )
Subject: Processing of marine algae
Category: Science > Chemistry
Asked by: jonbollom-ga
List Price: $3.00
Posted: 05 Dec 2003 12:49 PST
Expires: 04 Jan 2004 12:49 PST
Question ID: 283918
How is agar processed / refined / extracted from sea-weed to a powder
suitable for sale/delivery to a factory for incorporation into
products such as cosmetics, paints etc?
Please refer me to a publication that details the answer.

Request for Question Clarification by pafalafa-ga on 05 Dec 2003 13:14 PST
There's a brief description here:

(click on "Agar")

but I haven't seen anything more detailed.  What level of detail are you seeking?

Clarification of Question by jonbollom-ga on 07 Dec 2003 16:11 PST
The sort of detail I am looking for is akin to a cooking recipe or the
instructions a pupil would get in a chemistry lesson at
school...which, having viewed the link you provided, may be a more
complicated issue than I realised.
Thus I will accept the link you (pafalafa-ga) supplied as sufficient
answer, if you post it as such. Any extra would be a welcome bonus.
Thank you pafalafa.
Subject: Re: Processing of marine algae
Answered By: pafalafa-ga on 07 Dec 2003 19:17 PST
Rated:5 out of 5 stars
Hello Jon,

Thanks for your nice post...glad to hear that the link I provided was
useful.  Here's another with some additional details about agar


Seaweed is generally harvested by one of three methods: water
collection by divers in pressurized suits; raking of intertidal
seaweed beds; and by beach collection of weed tossed on shore by
storms and tides...

After harvesting, the wet weed is washed in fresh water, where
available, and spread out to dry. The sun may partially bleach the
weed as it dries. When the moisture content drops below 20%, the dried
weed is baled. Depending on the harvesting method used, the dried weed
can contain unwanted seaweed species, shells, and/or sand.

Traditionally, agar is extracted by a labor-intensive method wherein
the dried seaweed is washed and pounded to remove sand, shells and
unwanted species (which may be toxic to bacteria and cells in
culture). The weed is then boiled for a period of up to 15 hours. The
liquor pH is controlled by the addition of calcium hypochlorite and
sodium bisulfate. The entire "cook" is then strained through 3mm mesh
cloth, and the cake is pressed and retained for recooking. The
strained liquor, containing approximately 1% agar, is cleared somewhat
by sedimentation, after which it is allowed to solidify as it cools.

In earlier times, gelled agar was produced by allowing it to freeze
and thaw outdoors during the winter months. During the thaw cycles,
unwanted soluble salts, nitrogenous materials and color were leached
from the agar. Newer methods for agar manufacture employ
counter-current and multiple cascade extraction, centrifugation,
plate-and-frame press filtration, artificial freezing and chemical
bleaching methods to purify the agar. Although each manufacturer uses
their own modifications of the basic extraction-freeze-thaw process, a
common industrial agar processing sequence is as follows:

1.Cleaning raw material.......6.Gelation............. 11.Sterilization 
2.Chemical pretreatment.......7.Freezing/Syneresis....12.Bleaching 
3.Hot water extraction .......8.Post-treatment........13.Washing 
4.Chemical post-treatment.....9.Washing ..............14.Drying 
5.Filtration ................10.Drying 


Hope that helps.  Let me know if you need any more information.


search strategy:  Google searches on:

"agar processing"
"agar manufacturing"
jonbollom-ga rated this answer:5 out of 5 stars

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