RogueRose
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Does Chemistry have the answer? Cleaning fats/oils by boiling - strange reactions
I have to use lard, tallow and other animal fats for some of the products I make so this requires me to render the fats. The problem is that they
need to be cleaned and purified before use. There are two main methods I use to turn the fat into the oils - chop up and boil in water or chop up and
heat in oven on as low a temp as effective (higher temp = faster but lower quality product).
I seem to get off-colored fats - mainly working with red meat. It gets brownish. So I try to clean by boiling with equal parts of water and then
filter in very fine paper (sometimes use papertowels or coffee filters) or very fine socks (for first filtering).
The problem with boiling is the oil seems to get really "angry" (sound of boiling VERY vigoursly, like putting frozen ice coated fries in super hot
fryer) and shake the pot violently, especially if I put a lid on the pot (thinking the condensed H2O on inside of lid drops into 212+ degree oil on
top and turns to steam again). Sometimes the temp has risen to like 230+ wile there was water in it (scared crap out of me) but wasn't steaming very
much - stirred with spoon attached to long stick. All of this seems more pernounced when I cook outside on very hot wood fire (heats sides of pot
much more).
The water/oil doesn't always make the "angry" sound when boiling. It seems to take some time to happen when put on the stove. The strange thing is
if removed from heat for like 2 hours (and add at least as much H2O that had evaportated, probably more) and then put back on stove, the "angry"
sound comes back either immediately or a few mins upon reaching boiling point.
What I really need to do is find a way to clean this fat to get as white and less smelly, as possible. If filtering through micron level filter is
better, I can look into that but I had good success with by previous methods (wasn't doing as much volume though).
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Sulaiman
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I think that you could dissolve the fats out by soaking in a suitable solvent
(e.g. petroleum, acetone, alchohol)
for small scale the solvent can be evaporated away / lost
for larger scale solvent recovery may be worthwhile.
Just musing ... I have not done this.
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Artemus Gordon
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Fat is often used as a cover layer to prevent meat dishes from spoiling. The usual way to get purified fat is to, 1. Remove as much meat from your fat
as possible with a knife, 2. Boil gently, uncovered, in a casserole dish or other pot with a wide top opening, 3. After boiling for perhaps an hour,
let the pot cool to room temp., then put it in the refrigerator. The fat will congeal in a solid white layer on the top, while the meat proteins and
such should remain in the water. Lift off the solid fat, and rinse it under cold water, then you should have quite pure fat.
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feacetech
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So are you rendering viscera to get tallow. Or are you trying to clean up tallow.
If your making tallow look up.
eye wells
screw press
centrifugal separators
MIRNZ Low temperature rendering
http://www.mirinz.org.nz/pubs/bulletins.asp
http://www.meatupdate.csiro.au/infosheets/Rendering%20-%2019...
Has some articles on meat processes
Fresh undamaged rendering material will make Tallow with the Lowest FFA content, cleaning the paunch will help remove the green colour you can get and
improve bleach colour and FAC
Typical chemical tests for tallow
FFA (free fatty acids), heat in ethanol and titrate with NaOH
Moisture, 100 C for 3Hours
FAC (Free available colour) measure a against a standard colour wheel
Bleach test, heated at 115 C with bleaching earth (45mins) while mixing filtered and compared against standard colours
Lipid peroxide Value, too long to remember also an extremely variable test
Slowly heating discoloured tallow will bleach it.
Heating Tallow with bleaching earth and filtering it will make it a nice colour.
Tallow is Graded mainly on bleach colour (measured in red units), and FFA content.
the AOCS (American Oil Chemists Society) will have more tests
I have an old AOCS vol 1 and Vol 2 if you want any tests scanned
Personal experience I found fats extracted with pet ether 40-60C had a nasty smell this was extracted from the meal part of the process however.
Use clean fresh product, don't ignore viscera it has the best fat.
Industrially they remove the solids and water you can read more in the links.
I would say try press the fat out through a screen to remove as much protein and solids as possible, dry or separate the water, bleach (with bleaching
earth) then filter. More bleaching earth and time will make the colour better and better
I use to be able to bleach bright green tallow to a nice white looking fat although when put on a comparator it could be anything from <1.0 red
grade to K grade >1.5 red based on the standard test (100g of tallow 15g of earth and 45 min bleach @ 115C)
[Edited on 20-12-2015 by feacetech]
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