Animal Fat Qualities/Composition

[CathyB]

I've seen so much information on using leaf/kidney fat for soap, and other information saying fat is fat, use it all.

I've been using all fats, just combining and rendering. But now I want to know more.

I've found this tidbit:

"The difference between hard muscle fat and kidney fat may not be all that apparent up front. They both can be quite stiff and look much alike. The real difference can seen during and following the rendering process.

Suet, as opposed to muscle fat, contains a higher level of a triglyceride known as glyceryl tristearate, otherwise known as stearin. The result is that suet has a higher melting point and congealing point than regular fat."

Source: Suet, Part two: What it is, What it isn’t, and What to Look For

From one of DeAnn's brilliant posts I find

Stearin is about the same as any other soap making fat as far as the amount of glycerin created when it's saponified. You can calculate it: Soapy Stuff: Glycerin made by saponification

Stearic acid is made by further processing stearin to break the fat molecules apart into glycerin and fatty acid molecules. The glycerin is removed and the fatty acids that remain are either sold as commercial grade stearic acid, which is a mix of mostly stearic and palmitic acids, or further refined. Stearic acid adds no glycerin when it saponifies.

And from Properties of soapmaking oils | Summer Bee Meadow | Handcrafted Soaps, Soapmaking knowledge and supplies for crafters I learned that Steric Acid is responsible for "Hard, long lasting bar, stable lather."

In terms of soapmaking, where does the preference for kidney/leaf fat come from? Is it related to the rendering process, or is there an actual biological/chemical basis for the preference?

In practical terms, has anyone experimented using just leaf fat and just body fat and found any differences in soap qualities?

 

[Arimara]

I lack the ability to do that testing. I will say that I ignore anyone and everyone that tells me that fat is fat, carbs are carbs, and protein is protein. That is not true at all for any of them because their chemical compostitions vary from source to source, even from within that same source (like the fats you mentioned). That said, the differences lay more in where on the body the fat is sourced.

 

[AliOop]

I just rendered my first batch of leaf fat into leaf lard. I will say that it rendered MUCH more easily and cleanly than non-leaf fat has in the past. It had way less odor and was much whiter. A cleaner fat is much less likely to go rancid than a fat that still has lots of other "bits" in it, including bits of bone, hair, muscle, collagen, etc. So from the perspective of rendering and long-term storage, my experience so far is that leaf lard is highly preferable to non-leaf lard in those areas.

From my understanding, leaf lard is highly preferable to non-leaf lard for making pastries and pie crusts, due to the neutrality of taste and odor, as well as better flakiness and mouth feel. That's why leaf lard commands double or more the price per pound, at least where I live.

Whether those benefits transfer to finished soap... I couldn't say and haven't found anything definitive on that issue. I just made my first batches of soap with this leaf lard, so it is too soon for me to know if I can sense any appreciable difference in the leaf-lard soap and the non-leaf-lard soap. I'll definitely report back but am guessing there will be little to no noticeable difference in the cured soap.

But I will still take the leaf lard over regular lard since it is soooo much easier and cleaner to render. And as long as I have a local source for it that is less than the cost of store-bought regular lard that has preservatives I'd rather avoid, the leaf lard will be my go-to.

 

[AliOop]

I should add that I also save fats from cooking, since we make a fair number of roasts and ribs. I strain off the fat into a container, and save it up till I have enough to clean for soap.

I generally know approximately how much is schmaltz, how much is tallow, and how much is lard. That lets me approximate the values for inputting into the soap calculator. But I don't worry too much about it. I still use all my regular additives and other oils, including vinegar, sugar, salt/SL, CO and CaO. I call it my Barnyard Medley recipe. Due to the variable amounts of the different fats, it isn't as consistent as some of my more refined recipes, but it is surprisingly nice soap after a good cure.

I just don't tell anyone about the chicken fat since so many people gross out about that. Little do they know that it is also a secret ingredient (along with bacon grease) in my GF-DF cornbread that they all rave over.

 

[Arimara]

I should add that I also save fats from cooking, since we make a fair number of roasts and ribs. I strain off the fat into a container, and save it up till I have enough to clean for soap.

I generally know approximately how much is schmaltz, how much is tallow, and how much is lard. That lets me approximate the values for inputting into the soap calculator. But I don't worry too much about it. I still use all my regular additives and other oils, including vinegar, sugar, salt/SL, CO and CaO. I call it my Barnyard Medley recipe. Due to the variable amounts of the different fats, it isn't as consistent as some of my more refined recipes, but it is surprisingly nice soap after a good cure.

I just don't tell anyone about the chicken fat since so many people gross out about that. Little do they know that it is also a secret ingredient (along with bacon grease) in my GF-DF cornbread that they all rave over.

Cornbread is just a triggering topic in general.

 

[CathyB]

I just couldn't let it rest. I went to the University of Idaho for answers:

My question to them: What makes kidney fat “superior?” Is it just the ease of processing, or is there an actual chemical or physical difference in the fat aside from the various connective tissues binding the fat together? I know, from rendering both beef and port, that there is definitely a difference in the physical appearance and texture, but the extent that carries through to the actual molecules is what I’m trying to find out. Not in extreme detail, but in enough detail that I can figure out how it would impact soap qualities.


The response:

Hi Cathy,

Great question! I would agree that leaf fat and kidney fat will be better for making traditional bar soap than subcutaneous fat. Those internal fats have higher quantities of saturated fats, meaning the fatty acids that make it up are straight and stack well in a molecular form. That gives them more substance and will make a more solid bar of soap. Beef kidney fat will be some of the more saturated fat, then pork leaf fat, then beef subcutaneous, then pork subcutaneous. As for the individual fatty acids I’m not sure what the makeup is off the top of my head, but the visceral or internal fats will always be more saturated and therefore more firm. Probably the reason that non animal based soaps often use palm oil due to it’s naturally high saturation content and firmness.


Phil

Go Beef!

Phil Bass, Ph.D.
Assistant Professor, Meat Scientist
Animal and Veterinary Science
University of Idaho

 

[SPowers]

What an interesting thread! I'm not the least scientific so I won't wander into that arena however I have a couple of questions.... why do they call if 'leaf' fat? And secondly, just today when I was working with lard for a soap batch, I very briefly - almost unconsciously wondered about bacon fat. How is that 'cleaned' for use in soap making?

 

[AliOop]

@CathyB that is AWESOME information - thank you!! The only thing I would say is that I'm not sure the solidity of the soap is the only factor that goes into making leaf fat better (or not) than non-leaf. But it is good to know the hardness benefits of leaf over non-leaf. Yay, I love science!

@SPowers yes, you can clean bacon fat for soap-making. If you put it in the search bar above, you'll find a few threads. It's basically the same as cleaning any rendered fat: melt it, clean it (usually water + salt or bicarb) and then strain it. The difference with bacon fat is the strong aroma, and sometimes the darker color that won't come all the way out, even with multiple cleanings. Plus, I hoard my bacon fat for making dishes that need that smoky bacon-y flavor, including scrambled eggs, cornbread, refried beans, and more. There's never enough for all those cooking needs, so in my house, bacon fat goes into food, and rendered lard goes into soap.

 

[SPowers]

I hear ya... I love bacon and cook with bacon fat a lot! I doubt I will do it but I'm interested in the process. Thanks for the response.

 

[AliOop]

Found this great article about leaf lard. Although it is addressed to bakers, I found most interesting the part about the recommended slow cooling to encourage larger crystals. Whether we want larger crystals in soap-making is not clear to me, but perhaps someone with more science background than I can answer that. Here's the excerpt, followed by the source link:

Lard has larger fat crystals than butter. From what I could tell from the research, this isn’t always strictly true. And this is important for butchers to know too. It seems that the size of the fat crystals correlates directly with the speed and intensity of cooling after rendering. FASCINATIN! SO, if you cool your rendered lard more slowly and over more time, you’ll allow larger crystals to develop. Large crystals of fat are good because, as with the higher melting point thing, the crystals take longer to melt in the oven, and create bigger pockets and, therefore, more flake.

Wow, I have to say, I’ll never cool my rendered lard the same way again. But seriously, though, it’s nice to know why things work they way they do. One important note to end with: it appears to me, from all the research I did, that many of these characteristics also apply to regular lard, and regular pork fat. The difference is that leaf lard has the more delicate flavor that bakers prefer for sweet pies. Also, if I can form one hypothesis for us all to think on, I also know that leaf fat renders faster and more easily than normal pork fat and that, perhaps, this interrupts the fat structure less, leading to those desirable big fat crystals. If you can’t find leaf fat to render or leaf lard to use, try regular lard from a good butcher. As long as it’s rendered slowly, it should have a mellow enough flavor. Remember to COOL IT SLOWLY!

https://bavettemeat.com/our-blog/20...n rendered (or,cooked down) becomes leaf lard.