This marks the first of three posts, each one focusing on a different macronutrient class (fat, protein and carbohydrates).
Fat was probably the key nutrient in human evolution. Protein intake in humans is limited by our kidneys ability to handle waste nitrogen. Carbohydrates are not readily digestible without extensive processing (grinding and cooking). During the beginning of the emergence of hominids, our ancient ancestors likely got ahead in the world by learning to hunt or scavenge fat from large herbivorous animals. Animal fat was the original oil well that humans tapped into, triggering an explosion of cultural and genetic changes. Even today hunter-gatherers will abandon kills that are not plump enough. Protein alone is not worth the effort of carrying back to camp.
Animal fat becomes even more important when you consider the capacity to store it for long periods of time once it is properly processed. The saturated fat from animals can be quite easily separated from water and protein, leaving a product that is resistant to microbial degradation. The process of rendering fat was a common habit in pre-industrial kitchens, and it still takes place at animal processing plants today.
Animals were the primary source of fat in the human diet in many places up until the world war period of the early 20th century, after which time production could not keep up with demand from an exploding population. After that point improvements in processing technology, and the invention of chemical preservatives, made it possible to deliver polyunsaturated seed oils like canola, cottonseed, soybean, sunflower and rice bran oils. Olive oil is intermediate in stability since it is mostly monounsaturated, hence why it could be traded on a massive scale since the days of ancient Greece. Palm and coconut oil are mostly saturated, so also have a deeper history.
Before the industrial era polyunsaturated seed oils could be created, but were consumed immediately before they reacted with oxygen and turned rancid. Linseed oil is probably the best example of this chemical reaction- when exposed to the air it turns to varnish, and can spontaneously catch fire if left on a porous rag. Canola and cottonseed oil have additional toxins (erucic acid and gossypol, respectively, with their own health effects). The chemical preservatives used to stabilise polyunsaturated seed oils (like TBHQ) have their own potential health impacts.
Before the world wars incidence of heart disease and cancer were much lower than today. The cause of this is hotly debated, but some researchers point to the shift to polyunsaturated seed oils as a cause. Personally, I decided to phase out the use of seed oils in my kitchen. The first step of the transition was using blocks of beef tallow, now available in our local shops for the same price as butter. Pork lard is also pretty common, but given the concentrate dependent diet of commercial pig production I prefer the predominantly pasture fed option of beef tallow. It takes a little more effort to cut off a slice into the frying pan compared to pouring a liquid oil, but it is not a big deal when you get used to it. Vegetables roasted in tallow turn out a million times better than those in vegetable oil ever did.
I have goats, and process a few spares for the freezer every year. That means I have an opportunity to produce my own tallow during the process. A standard disclaimer- rendering fat involves handling hot oil in an oven, so take all necessary precautions to avoid burns and grease fires. The quality of fat varies a lot between parts of a carcass. The warmest parts of the animals have the fat which is mostly saturated, and therefore more stable when purified. The best deposits are around the kidneys, but smaller amounts occur around the heart and intestines. By contrast fat from under the skin tends to be soft and more unstable in storage (and this better used for soap making if you are inclined).
The rendering process is pretty simple. I merely slice the cooled, solidified fat deposits into slices a bit under 1 cm wide, and put them in a baking tray (with enough high sides- don’t overload them or moving them when they are full of hot oil is a major hazard). Carefully trim every trace of meat from the fat as you go since it will taint the final rendered fat. Particularly watch out for the lymph nodes hiding inside the kidney fat bodies. I then heat the trays to 160 C, and monitor. Once a few millimetres of liquid fat has separated, I carefully tip the trays to pour the hot oil through a paper filter. Wipe any drips under the tray to reduce the chance of oil fires in your oven. Even after filtering the hot oil will often develop a slimy scum layer. Skim this off carefully with a spoon. I usually pour about three to five times for each tray, until you are left with a crisp golden husk of the original tissue. The first pouring of oil will normally be cleaner, with the later pours developing a slightly meaty aroma (which doesn’t matter if you are mostly using the final product for savoury dishes).
The cooled product should have a firm, non-sticky surface. If any soft fat or gooey residue remains it is more likely to attract moisture and develop mould. I slice the rendered fat into blocks and freeze them, but intend to start experimenting with how to store it at room temperature during our short winter months. We mostly rely on our flow of dairy products to supply saturated fat during the warmer months, relying on periodic goat culls and rendered fat during the winter when the goats are dried off. A brief gap usually happens in mid-autumn, conveniently filled by macadamia nut season (though my seed grown orchards will need a bit longer to start producing).
Rendering your own fat is just another long lost skill, simple when you know how to do it, but liable to a hundred little mistakes when you are first learning. Living on a meagre diet of tubers in the difficult future ahead becomes a lot more pleasant to imagine when we can turn them into the ultimate comfort food, crispy skinned roast vegetables, thanks to a dollop of luscious lipids.