By Rani Merens, CarbSmart Contributor
Posted 12/7/2001
What Are The Best Fats To Use?
I have recently been asked, "What are the best fats to be using in our low carbohydrate diet?" It's a good question!
I much prefer the lower-tech processing methods that give us lard, tallow, schmaltz, butter, and cold-pressed oils. The very best of all are the fats that naturally occur in the foods we eat on the low carbohydrate diet, those found in meats, nuts, avocados, egg yolks, olives, and so on.
The worst sources of fat are, in my opinion, the hydrogenated vegetable fats: shortening and margarine. The second worst choices would be the solvent-extracted cooking oils.
Let's take a look at how fats are processed.
How Are Animal Fats Processed?
Rendering is essentially melting down fat to extract it from its meat source. Lard is rendered from pork, tallow is rendered from beef, and schmaltz is rendered from chicken. The absolute finest lard there available is called leaf lard, which is rendered from the fat around pig's kidneys.
When I baked pies and pastry back in my pre-low carbohydrate days, I used leaf lard for my pie crusts. The shape of the minute pieces of fat creates air pockets that make the pie crust incredibly flaky and good. Leaf lard is mainly available only to the food industry. Regular lard is rendered from the rest of the pig.
Tallow used to be used widely in frying, but less so now, due to the bad publicity it has gotten over the last 30 years. Remember the very tasty fries that McDonald's used to have? They don't taste nearly as good as they did during the days when they were fried in pure tallow. Most Mexican restaurants that make their own chips fry them in lard, which also results in a better taste than when they are fried in vegetable oil.
If you go to the supermarket and read the labels on canned shortening, you will see the expensive brands like Crisco are pure vegetable shortening, but the inexpensive store brands are almost always tallow or part tallow/part vegetable.
When they factory-render lard and tallow, they cook it down and filter it and generally clean it up, including refining and deodorizing it. But if you buy a block of lard, it really is minimally processed.
How Are Vegetable Fats Processed?
There are two main ways for getting the oil out of plant products. One is literally squeezing it out, which is called cold-pressing. You can find cold-pressed oils at your health food store, the health food aisle in many supermarkets, or on the Internet. Extra-extra virgin olive oil is cold-pressed.
The second method, much more widely used, is called solvent extraction. Solvent extraction is very economical, and therefor more widely used.
Have you ever tasted soybeans? They're not terribly oily, are they! Safflower seeds and sunflower seeds have somewhat more oil, but not by much. Corn is also not a product you would consider high fat, is it? Yet most of our cooking oils are from those four sources, plus olives, which are fairly fatty.
Squeezing an ear of corn or a vat of soybeans won't give you much oil. It requires major processing to extract it. So how do they do that? Let's use soybeans as an example, simply because soybean oil is used extensively as cooking oil, margarine, and in salad dressings.
I consider those oils that are solvent-extracted and/or hydrogenated to be "bad oils." In order to understand why, you need to know how oils are extracted. We already know that lard, tallow, and schmaltz are rendered, and I presume that you know how we get butter: it's basically over-whipping cream until the butterfat coagulates.
First, the soybeans are chopped up and a solvent called hexane is added to it. Hexane is rather like dry cleaning fluid. (If you think about it, we use that fluid to "lift" grease stains out of clothes.) The soybean/solvent mixture is called misella. It's mixed well and then spun in a centrifuge, which removes the liquid (oil plus hexane) from the solids (the protein, carbohydrates, and fiber from the soybeans).
The misella is then heated to cook off the hexane. In addition, they have to bleach, refine, and deodorize the remaining oil. These processes remove the rest of the hexane, the smell, and the impurities. What is left is pretty much plain soybean oil such as Wesson oil in the supermarket.
To make Crisco, they would then hydrogenate it so that it will solidify. To make margarine, they would hydrogenate the oil and add flavorings and color to it. Crisco is basically unflavored, uncolored margarine.
Cold-pressing involves using plain old pressure to extract the oil. However, If they cold-press soybeans, olives, safflower seeds, etc., they can only get part of the oil out. Solvent extraction gets a LOT more yield. Olive oil is generally processed both ways. First they cold-press it for the extra-extra virgin pressing. (Notice the word "virgin." That indicates a first-time pressing.) Whatever is left after the first pressing is solvent-extracted and that becomes "regular" olive oil.
Why Use Solvent-Extraction If Cold-Pressing Results In Healthier Vegetable Oils?
Solvent-extraction is cheaper and results in a lot more product. Cold-pressing is more expensive because it uses up more olives, seeds, nuts, etc., to get the same amount of oil.
Back in the early 1980s, the shortening manufacturer that I worked for was experimenting on a newfangled way of extracting avocado oil using a large centrifuge. The centrifuge separated the pulp/skins/pit from the oil very effectively. The resulting avocado oil came out a deep dark green, but then they had to bleach, refine, and deodorize it. They never did end up marketing it, but it was an interesting process to explore. Perhaps in the future someone will come up with a way to make this process financially feasible. It would be nice to have a healthy alternative to solvent extraction.
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