Friday, July 3, 2015

Hitchhiker's guide to fats



My original plans were to post more articles on general reccomentations but I have seen, both in the comments on the blog and from people I directly met, that fats is a confusing topic. The reader is King! I will change my plans and today I will write about fats, how to choose them and how to use them.

Good fats and bad fats

This time it is a matter of black and white: there are indeed good fats and bad fats. Where do bad fats come from? And where do we find them?

Good fats Bad fats
Saturated fats Hydrogenated fats
Monounsaturated fats Trans fats
Polyunsaturated fats Margarines
Good fats gone rancid

Hydrogenated fats, trans-fats and margarines are the result of a deliberate industrial process whose objective is to create a fat that is solid at room temperature (butter-like texture) starting from a liquid vegetable oil.

We can also read it in this way: people want something creamy to spread on their crackers but butter has a short shelf life, let's invent something so toxic that even moulds or bacteria won't eat.

Still not convinced? I don't know whether the following picture is real or fake, I haven't performed the experiment myself (but one day I will). If it turns out to be true, it is quite enlightening:


Attention: the unhealthy trans fatty acids are those obtained through industrial processes and do not exist in nature: our body doesn't recognise them as food. There are natural forms of TFA that are beneficial such as the Conjugated Linoleic Acid (CLA), also found in butter from grass-fed cows. I'll speak about them when I'll debunk the myth that butter is bad for you.

Rancid fats are the product of the involontary deterioration of good fats, either by the action of bacteria and moulds, oxidation, exposure to light or to heat.

Bacteria and moulds are a matter of hygene and proper food conservation. Same for oxidation: exposure to oxigen is likely to promote the degeneration of a lot of food.

Exposure to light is an interesting one: ever wondered why good quality oils are sold in dark bottles? That's correct: so that maintain their status of good quality oils. Light can alter the chemical structure of some delicate oils, this is especially true for those composed in prevalence by monounsaturated fatty acids (ex. olive) and polyunsaturated (ex. flaxseed, canola, soy, corn, safflower, ...).

Exposure to heat: cooking with fats

Cooking deserves a special section.

Polyunsaturated fats are by far the most delicate fatty acids that can be found in an oil. They get rancid with light alone, why should they maintain their properties if you use them for baking of frying? The following oils should never be used for cooking, however they do a perfect dressing on salads or poured over steamed vegetables, or an already cooked steak or fish:
  • flaxseed oil
  • sesame seed oil (my favourite, on smoked salmon...)
  • blackcurrant oil
  • walnut oil
  • hazelnut oil
  • argan oil

Monounsaturated fats are "ok" for baking and sauté. Although they can be altered with heat, they tend to maintain their healthy properties longer than PUFAs.
The following oils can be used both as salad dressing and occasionally for cooking:
  • oil of olive
  • avocado oil
  • macadamia oil
Walnut oil, although it contains monounsaturated fats and is usually considered as a source of MUFAs, contains plenty of polyunsaturates as well (63%). It makes a good salad dressing anyway.

Saturated fats are the preferred choice for cooking. Their tolerance to high temperatures make them the perfect fats for baking, sauté and even deep frying. My favourites are:
  • coconut oil
  • red palm oil
  • butter / ghee (clarified butter)
  • cocoa butter (also called theobroma oil)
  • rendered fat from pork, beef, goose or duck

A short note on fish

Fish is a well know source of ω-3 polyunsaturated fatty acids. One of the biggest insult you can do to fish is overcooking of deep frying it. Ideally, it should be eaten raw (sashimi), smoked or marinated (for example 24 hours in lemon juice).

The technique of cooking fish has a great impact on the health benefits that come from eating it, you can turn a healthy food into an unhealthy one in a matter in minutes. Food for thought: what do Japanese centenaries eat? Fried fish... or sushi?

Smoke point, it's just half of the story

So far so good! Polyunsaturated fats are more prone to deterioration in the cooking process than monounsaturated, while saturated are the perfect type of fat for cooking. And this is biochemistry, not marketing.
Unfortunately this is not what we have been told. Still today (and I fear this will be for many years to come) there is a widespread opinion that The-One parameter to choose an oil/fat for cooking is the smoke point temperature.
The table below lists some fats and oil commonly used on cooking, ordered by smoke point temperature, I took the liberty to add an extra column with the percentage of polyunsaturated fats contained in each:

Fat/Oil Smoke point SFA MUFA PUFA
Avocado oil270°C / 520°F11.6%70.6%13.5%
Safflower oil266°C / 510°F6.2%74.6%14.3%
Ghee252°C / 485°F51.4%21.0%3.0%
Canola oil246°C / 475°F7.4%63.3%28.1%
Soybean oil238°C / 460°F15.3%21.7%58.2%
Sunflower oil232°C / 450°F9.0%57.3%29.0%
Corn oil232°C / 450°F12.9%27.6%54.7%
Peanut oil230°C / 450°F16.9%46.2%32.0%
Grapeseed oil216°C / 420°F9.6%16.1%69.9%
Cottonseed oil216°C / 420°F25.9%17.8%51.9%
Tallow (beef)215°C / 420°F49.8%41.8%4.0%
Extra virgin olive oil207°C / 405°F13.8%73.0%10.5%
Cocoa Butter205°C / 400°F59.7%32.9%3.0%
Coconut oil (extra virgin)204°C / 400°F86.5%5.8%1.8%
Lard (meat drippings)192°C / 390°F44.8%41.8%7.6%
Hemp165°C / 330°F9%11%80%
Butter149°C / 300°F51%21%3%


I empowered you with a new piece of information: polyunsaturated fats become rancid and form toxic byproducts when heated. The table above should now speak by itself, maybe our grandmothers were right: lightly frying your breakfast eggs in butter was not a bad idea after all. Ghee is an even better one.

Let's get pragmatic: real life examples

So far the theory. Unless you are a convinced foodie and cook everything from scratch, you may occasionally or even regularly buy prepared food. There is nothing wrong about it and for people who have little time to cook this is sometimes the only solution. But making the right choice is fundamental.

Trans fats have been banned in some countries and on their way to be banned in others, the evidence against them was too strong. This is a good thing, however make always sure they are not mentioned in the label. When in doubt, buy something else. Trans fats are really bad for you: don't forget that fats become cells membranes and hormones, you deserve to be made of good building blocks.

Hydrogenated oils are still widely used, check for them in the label, sometimes the producer is honest enough to mention them. If the label just reads vegetable oil you can be sure they used the cheapest and most degradable oil possible, if it had been oil of olive or extra virgin coconut oil they would have been proud to add them to the list of ingredients.

Food preparations which are cooked and mention sunflower oil, canola oil or soy oil in their labels, probably contain fatty acids that, although healthy in the beginning, are unhealthy now.

Peanut oil, despite its desirable smoke point, is not suitable for frying or deep frying, as it is usually recommended.

Flaxseed oil (an excellent vegetal source of ω-3 fatty acids) is very unstable both at temperatures and to light exposure. The same for canola oil: not only shouldn't they be used for cooking (as the marketing suggest...) they should be stored in a cold place. All nuts oils (walnut, hazelnut, almond, etc) share the same issue. When choosing oils that are made mostly by mono/poly unsaturated fats, look for the cold pressed ones and preferably in dark bottles.

Sesame seeds are probably the most tasty spice I have in my cooking arsenal. A very bad and widespread practice however is to roast them. While it is true that their taste improves adding some bitter torrefacto notes, the impact on the delicate PUFAs is disastrous. Opt for the raw ones, again: you deserve good quality building blocks.

Nut flours

Before closing, I would like to introduce an idea, which I will continue in another dedicated post. And it is about nut flours, a very popular trend in the gluten-free community. The fatty acids contained in nuts (with the exception of coconut), are mostly monounsaturated and polyunsaturated. Question: does it really make sense to use them for baking? Let me know your thoughts.

Summary

This is not even the tip of the iceberg when it comes to fats, I hope I answered some of your questions.

I am also sure that some new questions raised, so in the end the balance is even: as usual, just let me know in the comments your ideas.

And of course... stay tuned!

2 comments:

  1. I'm not margarine fan, but You wrote: "let's invent something so toxic that even molds or bacteria won't eat". I don't think that the fact that molds or bacteria is not eating something it's bad for us. As example let's take honey. Archaeologists recently founded a honey that's 5500 year old, and still (theoretically) eatable. Sorry it's in polish: http://nowaatlantyda.com/2012/04/19/najstarszy-miodu-dzban/

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    Replies
    1. True, that's because honey itself is very hygroscopic and, just like salt, would instantly dehydrate single-celled organisms (it may also contain traces of propolis which have anti-bacterial and anti-fungal action, this is why honey can be used as a topical solution to promote cicatrization).
      However flyes, ants and cockroaches will eat honey,

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