In our Oil review Part 1 we saw how history played a role in developing refined vegetable oils. We talked about Crisco and how the refining process was developed to make the cheap, unappealing cotton seed oil into a clear, neutral tasting oil. We concluded that unrefined traditional oils retain a lot more antioxidants and nutrients that are beneficial for everyday cooking.
But, you may wonder, is there a way to identify which plant oil ends up typically getting refined? There is also a lot of debate regarding seed oils. But mustard and sesame are ‘seed’ oils that have been used for centuries in India. How different are they from other refined seed oils? Why is palm oil all the rage?
To understand that, let us examine some properties of the commonly available oils in the market. You may be like: “Swetha, I did not sign up for a Chemistry lesson. Just tell me what oil to buy”, but I promise you that this lesson will be brief and very much worth it.
Composition of Oils
Every oil will have some combination of fatty acids grouped into 3 main categories: Saturated, Mono-Unsaturated and Poly Unsaturated fatty acids.
Here’s how most Indian oils stack up in their composition.
Table 1: Approximate fatty acid composition of visible fats (g/100 g).
|Saturated Fat||MUFA (Mono)||PUFA (Poly)|
|Red palm (raw)||50||40||9|
aTransfatty acids (ghee 2%).
What do you notice in the graph above? Do you see all the traditional oils until sesame oil having more concentration of Saturated Fats and Mono-Unsaturated (MUFA) compared to Poly Unsaturated fats (PUFA)?
It is not a co-incidence that all the refined oils come at the bottom with high levels of (i.e. greater than 50%) PUFA. But then you may be thinking – wait a minute, poly-unsaturated – doesn’t that include the famous omega 3, omega 6 fats that are so necessary for us? Yes, but not in their unstable oil form, but rather when they are stable inside their seed form.
Think about it, how do you store flax seed oil (an oil rich in omega-3’s)? In the freezer, right? I mean, a cold pressed flax seed oil has to be handled more preciously than a newborn baby. We can’t afford to let those omega-3’s get rancid. But, how on earth are the large companies selling us oils with high PUFA without them breaking down?? – Answer: Refining.
In the olden days, when you only had mechanically pressed oil + no refining options, people automatically chose oils that would be shelf stable without going rancid in a few days. So, they chose oils with high saturated fat levels (like coconut oil, ghee) or high mono-unsaturated levels (sesame, mustard, olive oil).
Saturated, MUFA, PUFA: why they behave the way they do?
I am going to explain this in fairly simplistic terms. If you are a science expert, you may already know this and you can skip this part.
See the diagram below.
You see, saturated fats are ‘saturated’ with hydrogen. What does that mean? It means other than the end group, all the Carbon atoms are surrounded by Hydrogen atoms (Hydrogen, hydrogen, hydrogen….everywhere hydrogen :)).
If it is mono-unsaturated, then the molecule will have 1 Carbon=Carbon double bond instead of being ‘saturated’ with hydrogen. And if it is poly-unsaturated, then the molecule will have several places with Carbon=Carbon double bond, instead of being ‘saturated’ with hydrogen .
Ok, stay with me, we are getting to the point….Hydrogen being this really tiny, charged atom compared to carbon gets really attracted to Carbon and creates a stronger C-H bond compared to a C=C double bond. This makes the C-H bond harder to break and less likely to react to other chemicals around it when compare to C=C. Another thing, the C-H all lines up so neatly that they all stack up very efficiently so that they end becoming a solid around room temperature.
The mono-unsaturated are one step down. The single Carbon-Carbon double bond creates a slight kink to the chain and thus oils with high MUFA ends up being a liquid at room temperature; although if you freeze them, they may get solid. And yes, while they can become reactive at that single C=C bond, other C’s are still obsessed with hydrogen.
But poly-unsaturated is the most chaotic, unruly child of the bunch. Too many C=C bonds, too many kinks. They refuse to become solid even in the freezer. Presence of oxygen, light, heat etc. upsets and disturbs them and they get very reactive.
There are 2 properties: Melting point and Smoke point that plays a role on the oil properties and their corresponding usage. Let’s look at them in detail.
Melting point: Big win for Saturated fats
All that saturation in Carbon-hydrogen bonding for saturated fats comes in useful. Saturated fats can line up quite compactly and can remain solid until quite high temperatures. Having a high melting point makes the saturated fats very special. Why?
Let’s see in baking: A solid fat at room temperature, saturated fats give pastries their flakiness and their softness. It gives cookies their shape and helps keep them intact. When you eat it, the fat begins to melt in your mouth at body temperature, and that’s what gives a lot of the texture and the taste in those indulgent products that we like. This is the reason why many processed baked goods will have palm oil listed in their ingredients. On the other hand, liquid oil baked goods can be oily to touch or leaves oil residue in mouth.
Indians love to fry in saturated fat. Foods that are fried with high saturated fat will have a more pleasant surface, and the texture has less oil than foods that are fried with unsaturated oil. This is because saturated fats will solidify when cold. This is the reason many restaurants love frying in saturated fats.
Finally, the high melting point of saturated fats is the reason why you see Palm oil in different forms (Palm Stearate, Sodium laureth sulfate, stearic acid, stearate, etc) in your shampoos, moisturizers, hand creams, etc. The ability to give a creamy feel without the greasy, oily feeling.
Let us look at some melting temperatures.
The low freezing point of the PUFA rich oils (cottonseed, flaxseed, sunflower, safflower, etc) help them stay in a liquid form no matter which part of the world they are shipped to – Alaska or the Himalayas – they will remain liquid. Which is actually a desirable property when cooking. You don’t have to wait for the fat to melt to get cooking.
PUFA: Very reactive to heat
Ok, PUFA stays as liquid in a large temperature range. What about the smoke point though? Don’t refined oils have higher smoke points? That’s what everyone keeps harping about, right? – The smoke point!!
|Avocado oil||Refined||270 °C|
|Mustard oil||250 °C|
|Canola oil (Rapeseed)||Refined||204 °C|
|Canola oil (Rapeseed)||Unrefined||107 °C|
|Coconut oil||Refined, dry||204 °C|
|Coconut oil||Unrefined, dry expeller pressed, virgin||177 °C|
|Corn oil||Refined||230–238 °C|
|Corn oil||Unrefined||178 °C|
|Cottonseed oil||Refined||220–230 °C|
|Flaxseed oil||Unrefined||107 °C|
|Olive oil||Refined||199–243 °C|
|Olive oil||Extra virgin, high quality||207 °C|
|Palm oil||Fractionated||235 °C|
|Peanut oil||Refined||232 °C|
|Peanut oil||Unrefined||160 °C|
|Rice bran oil||Refined||232 °C|
|Safflower oil||Unrefined||107 °C|
|Safflower oil||Refined||266 °C|
|Sesame oil||Unrefined||177 °C|
|Soybean oil||234 °C|
|Sunflower oil||Refined||252–254 °C|
|Sunflower oil||Semirefined||232 °C|
|Sunflower oil||Unrefined||107 °C|
Remember, I told you before that PUFA’s are a reactive lot. Do you notice the smoke point of the unrefined versions of sunflower, safflower and canola oils? They are all at 107C, barely above the boiling point of water. They would smoke and probably burn before they hit tadka temperatures.
A hundred years ago, even if we had been able to squeeze the oils out of these PUFA-rich seeds, there is no way we could have used it in our everyday cooking. Only after refining, does the smoke point jump to 250C or above. Without refining, it would have been impossible to use these oils in a large scale.
We can use unrefined MUFAs and Saturated fats for cooking
Our normal tadka range is typically 160 C, which is accommodated by unrefined peanut oil and unrefined sesame oil. For frying, we needed oil that had smoke point of 200C or more. Ghee, unrefined mustard oil and even high quality olive oil seems to be capable of withstanding the heat.
KT Achaya, the famous food historian states that sesame oilseeds can be processed using different techniques. “Very light oil comes from dehusked seeds ground very slowly, to prevent any heating that would add a toasted taste. However, in parts of India, other substances are added to the seeds, which isn’t adulteration since they are accepted local ways to give the oil a certain flavour.” For example, to this day, even in the Idhayam Sesame oil brand palm jaggery is added during the making of sesame oil as per traditional Tamil practices. So, I wonder, if the smoke point varies based on local practices as well.
Nuances regarding oil refining process
Ok, I wanted to wrap up Part 2 of this discussion by discussing nuances. As a writer and health warrior (worrier), I do tend to lean towards nutrition and healthy choices. However, not everything in the world is seen as black and white. I was seeking the help of my uncle, a brilliant man and a retired chemical engineer, whom I respect immensely, to help me better understand the refining process and to ensure that I got the facts right.
He saw my article, mentioned that he liked it. But added “Chemical Engineers look at things made safely at lower costs serving larger population [..] not just the elite.” He is absolutely correct and made a great point. I get it…Many small restaurants or snack vendors businesses may be solely profitable based on the low cost of vegetable oil. I do not deny that.
I also don’t mean to imply that all unrefined oils will be great. There may be contaminations due to unscrupulous vendors or they may go bad earlier than expected due to variations in day-day manufacturing. These factors may be less probable when you buy products that are made at an industrial scale.
While all those arguments stand true; I think if we want to choose an oil that is closer to what nature intended, I feel that is justified. If we want to encourage a cold press oil manufacturer that helps us reach our goals of healthier living, I feel that is also justified. And, hopefully, over time, increase in demand for clean products will ensure that everyone will have access to inexpensive, pure, unrefined oils that are filled with great flavors, smells and nutrition.
Even in the refined oils, refined MUFA rich oils (like our traditionally used oils) like refined sesame or refined peanut oil seems to be better options than going for refined PUFA rich oils like cottonseed, sunflower, safflower, etc.
- Use unrefined versions of sesame, coconut or peanut oils purchased from a trusted retailer (no contamination, no adulterations) for your tadkas, greasing your idli plates, using it for mixing with idli podi and many other such uses for everyday cooking.
- You can use ghee, mustard oil (argemone free) or Extra Virgin Olive oil (EVOO) for 1-time frying. I have given explanations re: EVOO in Part 1 of the series.
- For repeated frying (which you should try and do in a very limited manner), use refined oils. Even in the refined oils, refined saturated or refined MUFA rich oils like refined coconut oil or refined sesame, refined peanut oil seems to be better options than going for refined PUFA rich, unstable oils like cottonseed, sunflower, safflower, etc.
I hope this article was helpful to you. Stay tuned for the last Part 3 of the series where I will discuss individual oils and any red flags to look for when buying them.
If you wish to explore this topic more, watch: