Indian cooking differs from the western cooking. Oils form an integral part of Indian culinary style, and which is commonly subjected to very high temperatures. During deep frying the temperature of oil can go above 170 °C.
But at such high temperature, certain oils such as refined oils with high PUFA are subjected to degrade into toxic components like free radicals, transfats, malondialdehyde (MDA), etc. These toxins are potentially mutagenic and atherogenic.
Properties of oil can be further deteriorated by repeated frying. It is preferable to avoid refined oils and use cold-pressed or extra virgin oils. So, Oils high in saturated fats like ghee/coconut are ideal for deep-frying, as they are more stable.
Palm and soyabean oil account for almost half of total edible oil consumption in India followed by mustard and groundnut oil. However, choice of cooking oil often depends upon the abundance of supply of raw ingredient. While Mustard/ rapeseed oil is chiefly used in the northern and eastern part of India, South Indian people use coconut oil while in the western parts, grow groundnut is chiefly used. As awareness of diseases and health is increasing, a brigade of different oils is being introduced into the market now and then. Groundnut, mustard/rapeseed, sesame, safflower, linseed, nigerseed/castor are the major traditionally cultivated oil seeds. Soybean, sunflower, rice bran oil and cottonseed oil have gained popularity in recent years.
Which oil is to be used? A head-banging question! Every oil has its own pros and cons. Sometimes, the usage depends upon the ease of availability. But the truth is these oils are mainly fats, notorious to cause Heart diseases. Let’s take a review of the properties of all available oils. Decide for yourself. Let’s start with the basics first.
Why do we need fat in our diet?
- Fats are energy dense. Fatty acids provide is about 9 kcal per gram energy in comparison with about 4 kcal per gram for carbohydrates and proteins (almost double).
- Fat supplies per unit weight more than twice the energy furnished either by carbohydrate or protein. Dietary fats are stored in adipose tissue, which is a ready source of energy when food is unavailable.
- Fat provides palatability to diet
- Fats are precursors of biologically active compounds of the body
- Presence of fat is essential for the absorption of fat-soluble vitamins
like A, D, E.
- Some fats called Essential fatty acids (EFAs) have a vitamin-like function in the body
- Fat is an essential substrate for the synthesis of hormones: steroid hormones, testosterone, oestrogen and progesterone
- Fats form an important constituent of body fluids and cell membranes
- Subcutaneous layer of fat insulates the body.
- Fat pads at buttocks and palms protect the underlying bones
Oils are like any other organic material is made up of three elements:-
These elements combine together to form chains known as fatty acids. Three of these chains then join together to form a molecule known as a triglyceride, the basis of all oils and fats. Oils are fat liquid at room temperature. Fat is a term used in the context of fat solid at room temperature.
Edible oils have several fatty acids, which can be grouped into three classes:
1. Saturated fatty acids (SFA)
- Saturated Fats is generally higher in those fats which are solid at ambient temperatures.
- Naturally hard
- Extremely stable
- Have a long shelf life.
- SFAs have 3 groups, short-chain,C2–C6), medium- (C8–C12) and long- (C14–C24) chain fatty acids).
Safety of SFAs
Short and medium-chain SFA are not harmful, as they do not affect the serum lipids. Like Coconut oil is made up of about 90% saturated fats and 9% unsaturated fats. However, over 50% of the fats in coconut oil are medium chain fatty acids, such as lauric acid (12:0). Medium chain saturated fatty acids allows them to be directly absorbed from the intestine and sent straight to the liver to be rapidly used for energy production and thus MCFAs do not participate in the biosynthesis and transport of cholesterol, attributable to the cardioprotective role of coconut oil.
The dietary sources of these fats include animal fats: fat in milk, cream, butter, cheese, meat, ghee, animal tallow and among vegetarian sources coconut, palm, and palm kernel oils. Baked goods such as cakes, biscuits and pastries can also be high in saturated fat.
Saturated fat is notorious components of oils responsible for increase blood cholesterol levels, one of the major factors in heart disease.
It is advisable to reduce average total fat intakes to 30–35% dietary energy and to lower saturated fat intakes to approximately 10% of dietary energy. Trans fatty acids consumption should be less than 1% of the total daily energy intake (WHO, 2003).
2. Unsaturated fatty acids
There are three types of unsaturated fatty acids:
– Monounsaturated (MUFA)
“Mono” means one. So, monounsaturated Fatty acids have only one double bond in their chemical make-up.
- MUFAs are relatively stable to oxidation and the development of rancidity and are now considered, in nutritional terms, as being the best type of fat to eat.
Dietary sources of MUFA are
- Olive oil
- Groundnut oil
- Rice bran oil
- Mustard oil/ rapeseed oil
- Canola oil
- Nuts like almonds, peanuts
- Fruits like olives and avocados
– Polyunsaturated (PUFA)
- Linolenic (LC or n6)
- Alpha-linolenic (ALNA or n3) acid
Poly means multiple. Polyunsaturated fatty acids contain two or more double bonds in their chemical make-up. They are the least stable fatty acids to oxidation and as such are best used in cold applications.
The human body can produce all but two of the fatty acids it requires, known as omega fatty acids. Linoleic acid (LA, C18:2n-6) and α-linolenic acid (ALA, C18:3n-3).
The main dietary sources of LA include plant oils such as sunflower, safflower, soya bean, corn oils, cottonseed oil, cereals, animal fat, and wholegrain bread. Rich dietary sources of ALA include green leafy vegetables, Canola oil, flaxseed, linseed and rapeseed oils.
Benefits of unsaturated Fatty Acids
- MUFAs can lower serum triglyceride levels and improve
disorders of glucose metabolism.
- PUFAs are essential components of cell membranes and nerve tissues.
- PUFAs particularly n-3 increases insulin sensitivity, increase peripheral glucose utilization and decrease adiposity.
- n-3 PUFA of animal origin- fish oils and microalgae have greater antiatherogenic, antithrombotic and anti-inflammatory effects than alpha-linolenic (n-3) acid of plant origin.
- High intake of n-6 PUFA in the diet decrease plasma cholesterol as well as high-density lipoprotein (HDL, Good cholesterol ) cholesterol level.
- So, an appropriate balance of n-6 and n-3 fatty acids is essential in the diet for the optimum functioning of vascular, immune, nervous and renal systems and for early human development.
3. Trans fatty acids (TFA))
Trans fatty acids typically come from two sources, hydrogenated vegetable oils (vanaspati ghee) and animal fats.
High intake of TFA is also associated with increased CHD events and mortality and also possibly other chronic diseases like Alzheimer’s disease, cancer, diabetes, obesity, inflammation, depression, etc.
How Trans fatty acid produced Hydrogenation
Hydrogenation is the process by which hydrogen is added directly to points of unsaturation in the fatty acids. Trans fats are firmed only after partial hydrogenation. Trans fats have more structural stability and provide the required texture to foods.
Hydrogenation of fats :
(1) convert liquid oils to the semi-solid form for greater utility in certain food uses and
(2) increase the oxidative and thermal
stability of the fat or oil.
Where are trans fats found?
- Partially hydrogenated vegetable oils (vanaspati), shortenings, stick (or hard) margarine.
- Cookies, crackers, snack foods, fried foods (including fried fast food), doughnuts, pastries, baked goods- cakes, cookies, pastries, puff, toast, Khari, etc. Readymade mithais and ready to eat snacks like samosa, etc. and other processed foods made with or fried in partially hydrogenated oils.
- Some trans fat is found naturally in small amounts in various meat (beef and lamb) and dairy products.
- In India, trans fats are available as Vanaspati and Dalda.
What TFAs do to our body
– increase LDL cholesterol levels
– Lower HDL cholesterol
– Increases lipoprotein levels, associated with risk of CHD.
– Trans fat raises plasma triglyceride levels, another factor associated with an increased risk of CHD.
– TFAs can adversely affect Essential fatty acids metabolism and prostaglandin balance, promote clot formation
– Promote insulin resistance in humans.
Health risks associated with trans fats
1. Heart Diseases
Trans fats have adverse effects on blood lipid levels–increasing LDL (“bad”) cholesterol while decreasing HDL (“good”) cholesterol. This combined effect on the ratio of LDL to HDL cholesterol is double that of saturated fatty acids.
TFAs increase the ratio of plasma low-density-lipoprotein to high- density-lipoprotein cholesterol and adversely influence the risk of coronary heart disease.
A positive association was found between trans fatty acid intake and the incidence of cancer of the breast and large intestine.
TFAs can increase insulin resistance worsening glucose metabolism.
4. Effect on Fetus
TFAs can be transferred to the fetus, studies have found, the same levels in the blood of newborn infants as in that of mothers. Both the fetus and the breastfed baby are consequently exposed to TFAs corresponding to the
mother’s intake. Dietary trans fatty acids can in part compete with essential polyunsaturated fatty acids in the body which are very essential for both growth and the development of vision and the
brain early in life.
Studies have found a positive association between the intake of trans fatty acids and these asthma, allergic cold and asthmatic eczema in children aged 13-14 years.
Trans fat can increase weight gain and abdominal fat, despite a similar caloric intake.
On the basis of WHO recommendations, there are basically three parameters to adjudge any oil as healthy oil –
1. Ratio of saturated/ monounsaturated/ polyunsaturated fatty acid: 0.8 to 1
As per recommendation, the preferred cooking medium is monounsaturated fat. As about 15% of visible fat should come from MUFA. Therefore, recommended cooking oils would be groundnut
oil, rice bran oil, canola oil, mustard oil, etc. None of the above cooking media gives a desirable fatty acid profile as most the fats which contain MUFA do not contain appropriate ratios of omega-3
fatty acids. For this reason, it is better to rotate oils while using and also use nuts which contains these fatty acids.
American Heart Association recommends a balance of SFAs, MUFAs and PUFAs in the ratio of 1:1:1 and preferably with even a less than 1 ratio of polyunsaturate.
2. The ratio of essential fatty acids (Omega6/Omega3): 5:1 to 10: 1
Increased omega-6/omega-3 ratio contributes to the prevalence of atherosclerosis, obesity, and diabetes. Regular consumption of diets rich in omega-3 PUFAs has been associated with low incidence of these diseases. So, a proper balance of these two essential fatty acids is mandatory.
Olive oil does not have the ideal N6 N3 ratio and may not be suitable for deep frying.
Mustard oil is considered healthy edible oil because it is low in SFA, high in MUFA and PUFA, especially alpha-linolenic acid, and a good n6:n3 ratio (6:5).
3. Presence of natural antioxidants
Antioxidants present in several oils (like tocotrienols, tocopherols, oryzanol, and phytosterols) have favourable effects on lipids and oxidative stress and can prevent heart disease.
Apart from the above properties, cooking oil should have a high smoke point.
- The smoke point is the temperature at which a fat or oil produces a continuous wisp of smoke and is a useful indicator of an oil or fat’s suitability for frying. Beyond a smoke point, oil starts to burn or begins to smoke producing harmful chemicals.
- Basically, oils with high smoking point do not break down at high temperature. Not only they are safe but can be reused for frying, deep frying.
- Fats with a smoke point below 200 °C are not suitable for deep frying.
- Products like extra virgin olive oil contain a great deal of non-fat components, like the anti-oxidants, so it tends to have a lower smoke point. Very refined oils have a higher smoking point.
- Vegetable oil has a high smoke point than oil of animal origin. Refined oils have a higher smoke point than unrefined oils.
- Every time the oil is reheated, smoke point dips. Avoid to use used oil. Reheating oils can be dangerous.
- Oils with high smoking point-Sunflower, Safflower, Soybean, Rice Bran, Peanut, Sesame, Mustard and Canola oil.
- On the other hand oils with a low smoke point like olive oil should be used for sautéing, steaming, stewing and as a salad dressing.