In the present times, India is one of the largest producers of groundnuts in the world and the second largest producer of groundnut ‘peanut’ oil. Most of the groundnuts and its oil are consumed domestically whereas some part is exported. The properties and health benefits of groundnut oil make it a popular cooking oil choice across whole of India.
Traditionally, the states of Gujarat, Andhra Pradesh, Maharashtra, Telengana, Tamil Nadu and Karnataka have been in the forefront of production of peanuts and peanut oils. Production in Andhra Pradesh, Karnataka and Tamil Nadu has grown significantly in past few decades whereas Gujarat and Maharashtra have seen a decline.
In India, peanuts are consumed in different ways. You can have these after roasting or frying. These are used for extraction of their oil and also for making peanut butter.
What makes Peanut Oil good as a Cooking Oil?
Just as mustard oil and desi ghee is used in North India and coconut oil in south India, similarly groundnut oil is used in cooking in traditional Indian style in central and western parts of the country.
The high smoke point of the groundnut oil, at about 450 F or 230°C makes it good for frying and being used as a cooking oil. This is better than most of the other vegetable oils because of its high smoke point. This makes it far more oxidative stable than other oils.
It has a slightly nutty flavour which adds depth to the recipes being cooked in it. Due to a neutral flavour of its own, it does not suppress the flavours and aromas of the items being cooked. The unrefined groundnut oil is more aromatic than the refined one.
Groundnut Oil has low Iodine Value and High Oleate/Linoleate ratio which increases the shelf-life of the oil and prevents occurrence of rancidity for long time.
Nutrient composition of Groundnut Oil
A major part of groundnut oil, as much as 78%, is comprised of unsaturated fatty acids and 17% of saturated fatty acids. Among the unsaturated fatty acids, monounsaturated fatty acids comprise 46% and polyunsaturated fatty acids are 32%. Apart from fatty acids, there is about 15% of Vitamin E. This is summed up below…
|Monounsaturated fatty acids||46%|
|Polyunsaturated fatty acids||32%|
|Saturated fatty acid||17%|
Due to low proportion of saturated fatty acids, it is considered to be good for heart in particular and overall health in general.
The exact fatty acid composition of groundnut oil can vary from one variety to another. However, it has been observed that, in general, the composition is highest of Oleic Acid (about 50%), followed by Linoleic Acid (about 30-35%), Pamitic Acid (about 10%), Stearic Acid (about 3%) and Arachidic Acid (about 2%).
In mature peanuts, the oil is 96% triacylglycerol with the main fatty acids being palmitic, oleic, and linoleic. The percentage of FFAs in peanut oil varies between 0.02 and 0.6%.
Peanut oil is a natural source of trans-free fat, antioxidants, vitamin E, phytosterols, squalene and p-courmaric acid which help in keeping us healthy.
The fatty acid composition of peanut oil varies according to genotype, seed maturity, agro-climatic conditions and location.
Physical and Chemical Properties of Groundnut Oil
Groundnut Oil gets its physical and chemical properties on the basis of its fatty acid composition as is given above. In its physical appearance it is pale yellow with a nutty taste and smell. This is obtained by the processing of its kernel. After refining, the smell of the oil goes away.
Richness in Oleic acid content gives it its oxidative and freezing stability properties.
Aflatoxin, which are largely absent from refined groundnut oil, are considered to be carcinogenic.
What makes peanuts good for health?
Peanuts have been consumed for a long period of time in countries of South America, Africa and Asia. However, it is only now when elaborate studies on peanuts, peanut butter and peanut oil for human health were conducted that its usefulness was proved beyond doubt.
Peanuts, its butter and oil –all three have been found to be useful in preventing inflammation which is believed to be root cause of many chronic diseases.
Oleic acid has been shown to have a positive influence on cardiovascular risk factors, such as lipid profiles, blood pressure, and glucose metabolism.
Potential Health Benefits of Groundnut Oil…
1/5. Groundnut Oil is Anti-Inflammatory
Groundnut oil is anti-inflammatory in nature. Inflammatory C-reactive protein in blood is indicative of chances of cardiovascular diseases. Certain fats, antioxidants, dietary fiber, arginine, and magnesium have been shown to help regulate inflammation. Peanut oil contains resveratrol which performs anti-inflammatory activity. This is achieved by effectively inhibiting lipopolysaccharide (LPS)-induced nitric oxide (NO) production. Resveratrol exerts anti-inflammatory effects in microglia and astrocytes by restricting growth of different pro-inflammatory cytokines and important signaling molecules.
2/5. Peanut Oil is anti-tumour and anti-cancerous
One of the greatest advantages of Groundnuts or groundnut oil is that this is very helpful in anti-cancer activity. It contains certain phyto-chemicals, such as β-sitosterol, campesterol, resveratrol, and sigmasterol, which help in prevention of different types of cancers, such as breast, colon and prostate. Studies conducted on rats have shown that these help in preventing tumors at all stages, whether in beginning or during progression.
Resveratrol prevents formation of free radicals which inhibit formation of tumour. Therefore, it acts as an antimutagen. This compound was found effective as a chemopreventive treatment for pulmonary metastasis of CT 26 cells in rats. Besides the groundnut oil, roasted peanuts and defatted peanut dregs also exhibited antimutagenic and antiproliferative effects at concentration levels of 100mg/ml. The proliferation of leukemia U937 and HL-60 cells was inhibited by 56 and 52% respectively at this level of concentration. A 10 year study on usefulness of consuming peanuts in women also showed that it may help in preventing cancer.
These studies have proven that peanuts, its products and even its by-products can have potential use as chemotherapeutic or chemopreventive agents.
3/5. Groundnut Oil can improve Cardiovascular Health
Groundnut oil has also proven to be extremely helpful in improving cardiovascular health. Studies have shown that people of all age groups, whether males or females, and in different medical conditions who eat peanuts frequently, have a lower risk of heart diseases. Many epidemiological studies conducted over a period of 10 years in past have shown that people who ate nuts, including peanuts, four to five times in a week had a 30-50% reduction in cardiovascular diseases.
This is attributed to the decrease in LDL and total cholesterol levels which is due to low level of saturated fatty acids in peanuts, peanut oil or peanut butter. This reduction did not affect the levels of good cholesterol HDL.
These have shown to reduce development of atherosclerosis in animals even when atherosclerosis-inducing diet is given to the animals. This was because there was retardation in increase of aortic cholesteryl ester.
It shall be noted that the preventive effect of groundnuts or its oil or butter on atherosclerosis did not change with the change in the way it was consumed or the way it is processed (like, raw, roasted, unroasted, with salt or without salt, etc). Consumption of 56 g of peanuts daily for 4 weeks in any form resulted in significant increase in HDL and decrease in LDL, TAG and total cholesterol. This study outlines the fact that irrespective of the type of processing method used, the lipid-lowering effects of groundnuts were not compromised in processing.
4/5. Helps prevent Cognitive Decline (Alzheimer’s Disease)
Vitamin E and Niacin are two nutrients which are helpful in preventing the progress of Alzheimer’s disease. Peanut oil is rich in Vitamin E. Studies conducted on thousands of people of age 65 years or more have shown that niacin and Vitamin E consumed through food slow down the rate of cognitive decline. However, when Vitamin E is given in the form of supplement, it is not able to slow down cognitive decline.
Another bioactive component which is capable of arresting cognitive decline and prevent degeneration of other nerves is resveratrol. Peanuts are rich in this component as well.
5/5. Groundnut ‘Peanut’ Oil is anti diabetic
Peanut oil is also known to lower the high blood sugar levels, especially of Type 2. It shall be noted that the people with Type 2 diabetes do not produce sufficient amount of insulin and it can not be used adequately by body. In studies conducted on rats and animals, it was observed that the presence of oleic acid in peanuts was able to reduce the Type 2 blood sugar levels. Those who were administered with high oleic acid were able to reverse the inhibitory effect of TNF-α on insulin, thereby increasing insulin production in body. Groundnut oil finally reversed the negative effects of inflammatory cytokines observed in obesity and noninsulin dependent diabetes mellitus.
Similarly, in a study on more than 83,000 women conducted by Harvard School of Public Health, it was observed that women who ate peanuts at least 5 times a week reduced Type 2 diabetes by almost 30% compared with those who never ate it. Interestingly, this reduction happened irrespective of the existence of known risk factors of Type 2 diabetes, such as smoking, alcohol use, BMI or family history.
Methods used for extraction of Peanut Oil
The process of extraction of oil from peanuts determines how nutritious the oil will be. There are five methods employed for this purpose…
1/5. Hydraulic Pressing
As name suggests, hydraulic press is used to crush the groundnut and extract oil. It is followed by hot solvent extraction for total extraction.
2/5. Expeller Extraction
In this method friction and pressure within the expeller helps in heating the meal of peanuts which facilitates oil extraction. Till this stage 50% of oil is extracted. Thereafter, hexane is used for extracting remaining oil. Hexane itself if removed at the end of process by evaporation-condensation process.
3/5. Solvent Extraction
In this process, petroleum hydrocarbons or other solvents are used for extraction of oil. This is a more efficient method as compared with other methods.
4/5. Super Critical Fluid Extraction
This has been a late innovation in extraction process which ensures that there is no residual organic chemicals left in oil. Supercritical carbon dioxide and food grade butane are generally used for this purpose.
5/5. Aqueous Enzymatic Oil Extraction
This method is based on the use of enzymes and mechanical methods, without intervention of chemicals, for extracting oils. This makes it an eco-friendly way of extracting oil. In this, the groundnut seeds are first ground finely which are then dispersed in water. Thereafter, centrifugation is done in this dispersed medium to separate oil, solid and aqueous phases. The use of enzymes during this process enhances the recovery of oil by breaking the cell walls.
After the oil is extracted, it is the turn to refine it. The main purpose of the refining process is to remove non triacylglycerol components, including free fatty acids, pigments, glucosides, waxes, non-hydratable phosphoacyl glycerols, sterols, hydrocarbons, and other compounds that inhibit flavour or oxidative stability. Refined oil is then deodorised by heating it under vacuum.