• Indicies

The rate of acid level measures the quantity of free fatty acids present in the virgin oil. Therefore, the quality of the oil is reduced as the acidity increases. The EU established a maximum acidic limit of 0.8 for the extra virgin oils.

The rate of peroxides is an indicator for the level of oxidation of the oil. The virgin oils must show a rate of peroxides equal or less than 20. The tigernut oil, due to its high content in natural antioxidants such as tocopherols (vitamin E) and poliphenols, shows a good antioxidant capacity.

Vitamin E is a liposoluble vitamin essential for the organism which is shown in different ways called tocopherols and tocotrienols. The most effective way is the tocopherol, which acts not only as a natural antioxidant, but also as a fatty acid protector; it reacts with the free soluble radicals in lipids in the cellular membrane.

Due to this, vitamin E acts as a protector against aging getting rid of free radicals that cause degeneration in the skin and takes part in preventing the delaying of eye problems, such as cataracts. It’s also beneficial in preventing psychological aging such as loosing memory and against the apparition of anemia.

This vitamin cannot be destroyed by the direct action of acids or alkaline, but it can be affected by the polyunsaturated fats and the constant exposure to UV rays, high temperatures and oxygen.

The mean range of vitamin E in olive oils can oscillate between 90 and 175 mg/kg while in tiger nut oil it is over 350 mg/kg.

The rate of K232 shows the initial oxidation of the oil at a wavelength of 232 nm in the UV spectrum. The maximum limit for the extra virgin oil is 205 and for virgin oil, 206.

The rate of K270 means an advanced level of oxidation, thus as the measurement of oxidation moves forward there are other components obtained that absorb UV light with a different wavelength (270 nm). Its value is generally lower than 0.20 for the extra virgin oil and 0.25 for the virgin oil.

At these rates, components of complex oxidation (non peroxides) can be observed, originated by an early recollection, a bad preservation, a bad extraction or a development of biological processes. This is said to be an unspecific method but it creates an idea of freshness of the oil, hence the greater the coefficient the less antioxidant capacity.

Delta K (ΔK) is used fundamentally as a purity test for the oil and to detect possible mixtures with refined oils, since in the refining process of the oil, specific components that absorb a 270nm wavelength are formed, but also shows some peaks of absorption that do not exist when the oil is virgin. The formula to calculate this is:

Delta K (ΔK): K270 – ½ (K266 + K274)

(For the virgin oils, the K270 is approximately equal to the sum of K266 and K274 divided by 2, so ΔK = 0.)

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