The Oil from Tiger Nuts and its Extraction Methods

The Oil from Tiger Nuts and its Extraction Methods

One of the most valuable products obtained from tiger nuts is oil. Tiger nut oil (TNO) is rich in plant proteins, polyunsaturated fatty acids, and antioxidants. These components make it an attractive element for both the food and cosmetic industries. But is it really as promising as it seems?

Research shows that tiger nut oil has a similar fatty acid profile to olive, avocado, and hazelnut oils, but it is still much less commonly used in the food industry.

The positive view of its nutritional value, combined with its high stability due to the low content of polyunsaturated fatty acids, tocopherol (vitamin E), and phytosterols (cholesterol), is gaining traction, especially in the current eco-friendly and bio-conscious society. This shift in thinking has led to tiger nut oil being recognized as a nutritionally valuable food that could benefit not only its growers and processors but also its traders.

While most researchers are still deeply studying the components of tiger nut oil, it is also crucial to find effective and environmentally friendly methods for its extraction. Several methods exist to extract TNO efficiently, but each has its pros and cons. This article will explore various oil extraction techniques from tiger nuts and evaluate their potential effectiveness and sustainability.

Types of Tiger Nut Oil Extraction Techniques

In laboratory conditions, tiger nut oil (TNO) is obtained through various methods:

1. Cold Pressing

Cold pressing is one of the oldest yet most popular methods for extracting oils in general. The technique involves using mechanical (physical) force to extract oil from the seeds or tubers of tiger nuts. The cold pressing process generally involves five steps:

• Cleaning and Drying: The tiger nut tubers are first thoroughly cleaned to remove all impurities. Then, they are dried, which reduces moisture content and increases the yield during pressing.

• Grinding/Milling: The dried tubers are ground into fine particles.

• Pressing: The ground tubers are placed into a press, where high pressure is applied to extract the oil. This step can be done either through:

  • Cold pressing, where no heat is used, preserving the oil’s natural nutrients, taste, and color.

  • Hot pressing, where heat is applied to increase oil yield, though this can reduce the oil's quality by removing certain nutrients and altering its taste and color.

• Filtration: The extracted oil still contains solid particles, which are removed through filtration.

• Storage: The filtered oil should be stored in clean, sealed containers in dark places to maintain its quality.

2. Solvent Extraction

In this method, organic solvents, such as hexane, are used to extract the oil. The idea is that the yield of oil will reflect the oil content of the raw material. Typically, the yield of tiger nut oil using hexane ranges from 15.9% to 41.2%, with variations depending on factors like the origin of the tubers, genetic variability, age of the tissue, or variety.

Solvent extraction can achieve more than 95% oil yield. However, this method raises concerns about its sustainability, as it requires petrochemical solvents and poses challenges with strict emissions standards in many regions.

3. Supercritical Carbon Dioxide (SC-CO2) Extraction

Due to the limitations of solvent extraction using hexane, researchers have explored alternatives such as alcohols and supercritical CO2 (SC-CO2), which are non-toxic, non-explosive, and economically advantageous. SC-CO2 has become the preferred option due to its safety and cost-effectiveness.

Though there is limited research on the effectiveness of SC-CO2 for tiger nut oil extraction, one study showed a yield of 26.28%, which is slightly above half of the yield obtained with hexane (41.2%). For comparison, control measurements of SC-CO2 extraction from seabuckthorn and grape seeds yielded 20.8% and 6.9%, respectively, which were comparable to hexane extraction yields (21.5% and 7.5%).

Despite these results, supercritical CO2 extraction is still regarded as an advanced and “eco-friendly” technique for extracting tiger nut oil, but further studies are needed to explore the range of temperatures, time, particle sizes, and moisture content during SC-CO2 extraction.

Conclusion

Mechanical cold pressing is a traditional, eco-friendly method that preserves the nutritional values of the oil. On the other hand, solvent extraction with hexane achieves high oil yields but requires stringent safety measures due to the use of organic solvents. Supercritical CO2 extraction provides an effective and safe alternative, though the costs of equipment and operation can be higher.

Each of these techniques has the potential to produce high-quality tiger nut oil for the market. This expectation is contributing to the growing popularity of tiger nut oil in the food and cosmetic industries. However, as demand for natural and healthy products increases, it is essential to continue research on these and new extraction techniques to ensure the sustainability and quality of TNO.

Source: ResearchGate Article