Concentration of Antinutrients and Chemical Properties of Tiger Nut Oil
Tiger nut oil (TNO), also known as chufa oil, is a nutritious plant oil derived from the tubers of the Cyperus esculentus plant. This oil has high nutritional value, yet it is less commonly used in the food industry compared to oils such as olive or peanut oil.
Its composition is rich in a variety of essential fatty acids, vitamins, and antioxidants that are beneficial to health. However, like many other foods, it also contains certain antinutrients, or "anti-nutrients."
Antinutrients
Antinutrients are substances naturally present in some foods that have the potential to reduce the absorption of important nutrients in the human body. While they are often considered undesirable, they can also have beneficial effects.
Common antinutrients include phytic acid, oxalates, tannins, lectins, and saponins. Phytic acid, for example, can bind minerals like iron, zinc, and calcium, reducing their absorption in the digestive tract.
On the other hand, saponins and tannins have antioxidant and anti-inflammatory properties, which may contribute to overall health.
It is important to note that proper food processing—such as fermentation, cooking, or, in the case of tiger nuts, soaking—can significantly reduce their content and improve nutrient availability. Understanding the role of antinutrients and how to process them properly is key to fully utilizing the nutritional potential of foods like tiger nuts.
Antinutrients in Tiger Nuts
In addition to the mentioned substances, tiger nuts contain other compounds that researchers suggest could act as secondary antinutrients. One such substance is amygdalin.
Amygdalin
Amygdalin is a naturally occurring cyanogenic glycoside found in some plants and their seeds. Although its antinutritional effects are not particularly significant in tiger nuts, its composition warranted research. Amygdalin breaks down into hydrogen cyanide (a colorless, highly toxic liquid), benzaldehyde (a liquid with a distinct almond-like smell), and glucose. These compounds indicate a potential risk of toxicity, though this is only a concern at higher doses.
The presence of amygdalin in tiger nuts suggests the presence of cyanogenic compounds, supporting the claim that raw tubers contain cyanogenic glycosides.
However, based on experiments conducted on mice, acute toxicity of tiger nut extract at the given concentrations was fully dismissed. Moreover, another study not only confirms the absence of toxicity but also suggests the anti-infective properties of tiger nut oil.
Thus, while amygdalin may have potential antinutritional effects by binding to enzymes and inhibiting their function, its presence and health implications in tiger nuts appear to be less significant.
Chemical Properties of Tiger Nut Oil
Tiger nuts contain a high amount of oil, which is rich in monounsaturated fatty acids, similar to olive oil. Its composition includes oils with high oleic acid content, contributing to its stability and nutritional benefits.
Acid Value (AV)
Studies indicate that the concentration of free fatty acids (FFA) in the oil is measured by its acid value (AV), which is given in milligrams of potassium hydroxide (KOH) required to neutralize the fatty acids in 1 gram of oil (mg KOH/g oil). Acceptable AV values for plant oils should be less than four.
Higher AV values indicate reduced quality of the oil. Most of the evaluated AV values for tiger nut oil (TNO) are low, ranging from 0.03 to 1.38, suggesting good quality. However, tubers grown in the USA showed high AV values of 15.7, pointing to poor handling and processing.
Identification of Secondary Oxidation Products
p-Anisidine Value (p-AV)
The p-anisidine value (p-AV) is used to identify secondary oxidation products in oils and provides information about non-volatile carbonyls. Non-volatile carbonyls are stable organic compounds that remain in oils after processing. In the food industry, they are important because they can indicate oxidative changes that reduce the quality of the oil and affect its taste and aroma.
Therefore, it is stated that high-quality oils should have p-AV values lower than two. In the only known p-AV test for tiger nut oil (TNO), a negative value was reported, but this was considered incorrect due to the presence of water in the samples and reagents. Negative values are not realistic, so further detailed studies are needed to determine the actual p-AV value for TNO.
TBA Test
In addition to p-AV tests, the Thiobarbituric Acid (TBA) test is commonly used to measure secondary oxidation products. It detects the presence of malondialdehyde and related aldehydes, which are characterized by sharp, often unpleasant odors. By measuring TBA values, it is possible to assess not only the oxidative stability of tiger nut oil but also its freshness, with lower TBA results indicating less oxidation and better quality.
Studies involving deep frying revealed that tiger nut oil mixtures have better stability (lower changes in TBA values) compared to some other oils. This is attributed to its composition, which includes natural antioxidants and a favorable fatty acid profile.
Roasted Tiger Nut Oil
The taste of roasted tiger nut oil (RTNO) has also been studied. It has been found that roasting reduces the antinutrient content in the tubers, and the oil’s flavor is described as chocolate-like to caramel, with a subtle coffee undertone. This makes RTNO a natural source of aromatic compounds and flavors, potentially helping to restore lost aroma in food.
Conclusion
In conclusion, tiger nuts are rich in plant-based proteins, polyunsaturated fatty acids, and antioxidant vitamins that are beneficial to human health. However, they also contain some antinutrients, such as amygdalin, which can form cyanogenic compounds when raw. The chemical properties of tiger nuts, including low levels of polyunsaturated fatty acids and high stability, make it a valuable oil for various industrial applications. However, to fully understand and utilize the potential of TNO, continued research and testing are necessary.
Source: ResearchGate