Frontier Application | Application of Low-Field Nuclear Magnetic Resonance (LF-NMR) in Flaxseed Oil Encapsulation Analysis

Application Background

 

Flaxseed oil has become one of the fastest-growing edible oils in recent years. Extracted from flax seeds, it is naturally rich in unsaturated fatty acids and numerous nutrients, making it highly sought after in the health food market.

Beyond its nutritional value, flaxseed oil contains bioactive compounds such as alpha-linolenic acid (ALA), which is a precursor for essential long-chain omega-3 fatty acids EPA and DHA in the human body[1]. Its benefits include supporting vision, enhancing cognitive function, reducing allergic responses, inhibiting cancer occurrence and metastasis, promoting insulin secretion, extending blood-sugar control, and mitigating complications. As such, flaxseed oil is considered a functional food with increasing consumer appeal and a promising market outlook[2].

Interestingly, studies show that flaxseed oil can promote the growth of Lactobacillus acidophilus and enhance its tolerance. This in vitro test simulates survival in a medium containing bile salts, mimicking the human small intestine, which is a key criterion for probiotics to be incorporated into foods and beverages.

Regular consumption of flaxseed oil, whether in its fresh form or incorporated into foods such as bread, biscuits, cakes, and dairy products, provides health benefits. For incorporation into other products, micro- or nano-encapsulation can be employed to preserve the bioactivity of the oil[3].

Nano or Micro Encapsulation

 

Nano- or micro-encapsulation involves enclosing bioactive compounds within capsules of microscopic or nanoscopic size to protect them from degradation due to heat, oxygen, light, pH changes, or unwanted interactions with other substances. Typically, a solution containing polymers and active ingredients is emulsified in water, then organic solvents are removed via stirring to form nanoparticles.

The underlying principle relies on introducing an organic phase into the aqueous phase, where diffusion effects occur, and polymers naturally collapse to form micro- or nanoparticles that encapsulate the active ingredients.

To analyse the materials or substances after extraction and encapsulation, nuclear magnetic resonance (NMR) can be applied. NMR spectroscopy is commonly used to characterise both solid and liquid samples. Recent advances allow for 1D, 2D, and multi-dimensional experiments, providing detailed information on structure, composition, purity, and molecular dynamics[4].

Application Overview

 

This case study demonstrates the extraction, characterisation, and micro-encapsulation of flaxseed oil in PCL using nanoprecipitation technology. Low-field NMR was employed to verify the encapsulation efficiency of the flaxseed oil.

Sample information:

One sample of encapsulated flaxseed oil and one sample of raw flaxseed oil (purchased from a local Suzhou laboratory to ensure both oils are from the same batch) were analysed using low-field NMR. The resulting relaxation spectra are shown below:

Figure: Relaxation spectra of encapsulated flaxseed oil and raw flaxseed oil

Conclusion

 

Comparison of the low-field NMR T₂ relaxation spectra of encapsulated flaxseed oil and raw flaxseed oil leads to the following conclusion:

The relaxation times of the encapsulated oil shift left on the axis compared to the raw oil, indicating that the molecular mobility of the oil is restricted by encapsulation. Low-field NMR successfully confirms the presence of encapsulated flaxseed oil within the product.

Besides food applications, low-field NMR can be used to assess encapsulation in pharmaceuticals, cosmetics, and other materials, providing a versatile, non-destructive evaluation tool.

References

 

[1] Zeev C W. 1H LF‐NMR Energy Relaxation Time Characterization of the Chemical and Morphological Structure of PUFA‐Rich Linseed Oil During Oxidation With and Without Antioxidants[J]. European Journal of Lipid Science and Technology, 2019, 121(9).

[2] Juan Francisco Nieto Alarcón, Santiago E V, Susana Hernández López. Determination of the Number of Epoxide Groups by FTIR-HATR and Its Correlation with 1H NMR in Epoxidized Linseed Oil[J]. Scientific & Academic Publishing, 2021(1).

[3] Su Y, Zhang S, Chen Y, et al. One-step synthesis of novel renewable multi-functional linseed oil-based acrylate prepolymers and its application in UV-curable coatings[J]. Progress in Organic Coatings, 2020, 148:105820.

[4] Resende M T, Linder C, Wiesman Z. 1H LF-NMR Energy Relaxation Time Characterization of the Chemical and Morphological Structure of PUFA‐rich Linseed Oil During Oxidation With and Without Antioxidants[J]. European Journal of Lipid Science and Technology, 2019.