Soybean Oil Content Determination by Magnetic Resonance

Oil and Moisture Content Testing via NMR

 

Oil and water are the two substances richest in hydrogen protons in nature. Since nuclear magnetic resonance (NMR) signals primarily originate from hydrogen, a higher number of hydrogen protons corresponds to a higher oil or moisture content, and vice versa. Therefore, by calibrating signal intensity, NMR can be used to accurately measure the oil and water content of a sample.

For measuring oil and water content in multi-component systems, international standards (ISO 10565) specify that water signals only appear before TE = 7ms. Thus, the peak at TE = 7ms in the CPMG echo train is used as the reference for calibrating and measuring oil content, establishing a linear relationship between reference sample oil content and signal. Water within the components decays faster than oil, so the difference between the total signal (approximated by the first major echo) and the oil signal (around TE = 7ms) represents the water signal in the sample. Similarly, a linear relationship can be derived for water content. This method is suitable for olives, sunflower seeds, rapeseed, peanuts, soybeans, maize, cottonseed, and more. (Currently, international standard ISO 10565:1995 “Oilseeds — Simultaneous Determination of Oil and Moisture Content — Pulsed NMR Method” and national standard GB/T 15690:1995 “Determination of Oil Content in Oilseeds by NMR” are in use.)

Here is a simple demonstration of soybean oil content testing

Reference samples and calibration lines are shown below:

Measurement of soybean oil content via NMR is shown below:

Most soybeans show oil content between 16–18%, with a few samples as low as 12–13%, which is below the oil content of imported soybeans (20–22%).

NMR technology requires no complex data models for measuring oil content — calibration with commercially available soybean oil is sufficient, and the testing process is completely non-destructive to the soybean.

Equipment used:

NMR Seed Oil Content Analyzer PQ001-12-040V