Application Notes
Published: 01 Jul 2023 · Last updated: 03 Aug 2026
Solid Fat Content (SFC) is an essential measurement for characterising edible oils/fats used in the bakery, confectionery and margarine industries for which a rapid and convenient method is required.
The melting profile (Solid Fat Content vs. Temperature) determines the specific application of the edible oil/fat thus is an important quality control parameter for both the suppliers and end users, as well as for the purpose of product development. Increasing legislation associated with reducing or eliminating trans fatty acids has caused renewed interest in the method since many conventional products will need to be reformulated.
The traditional method for measuring SFC has been dilatometry but this is regarded as slow, inaccurate and cumbersome. However, for a number of years Nuclear Magnetic Resonance (NMR) has been the method of choice for the determination of SFC.
The Direct Method works by measuring both the solid and liquid signals from the NMR Free Induction Decay (FID) of the sample. This is possible because signals from solids decay much faster than signals from liquids. It is therefore possible, in principle, to take measurements at two points on the FID (Figure 1), at point S0, corresponding to the total solid plus liquid signal, and another at point S70 which corresponds to the liquid only signal, after the solid signal has died away. Simple arithmetic yields the percentage of Solid Fat which is given by (S0 − S70)/S0 × 100. In practice, it is not possible to take a measurement at point S0, immediately after the 90° radio frequency (RF) pulse. The short, high power RF pulse causes the sample probe to ‘ring’ for a few microseconds during which time measurements cannot be made. Instead, the first measurement is taken immediately after this ringing period (or dead time), at point S11. Given that S11 does not represent the total signal from the solid and liquid, a correction needs to be applied. This correction assumes a fixed ratio (known as the f-factor) between S0 and S11 due to loss of the solid signal during the first 11 μs of the decay.
Fig. 1 — Schematic diagram showing how Solid Fat Content is derived from NMR measurements by the Direct Method.
Official methods also exist for the Indirect Method which measures the liquid signal only (an absolute measurement) and must therefore be referenced against the same sample when fully melted. As a consequence, the Indirect Method requires an additional temperature step as well as a temperature compensation sample, and care must be taken to keep all sample within the measurement volume of the probe.
In contrast, the Direct Method is a ratio measurement which is not sensitive to sample loading and does not require a compensation sample or an additional temperature step. The Direct Method is the preferred NMR method for determining SFC.
Before measuring the SFC, edible oil and fat samples must be tempered in order to stabilise their crystal structures. The tempering process involves placing the samples in temperature controlled blocks for set periods of time. After melting the samples at 100°C, they are pre conditioned at 60°C and then 0°C to eliminate their thermal history. Stabilizing fats such as cocoa butter require a different temperature regime. Thereafter the samples are stabilised at a variety of temperatures of interest prior to NMR analysis. This may be carried out on the same sample in ‘Series’ or multiple aliquots of a sample in ‘Parallel’. The Parallel method is usually preferred since it is faster, however it does require a separate conditioning block for each temperature, in addition to those for the preconditioning steps.
The number and value of the temperature steps, and the time that the samples are at each temperature are set by the official method being followed, such as the International Organisation for Standardization (ISO 8292-1), the American Oil Chemists’ Society (AOCS Cd 16b-93), or the International Union of Pure and Applied Chemistry (IUPAC 2.150). Further details concerning the official methods are available from the respective organisations.
Fig. 2 — Graph showing melting profiles (Solid Fat Content vs. Temperature) of AOCS proficiency samples.
An automatic software routine determines the f-factor using samples of known SFC. Artificial standards are supplied by the NMR manufacturer and are designed to represent approximately 0%, 30% and 70% SFC. Exact values are assigned and certified by the manufacturer.
Figure 2 shows the results from three AOCS proficiency samples used to validate the instrument. The two most important factors in obtaining consistent results between laboratories, both of which are independent of the instrument, are:
Oxford Instruments offers a package especially tailored to the measurement of Solid Fat Content:
In addition to the above, the following are also required:
The MQC+ SFC analyser offers multiple advantages over other instruments on the market:
© Oxford Instruments 2026