Cooking Oil Testing

Xu, Baocheng, et al. Food chemistry 245 (2018): 415-425.

Plant sterol profiles have been used for the characterization and identification of vegetable oils and are often employed as markers for detecting oil adulteration. Consequently, the study of plant sterols, particularly sterols in vegetable oils, has garnered interest among scientists.

A method was developed using comprehensive two-dimensional gas chromatography coupled with time-of-flight mass spectrometry (GC×GC-TOF/MS) for the analysis of steroidal compounds in vegetable oils. This method offers better resolution and higher sensitivity compared to traditional one-dimensional gas chromatography, allowing for the determination of 31 types of sterols and triterpenols in a single injection. Additionally, the method enables the separation and detection of small amounts of other compounds (potentially unidentified steroidal compounds) that are masked in lower-resolution single-column techniques. The GC×GC system facilitates a more detailed and comprehensive assessment of the distribution and concentration of free sterols and triterpenols in safflower seed oil, soybean oil, canola oil, sunflower seed oil, and peanut oil.

Zhang, L., Wang, S., Yang, R., Mao, J., Jiang, J., Wang, X., ... & Li, P. (2019). Food Chemistry, 289, 313-319.

A method has been established fo sed on ultrasound-assisted saponification, liquid-liquid extraction, and liquid chromatography-tandem mass spectrometry (LC-MS/MS).

The sample treatment involved ultrasound-assisted saponification at a temperature of 75°C for 40 minutes. The limits of detection and quantification ranged from 2.0 to 3.2 ng/mL and 6.1 to 10.0 ng/mL, respectively. A linear correlation (R² > 0.99) was achieved, with recovery rates at three spiking levels ranging from 81.7% to 112.0%.

Using this method, eight compounds were quantified in camellia oil and olive oil. The results indicated that the levels of stigmasterol, δ-tocopherol, γ-tocopherol, β-carotene, and lutein in camellia oil were significantly higher than those in olive oil (p < 0.05). This method can successfully be applied to the determination of these eight active components in camellia oil and other edible oils.

Cai, M., Chen, X., Wei, X., Pan, S., Zhao, Y., & Jin, M. (2014). Food chemistry, 158, 459-465.

A rapid and accurate method for the determination of ricinoleic acid in edible oils has been established using positive electrospray liquid chromatography-tandem mass spectrometry (LC-MS/MS).

Homogenized samples were extracted with ethanol/water (20:80, v/v), and ¹³C₆-labeled ricinoleic acid was added as an internal standard. Purification was performed using dispersive solid-phase extraction (dSPE) with primary-secondary amine (PSA) and C18 as adsorbents. The extracts were separated using methanol/water (25:75, v/v) as the mobile phase on a short C18 reverse-phase column, and detection was carried out in multiple reaction monitoring (MRM) mode, with absolute matrix effects ranging from 93.2% to 102.2%.

Ricinoleic acid exhibited good linearity in the range of 0.5–50.0 μg/kg, with a limit of quantification of 0.5 μg/kg. Recovery rates ranged from 86.0% to 98.3%, and the intra-day and inter-day relative standard deviations (RSD) were 2.6% to 7.0% and 5.5% to 10.8%, respectively. This method is suitable for the rapid quantitative analysis of ricinoleic acid in edible oils.