Standards Development
This document specifies the principles, reagents and materials, apparatus, preparation of the test sample, procedures, expression of results, precision requirements and test report for the determination of gossypol in vegetable fats and oils using ultra-high performance liquid chromatography-tandem mass spectrometry.
— The method is applicable to the determination of free gossypol content in vegetable fats and oils.
— The limit of detection (LOD) of the method is 10 g/kg and the limit of quantification (LOQ) is 50 g/kg.
Gossypol, a polyphenolic compound inherent to cottonseed, predominantly persists as a residue in cottonseed oil and cottonseed cake meal during the cottonseed oil extraction process. It exists in both free and bound forms, and the free gossypol is toxic to humans and animals. Furthermore, the high content of free gossypol in cottonseed oil pose significant toxicological risks, particularly to the nervous system, vascular tissue, and reproductive system of animals. Chronic ingestion of cottonseed oil with high content of free gossypol may cause poisoning. Recognizing the potential health hazards associated with free gossypol, the Food and Drug Administration (FDA) and the World Health Organization (WHO) have set maximum permissible levels of free gossypol in food at 450 mg/kg and 600 mg/kg, respectively. In China, the 'State Food Safety Standards for Vegetable Oil (GB 2716)' establishes a maximum permissible limit of 200 mg/kg for free gossypol in cottonseed oil. Currently, the primary analytical techniques for the quantification of gossypol in vegetable oils encompass the aniline method, UV spectrophotometry, thin-layer chromatography (TLC), and high-performance liquid chromatography (HPLC). While these methods exhibit distinct differences in terms of stability, susceptibility to interference from other components, and detection limit. In contrast, the HPLC is a preferred analytical technique for determining gossypol in edible oils due to its exceptional sensitivity and stability. According to the GB 5009.148 (State Food Safety Standards for the Determination of Gossypol in Plant Foods), the HPLC method is capable of achieving a limit of quantification (LOQ) of 7.5 mg/kg and a limit of detection (LOD) of 2.5 mg/kg for gossypol in vegetable oils.
In recent years, the global supply and demand for cottonseed oil have remained relatively stable, with approximately 5 million tons per year, in which China and India hold significant market shares, estimated at 30% and 25%, respectively. Despite this stability, the market presence of cottonseed oil as a commodity is limited, and there is an observed practice of its illicit substitution into higher-value edible oils (such as olive oil, sesame oil, peanut oil, etc.) by some unscrupulous entities. A notable case of 'black heart oil' emerged in Taiwan, China, in 2013, where olive oil was adulterated with cottonseed oil, reaching a concentration of up to 40%. Gossypol, a distinctive compound present in cottonseed oil, serves as a marker for detecting the adulteration of edible oils with cottonseed oil. Consequently, Taiwan has established a regulatory limit of 1 mg/kg for gossypol in edible oils.
This document specifies an ultra-high performance liquid chromatography-tandem mass spectrometry (UPLC-MS/MS) method for the determination of free gossypol in vegetable oils. The method leverages the separation capabilities of UPLC for compounds and the high selectivity and sensitivity of mass spectrometry to accurately quantify free gossypol. It achieves a LOD as low as 10 g/kg and reduces the analysis time by approximately 50% compared to the conventional HPLC method. When compared to the current method standards for detecting gossypol content, this standard fulfils the requirements for detecting trace amounts of gossypol in vegetable oils. The implementation of this standard will provide the necessary technical support to combat the illegal adulteration of vegetable oils with cottonseed oil. This will not only enhance the monitoring and surveillance of edible vegetable oils, ensuring the protection of legitimate interests from consumers, but also contribute to the standardization of the vegetable oil trade.
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