[Comparison of fat determination methods and analysis of fatty acids in tea]

Objective: Comparative analysis of two method for determining fat and analysis of fatty acid content in tea samples.

Methods: The content of freefatand total fat in tea was determined by Soxhlet extraction method and acid hydrolysis method, and the content of fatty acids were determined by gas chromatography. The composition and content of fatty acids in 21 tea samples from 5 regions were analyzed.

Results: The freefat content of tea determined by Soxhlet extraction method was significantly lower than that determined by acid hydrolysis method. The totalfat content in tea determined by acid hydrolysis method was consistent with the total amount of fatty acids determined by gas chromatography, and their content conformed to the logical relationshipsimultaneously. The totalfat content in tea ranged from 0.6 to 4.1 g/100 g, which in green tea, white tea, yellow tea, and black tea were 2.2, 1.8, 1.6 and 0.6 g/100 g, respectively. The content of free fat in tea was less than 58%, with 42%-80% of the fat existing in a bound form. The fatty acids in tea were mainly unsaturated fatty acids, accounting for 67.52%-99.03% of the total fatty acids. There were differences in the composition of fatty acids in different types of tea, with the proportion of unsaturated fatty acids in yellow tea accounting for 98.84% of the total fatty acids, which was significantly higher than that of green tea, white tea, and black tea. The fatty acids with high content in green tea(except Tang chi xiaolan tea, Bawangjian green tea and Liuxi yuye tea)were α-linoleic acid, linoleic acid, and palmitic acid.

Conclusion: Theacid hydrolysis method is more suitable for the determination of fat in tea samples. The composition and content of fat and fatty acids in tea vary depending onfactors such as the type of tea and the degree of fermentation.