ReviewRecent advances in the processing of green tea biomolecules using ethyl lactate. A review

- Solvent extraction of caffeine from green tea leaves is reviewed.
- Ethyl lactate is an agrochemical green solvent adequate to extract food compounds.
- Ethyl lactate is selective and efficient for removing caffeine from plant matrices.
- Caffeine-free and catechins-rich precipitate is produced by ethyl lactate/SAS technique.

BackgroundGreen tea and its decaffeinated products are foodstuffs which involve a great commercial market due to their interesting healthy properties. Catechins are the main phenolic compounds in tea leaves and these are receiving considerable interest due to their potential benefits on human health. In this sense, many studies have been performed with the aim of removing the caffeine and obtaining either decaffeinated green tea leaves preserving the catechins or decaffeinated catechins-rich extracts.Scope and approachIn this review, different methods and solvents described in the literature for green tea decaffeination and recovery of high valued catechins are revised. Particular attention is given to ethyl lactate, an agrochemical green solvent studied by the authors for the extraction of caffeine.Key findings and conclusionsA diversity of results has been reported for the different green solvents and extraction techniques studied to remove caffeine from green tea leaves and extracts in the last years. Nevertheless, despite the solvent used, the loss of catechins is unavoidable to some extent. In this sense, ethyl lactate has demonstrated higher selectivity and efficiency with respect to commercial and other agrochemical solvents currently used to that end. Additionally, combining ethyl lactate with Supercritical CO2 Anti-Solvent technique, a decaffeinated green tea precipitate could be obtained, overcoming limitations of presently studied procedures to obtain decaffeinated extracts and demonstrating to be a selective and effective alternative for catechins purification.