Extraction and Thermal Stability of Chlorogenic Acid from Green Coffee and Yerba Mate in Food-Based Solvents

Abstract

The development of phenolic-rich functional ingredients, particularly those containing 5-caffeoylquinic acid (5-CQA), is limited by the use of conventional organic solvents, such as ethanol and methanol. Therefore, this study aimed to select and develop food-based solvents for the extraction of 5-CQA from green coffee and yerba mate, proposing a functional ingredient that maintains its composition after thermal processing for food and pharmaceutical applications. Mixtures of citric acid, sorbitol, and betaine, already widely used as ingredients with preservative, sweetening, and nutritional properties, were selected on the basis of COSMO-RS predictions for 5-CQA extraction. Different molar ratios of three solvent systems containing 10% water, betaine:sorbitol (1:1, 1:2, 1:3, 1:4, and 1:5), betaine:citric acid (1:1, 1:2, and 2:1), and the ternary system betaine:sorbitol:citric acid (1:1:1) were employed in the extractions. Among the evaluated systems, the 1:5 betaine:sorbitol, 1:2 betaine:citric acid, and ternary mixtures were effective for bioactive compound extraction and displayed DSC thermograms consistent with the formation of deep eutectic solvents (DESs). The 1:2 betaine:citric acid showed the highest extraction efficiency for 5-CQA, likely because of its lower pH (2.6). An acidic medium helps to retain its protons, preventing oxidation or isomerization. Phenolic compounds in coffee extracts were thermally stable in all solvents except 1:5 betaine:sorbitol, which may be due to its less acidic pH (5.95). Compounds in yerba mate extracts produced with 85:15 water:ethanol showed isomerization of 3-CQA into 5-CQA, whereas the formulated solvents reduced the thermal effect. Thus, food-based DESs efficiently extracted and thermally protected 5-CQA, showing strong potential for functional food applications.