Recuperación de ácido cafeico de disoluciones acuosas mediante extracción de punto de turbidez con tensioactivos no iónicos

Abstract

Food waste has become one of the main problems around the world. More than 85 million tons of food are wasted per year in the European Union, and this waste is generated at different stages throughout the entire food chain. One of the main challenges facing the food industry is being able to minimize or reuse the high amount of waste generated during food processing, which represents a very significant challenge at an environmental, social and economic level. In recent years, different treatments have been proposed for the treatment of these wastes, in order to recover the high added-value compounds present in them for subsequent use, mainly in agri-food, pharmaceutical and cosmetic industries. Among these compounds, the polyphenols present in plants, fruits and vegetables stand out. Polyphenols are bioactive compounds with low solubility in water and are very beneficial for human health due to their antioxidant properties and their ability to prevent chronic diseases such as obesity, cardiovascular diseases and different types of cancer. The most commonly used techniques for the extraction and recovery of polyphenols are not very sustainable and are harmful to the environment, since they use toxic organic solvents. Clean technologies have been investigated as alternatives for the recovery of these compounds in a more economical and environmentally sustainable way. The main objective of this work was to study the technical feasibility of a cloud point extraction process using non-ionic surfactants for the recovery of a model polyphenol (caffeic acid) from aqueous solutions, avoiding the use or organic solvents and allowing the recovery and reuse of these compounds, promoting circular economy and sustainability practices in the food industry. Three non-ionic surfactants were tested, among which Triton X-114 (15% w/v) was selected for subsequent extraction experiments due to its lower cloud point. A design of experiments was performed using response surface methodology (RSM) and central composite design (CCD) for the evaluation of the effect of three factors (temperature, extraction time and salt (NaCl) concentration) on the caffeic acid extraction degree from aqueous solutions (500 mg/L caffeic acid) and the optimization of the operating conditions used in the cloud point extraction process. Caffeic acid content (Folin-Ciocalteu method) and antioxidant capacity (BRS voltammetric method) of the aqueous phases and extracts (surfactant-rich phase), respectively, obtained after cloud point extraction were also determined. The following optimum operating conditions were obtained: temperature of 40 ºC, 40 minutes of extraction time and 10% (w/v) salt concentration (NaCl) added to the feed to lower the cloud point and promote phase separation. For these optimum operating conditions, the model proposed in the design of experiments predicted a caffeic acid extraction degree of 97.22%. Experimentally, a 95.86% of caffeic acid extraction was obtained working under the aforementioned optimum operating conditions. This percentage increased to 97.55% when the extraction was carried out in two stages, obtaining an extract with a high antioxidant capacity (2804.2 ± 91.7 BRS units). The use of the cloud point extraction process proposed in this work would contribute to achieving some of the Sustainable Development Goals (SDGs), such as SDG 9 (Industry, innovation and infrastructure) and SDG 12 (Responsible consumption and production).