Design of experiments for green and GRAS solvent extraction of phenolic compounds from food industry by-products- A systematic review

Concerning the high impact of climatic change in the environment, the scientific community has focused on a circular economy perspective and the revalorization of waste generated by the food industry for bioactive uses. These applications are possible due to the presence of bioactive compounds in these food wastes. In this sense, phenolic compounds highlight for their positive health implications, as they possess potent activity to prevent diseases such as cancer, inflammation and obesity, among others. For this purpose, the optimized extraction of these target compounds from by-products with a novel green chemistry approach, by using environmentally clean and friendly extraction techniques, commonly known as green extractions, as well as those permitted in foods and safe for health (GRAS solvents) is commonly applied. Following this research line, a systematic review was conducted using different databases (Web of Science, PubMed and Scopus) following PRISMA guidelines to assess the optimization of different green and GRAS solvent extraction techniques from food by-products, the best extraction conditions, as well as the experimental design applied to obtained maximum amounts of the compounds of interest, considering the research published to date. Thus, 67 studies of 282 records identified met the inclusion criteria. A distinction has been made between the different technologies used in the extraction processes, paying special attention to the experimental designs applied and the optimized independent variables. Finally, a quantitative and qualitative comparison was made between the different matrices studied.