Extraction of different phenolic groups from oats at a nonthermal pilot scale: Effect of solvent composition and cycles

Abstract

AbstractThis article explores oat's polyphenols extraction in ethanol/water and methanol/water at a nonthermal pilot scale. Alcohol % (vol/vol) and cycles were controlled by response surface methodology. Eight polyphenols were evaluated (HPLC), together with antioxidant capacity (ORAC) and total polyphenol content (TPC). Model adjusted well in the majority of the cases. Highest TPC and ORAC were obtained with ethanolic mixtures. Vanillic acid and vanillin highest yields were at 14.6% (vol/vol) and 50% (vol/vol) in both alcohols. Hydrocinnamic acids were better extracted at high alcohol concentrations (98–100%, vol/vol), where p‐coumaric acid was the most present. Avenanthramides optimum alcohol extraction composition varied from 50 to 100% (vol/vol). Hence, different polarity behavior was observed (2c > 2f > 2p). Avenanthramide 2c showed the highest yield. Cycles effect varied depending on the polyphenol evaluated, they were more necessary for the extraction of p‐coumaric acid and avenanthramide 2f. Results aid to understand solvation process for a more efficient polyphenols extraction.Practical applicationsThe research fills the gap between reported laboratory work and the lack of experimental scale up data. It considers scale up aspects such as developing a simple and easy to scale process (ambient temperature and 8 bars pressure) and using food grade solvents. Extractions were run with a controlled particle size distribution rather than a specific particle size. A small solvent/solid ratio was kept, since excessive amount of solvent generates expensive downstream operations. Moreover, solvent was reused on each run until the necessary cycles were completed. The optimization here presented will allow a better understanding in the extraction of oat's polyphenols; individually, as group, and total. This will aid for a more robust polyphenols extractions from oat at the food industry.