Ferulic acid (FA) is the most abundant phenolic compound in wheat bran, an abundant and underused subproduct from the milling industry. FA shows potential commercial applications in the food, health and cosmetic industry, which is associated mainly to its antioxidant properties. Therefore, FA extraction from wheat bran constitutes a great alternative to add value to this plentiful subproduct.
FA can be found in three forms: soluble free, soluble conjugated and insoluble bound form, being most of it in the insoluble one: about 92% is ester-linked to the arabinoxylans and other cell-wall structural compounds. Alkaline hydrolysis is the method used as reference for the quantification of the total content of FA in the matrix, but alternative treatments, less aggressive and more environmentally friendly are desirable to be applied.
In our work, pressurized water extraction (PWE) was used and the analysis of the variables that influence its extraction (temperature, time and the addition of ethanol in the solvent) was tested. It showed that despite at ambient temperature FA is more soluble when ethanol is present, water was the most suitable solvent, indicating that the hydrolysis was the limiting step. It was also found that after certain conditions of temperature and time (160 ᵒC and 75 min), the amount of extracted FA started to decrease due to its thermal degradation, which was confirmed after obtaining the degradation curve of FA at the selected temperature.
Taking into account this results, other two treatments are proposed: supercritical water hydrolysis (SCWH) and microwave assisted extraction (MAE), as they are techniques that allow a fast heating reducing the time for FA degradation. Preliminary results from SCWH, using water at 400ᵒC and 250 bar for 0.2-0.5 seconds, showed amounts of extracted FA 3.5-fold higher than the obtained with PWE. On the other hand, in the MAE using water as solvent, the effect of solid:liquid ratio, temperature and time will be studied for the extraction of FA.
María Victoria Pazo Cepeda – Proyecto CTQ2013-44143-R