Thermal and enzymatic treatments for the release of free ferulic acid from maize bran

Abstract

Different commercial enzyme preparations have been tested to release ferulic acid from maize bran. Best results were obtained with a preparation from Humicola insolens: Novozym 342. However, only 30% of the ferulic acid contained in the bran was released by Novozym 342; moreover, a part (1/3) of the solubilised ferulic acid was still esterified to sugars.Thermal pretreatment (flash-explosion or autoclaving at 160°C) has been tested in order to improve ferulic acid solubilisation. About 80% of ferulic acid contained in the bran was solubilised by a sequential procedure using first a flash-explosion pretreatment of the bran (10% w/v in water) at 180°C (1min) or 190°C (1min) followed after cooling by Novozym 342 treatment (3% w/w protein/bran at 40°C for 24h). Flash-explosion treatment solubilised feruloylated substrates and after Novozym 342 action about 1/3 of solubilised ferulic acid was still esterified to sugars.A similar 80% extent of solubilisation of ferulic acid as feruloylated oligosaccharides was also obtained by autoclaving maize bran (10% w/v in water) at 160°C for 1h. Subsequent treatment with feruloyl esterases was then necessary to get ferulic acid in its free form.