Barley spent grain: release of hydroxycinnamic acids (ferulic andp-coumaric acids) by commercial enzyme preparations

Barley spent grain is a residue from the brewing process. In this paper, four different commercial enzyme preparations (Viscozyme L, Ultraflo L, Termamyl and Lallzyme) were tested for their ability to release hydroxycinnamic acids, ferulic acid (FA) and p-coumaric acid (PCA), from barley spent grain. The cinnamic acid esterase activities of the enzyme preparations were measured against the model substrate methyl ferulate. Termamyl was the only enzyme preparation that showed no esterase activity. Incubation of Ultraflo L (1.3 U g−1 substrate, 24 h) with barley spent grain released 70% of the total alkali-extractable FA and 8% of the total alkali-extractable PCA. Under the same conditions, Viscozyme L and Lallzyme released, respectively, 33 and 55% of the total alkali-extractable FA, and 0.8 and 1.6% of the total alkali-extractable PCA. For FA release, enzyme concentrations higher than 1.3 U g−1 were saturating. However, for the release of PCA, a continuos increase was observed until 13 U g−1. The percentages of the FA released by Viscozyme L, Ultraflo L and Lallzyme were higher than those obtained by pure ferulic acid esterases. These three enzyme preparations could be employed for the effective release of hydroxycinnamic acids from barley spent grain.