Effects of processing technologies combined with cell wall degrading enzymes on in vitro degradability of barley

Abstract

Effects of processing technologies and cell wall degrading enzymes on in vitro degradation of barley were tested in a 5 × 2 factorial arrangement: 5 technologies (unprocessed, wet-milling, extrusion, autoclaving, and acid-autoclaving), with or without enzymes. Upper gastrointestinal tract digestion (Boisen incubation) and large intestinal fermentation (gas production technique) were simulated in duplicate. All technologies increased digestion of DM (13 to 43% units) and starch (22 to 51% units) during Boisen incubation, compared with the unprocessed control (P < 0.01). Wet-milling, extrusion, and acid-autoclaving increased CP digestion by 29 to 33% units (P < 0.01). Xylanase and β-glucanase addition increased digestion of DM (≈ 20% units), starch (≈ 20% units), and CP (≈ 10% units) in unprocessed and autoclaved barley (P < 0.01). Wet-milling, extrusion, and acid-autoclaving, reduced the extent (50%) and maximum rate (60 to 75%) of fermentation (P < 0.01), which appeared to reflect the reduced amount of starch present in the Boisen residues. In conclusion, wet-milling, extrusion, and acid-autoclaving improved in vitro starch and CP digestion in barley, which is related to the cell wall matrix disruption. Addition of xylanases and β-glucanases improved in vitro starch and CP digestion only in unprocessed barley or barley poorly affected by processing.