Malting of barley with combinations of Lactobacillus plantarum, Aspergillus niger, Trichoderma reesei, Rhizopus oligosporus and Geotrichum candidum to enhance malt quality

Good quality malt is characterised by the presence of high levels of fermentable sugars, amino acids and vitamins. To reach the starch-rich endosperm of the kernel, β-glucan- and arabinoxylan-rich cell walls have to be degraded. β-Glucanase is synthesized in vast quantities by the aleurone layer and scutellum during germination. Secretion of hydrolytic enzymes is often stimulated by addition of the plant hormone gibberellic acid (GA3) during germination. We have shown an enhanced β-glucanase and α-amylase activity in malt when germinating barley was inoculated with a combination of Lactobacillus plantarum B.S1.6 and spores of Aspergillus niger MH1, Rhizopus oligosporus MH2 or Trichoderma reesei MH3, and L. plantarum B.S1.6 combined with cell-free culture supernatants from each of these fungi. Highest malt β-glucanase activity (414 Units/kg malt) was recorded with a combination of L. plantarum B.S1.6 and spores of A. niger MH1. Highest α-amylase activities were recorded with a combination of L. plantarum B.S1.6 and spores of R. oligosporus MH2 (373 Ceralpha Units/g malt). Highest FAN levels were recorded when L. plantarum was inoculated in combination with spores of either R. oligosporus MH2 or T. reesei MH3 (259 and 260 ppm, respectively). This is the first study showing that cell-free culture supernatants of Aspergillus, Rhizopus and Trichoderma have a stimulating effect on β-glucanase and α-amylase production during malting. A combination of L. plantarum B.S1.6, and spores of A. niger MH1 and R. oligosporus MH2 may be used as starter cultures to enhance malt quality.