Use of glycoside hydrolase family 8 xylanases in baking Tony Collins a, * , Anne Hoyoux a , Agne `s Dutron c , Jacques Georis b , Bernard Genot b , Thierry Dauvrin b , Filip Arnaut c , Charles Gerday a , Georges Feller a a Laboratory of Biochemistry, Institute of Chemistry B6, University of Lie `ge, B-4000 Lie `ge, Belgium b Beldem-Puratos Group, Rue Bourrie 12, B-5300 Andenne, Belgium c Puratos Group, Industrialaan 25, Zone Maalbeek, 1702 Groot-Bijgaarden, Belgium Received 20 April 2005; revised 19 August 2005; accepted 19 August 2005 Abstract Xylanases have long been used in the baking industry for improving dough stability and flexibility and for increasing bread volume and crumb structure. Only xylanases from glycoside hydrolase families 10 and 11 appear to have been tested in this application and only those from the latter family have as yet found application. Interestingly, enzymes with a putative xylanase activity are also found in glycoside hydrolase families 5, 7, 8 and 43, but apparently these have not, as yet, been tested in baking. Baking trials were used to determine the effectiveness of a psychrophilic and a mesophilic family 8 xylanolytic enzyme as well as a psychrophilic family 10 xylanase and a currently used family 11 commercial mesophilic xylanase. The potential of family 8 xylanases as technological aids in baking was clearly demonstrated as both the psychrophilic enzyme from Pseudoalteromonas haloplanktis TAH3a and the mesophilic enzyme from Bacillus halodurans C-125 had a positive effect on loaf volume. In contrast, the psychrophilic family 10 enzyme from Cryptococcus adeliae TAE85 was found to be ineffective. q 2005 Elsevier Ltd. All rights reserved. Keywords: Xylanase; Baking; Glycoside hydrolase family 8 1. Introduction Xylanases are widely used as additives in the baking industry to improve processing and product quality. They have been shown to effect enhancements in dough and bread quality leading to improved dough flexibility, machinability and stability and a larger loaf volume as well as an improved crumb structure (Baillet et al., 2003; Guy and Sarabjit, 2003; Maat et al., 1992; Qi Si and Drost-Lustenberger, 2002). First introduced to the baking industry in the 1970s they are currently used frequently in combination with amylases, lipases and various oxidoreductases where specific effects on the rheological properties of the dough and organoleptic properties of the bread are desired (Qi Si and Drost-Lustenberger, 2002). While the exact mechanism of the functionality of xylanases in breadmaking has not as yet been fully elucidated, it is currently believed that the redistribution of water from the arabinoxylan in the flour to the starch and gluten phases is important (Ingelbrecht et al., 2000; Rouau et al., 1994). Flour generally consists of approximately 80% starch and 12% proteins, with arabinoxylan content varying from 2–3% in wheat flour (Baillet et al., 2003), up to 5% in wholemeal wheat flour and 8% in rye flour. The arabinoxylan, even though present in minor amounts, is an extremely important functional ingredient as it can bind almost ten times its own weight in water, accounting for almost 30% of the water binding capacity of wheat flour and hence exerts a significant effect on the flour and accordingly the dough and bread quality (Baillet et al., 2003; Courtin and Delcour, 2002). Arabinoxylans are complex polymers composed of a (1/4)-b-D-xylopyranosyl backbone chain substituted with a-L-arabinofuranose residues at the C(O)2 and/or C(O)3 positions which may themselves be further linked to glucuronic acid residues and/or ferulic acid groups (Fincher and Stone, 1986; Rubio, 2003). Arabinoxylans in wheat flour typically consist of approximately 20–25% of a water-extractable fraction which has a strong influence on the viscosity of the aqueous medium and a water-unextractable fraction which has an extremely strong water holding capacity and a negative effect on dough quality, being detrimental to Journal of Cereal Science 43 (2006) 79–84 www.elsevier.com/locate/jnlabr/yjcrs 0733-5210/$ - see front matter q 2005 Elsevier Ltd. All rights reserved. doi:10.1016/j.jcs.2005.08.002 Abbreviations: GH, glycoside hydrolase family; GH11 Xyl, family 11 mesophilic xylanase from Bacillus subtilis; IU, international units of xylanase activity; pXyl, glycoside hydrolase family 8 psychrophilic xylanase from Pseudoalteromonas haloplanktis TAH3a; Rex, glycoside hydrolase family 8 mesophilic enzyme from Bacillus halodurans C-125; X B , glycoside hydrolase family 10 psychrophilic xylanase from Cryptococcus adeliae TAE85. * Corresponding author. Tel.: C32 4 366 33 46; fax: C32 4 366 33 64. E-mail address: tcollins@ulg.ac.be (T. Collins).