Journal of Cereal Science 93 (2020) 102941 Available online 29 February 2020 0733-5210/© 2020 Elsevier Ltd. All rights reserved. Effect of extrusion treatment on enzymatic hydrolysis of wheat bran Eda Aktas-Akyildiz a, b, * , M. Tugrul Masatcioglu c , Hamit K€ oksel a, d a Food Engineering Department, Hacettepe University, Ankara, Turkey b Food Engineering Department, Hitit University, Corum, Turkey c Food Engineering Department, Hatay Mustafa Kemal University, Hatay, Turkey d Nutrition and Dietetics Department, Istinye University, Turkey A R T I C L E INFO Keywords: Wheat bran Dietary fbre Extrusion Enzymatic hydrolysis ABSTRACT Although, wheat bran is a good source of dietary fbre (DF), it has certain disadvantages due relatively lower levels of soluble DF. Therefore, in the current study, the effect of extrusion treatment on microstructure and enzymatic hydrolysis of wheat bran was investigated. Extrusion treatment increased fbre solubility at all process conditions and the screw speed was found to be the most effective parameter. Physicochemical properties of bran were affected from extrusion treatments. While the water-binding capacities of extruded brans were lower than that of non-extruded wheat bran, their water solubilities were higher. Enzymatic hydrolysis increased the soluble DF content of the bran samples as compared to those of respective samples at the beginning of incubation. The results showed that extrusion treatment can be used to disrupt the wheat bran microstructure and thus to in- crease the soluble fbre content. Enzymatic hydrolysis can also be used for increasing solubility further. The outcomes of this study can be utilized for improving the technological functionality of cereal fbres to develop high fbre ingredients for food applications. 1. Introduction Dietary fbre (DF) is an important food component that has benefcial roles in human health. It can delay gastric emptying, decrease post- prandial blood glucose and insulin levels, increase satiety, increase bacterial mass in the colon and thus increase faecal mass, decrease transit time, bind bile acids and increase short-chain fatty acid pro- duction and thus lowers blood cholesterol. Therefore, it may protect against some chronic diseases such as cardiovascular diseases, obesity, diabetes, gastrointestinal diseases, and some types of cancers (Anderson et al., 2009; Thebaudin et al., 1997). Wheat bran is a by-product of milling which is rich in DF. However, supplementation of bran in food formulations has adverse effects on consistency, texture, rheological and sensorial characteristics of fnal products; therefore, supplementation level has been limited (Guillon and Champ, 2000). Insoluble fbre is the major component mainly responsible for the negative technological effects of wheat bran; thus, increasing solubility of wheat bran fbres by processing is expected to improve the application potential of bran in food products (Aktas-A- kyildiz et al., 2017; Guillon and Champ, 2000). Extrusion is a combination of thermal and mechanical treatments where the material is subjected to high temperature and shear for a short time. The extrusion process is used to modify or texturize food materials. Studies have shown that extrusion cooking might have positive effects on total and soluble DF (Yang et al., 2017). It was reported in several studies that soluble fbre content of cereal bran increased by extrusion treatment (Gualberto et al., 1997; Ralet et al., 1990), while a decrease was observed in anti-nutritional components such as phytic acid (Kaur et al., 2015). It was also reported in the literature that the enzymatic incubation increased the solubility of fbres (Nordlund et al., 2013; Wen et al., 2017). However, there are only a few studies available on the effect of extrusion cooking and enzyme treatment on fbre solubility, and those were mostly about bioconversion of lignocellulosic materials prior ethanol production. Therefore, the aim of this study was to modify wheat bran by combination of extrusion and enzymatic treatments to improve solubility and hydration properties of wheat bran to be used in food applications. * Corresponding author. Hitit University, Çevre Yolu Bulvarı No:8, Corum, Turkey. E-mail address: edaaktas@hitit.edu.tr (E. Aktas-Akyildiz). Contents lists available at ScienceDirect Journal of Cereal Science journal homepage: http://www.elsevier.com/locate/jcs https://doi.org/10.1016/j.jcs.2020.102941 Received 29 August 2019; Received in revised form 25 February 2020; Accepted 28 February 2020