Food Engineering, Materials Science, & Nanotechnology Effect of Germination and Extrusion on Physicochemical Properties and Nutritional Qualities of Extrudates and Tortilla from Wheat Lijia Zhu , Akinbode A. Adedeji, and Sajid Alavi Abstract: Wheat is the most common grain in the temperate region. Modifying its constituent through food processing improves its functionality and nutrient access. In this study, the combined effect of germination and extrusion on physicochemical properties and nutritional qualities of extrudates and tortilla from wheat was evaluated. Results showed that germination significantly increased (P <0.05) the γ -aminobutyric acid content in germinated whole wheat (GW) and extruded germinated whole wheat (EGW) as compared to the control of whole wheat (WW). Germination also significantly increased the protein content, reducing sugar and total soluble sugar content in GW, while extrusion had much increasing impact on reducing sugar content in extruded samples. Specific mechanical energy during extrusion was reduced as feed moisture content increased from 20 to 30%. Higher extruder screw speed (350 rpm) led to better expansion ratio at low moisture content (20%) as compared to low screw speed (200 rpm). Extrusion significantly increased the starch digestibility but decreased the protein digestibility in extrudates. Tortilla made from 100% WW had about the same physical characteristics, namely color and rollability, with tortilla made from 85% WW with 15% GW, 85% WW with 15% extruded whole wheat (EW), and 85% WW with 15% EGW. Tortilla made from 85% WW with 15% GW showed the largest diameter, thinnest thickness and least extensibility. A 15% extruded germinated wheat (350 rpm) addition in 85% WW showed significant increase of γ -aminobutyric acid content in tortilla compared to the control (100% WW). Keywords: γ -Aminobutyric acid, digestibility, extrusion, germination, tortilla, wheat Practical Application: It is technically feasible to substitute part of the wheat flour in tortillas with extruded germinated wheat without significantly affecting product qualities. A 15% extruded germinated wheat (350 rpm) addition in 85% whole wheat showed significant increase of γ -aminobutyric acid in tortilla compared to the control. This paper opens opportunities for manufacturers to create and promote healthier versions of tortillas to the market. Introduction Germination or sprouting is a process that harnesses the stored nutrient content of a seed in the presence of sufficient water and proper temperature, in order to cause growth of a plant. Ger- mination is also a common problem for grain at high humid- ity conditions during harvest and/or storage (Wrigley and others 1994). The results from wheat field trials in Esperance Australia during 2003 to 2004 indicated that the combined reduction in yield over 7 wk can range from 10% to 20% depending on the severity of sprouting. Wheat grain yield losses of 10% to 50% have been recorded in years with exceptional sprouting events (Biddulph and others 2005). Therefore, finding value-added use for sprouted wheat would reduce losses and balance return for wheat producers. Germination, on the other hand, is a well-known biochemical process used to make malt for the brewing industry or malted flour, JFDS-2017-0168 Submitted 1/27/2017, Accepted 6/2/2017. Authors Zhu, Ad- edeji, and Alavi are with Dept. of Grain Science and Industry, Kansas State Univ., Manhattan, KS 66506, U.S.A. Author Zhu is with School of Food Science, Univ. of Idaho, Moscow, ID 83843. Author Adedeji is with Dept. of Biosystems and Agricultural Engineering, Univ. of Kentucky, Lexington, KY 40546, U.S.A. Direct inquiries to author Sajid Alavi (E-mail: salavi@ksu.edu). which can also be used in bakery products, nonalcoholic drinks, and weaning food formulations. In this regard, germination is un- dertaken as a processing step in activating enzymes that have been dormant in the dry grain kernels. During this process, intrin- sic enzymes, such as amylases, proteases, lipases, fiber-degrading enzymes and phytases, disrupt and hydrolyze proteins, carbohy- drates and lipids to simpler molecules. This leads to increased digestibility of these substances and enhances their bioavailability and bioaccessibility when consumed by human or animal (Manna and others 1995; Dicko and others 2006; Yan and others 2009). Apart from improving the digestibility, biochemical activities oc- curring during germination can generate bioactive compounds such as antioxidants (γ -aminobutyric acid or GABA, ferulic acid, γ -oryzanol) (Frias and others 2005; Komatsuzaki and others 2007; Singkhornart and others 2013) and also lower the levels of antinu- tritional factors such as tannins, phytic and oxalic acids (Dicko and others 2006; Correia and others 2008; Paucar-Menacho and others 2009). Developing processes that mobilizes bioactive compounds in grains is of emerging interest, because it may significantly en- hance the nutrition, function, as well as improve palatability of grain-based foods (Singh and Sharma 2017). Health benefits of GABA have been reported in lowering blood pressure (Imam and others 2012; Matsuo and others 2012; Zhang and others 2014) and blood cholesterol (Usuki and others 2011), exhibiting greater kidney and liver activity (Kim and others 2004), inhibiting C  2017 Institute of Food Technologists R  doi: 10.1111/1750-3841.13797 Vol. 00, Nr. 0, 2017  Journal of Food Science 1 Further reproduction without permission is prohibited