Rising the nutritional value of pastry products is important since the enriched products can be used for special aims as developing countries or special diets (Majzoobi et al., 2012). Wheat germ, a highly nutritive part of wheat kernel is a milling industry by-product which has remarkable nutritional characteristics. However, it has limited usage due to a high risk of rancidity, which can be reduced via usage of some thermal treatments such as extrusion. The aim of this study was to check of how wheat germ additive affects the changes to quality of dough. For this case, some different amounts of extracted wheat germ are added to dough and then investigate the differences including: Rheological characteristics of the dough and quality characteristics of the bread both physical and the sensory points of view. (Gómez et al., 2012). Wheat germ has a low shelf life. In order to raise its life quality, so that it can be used into different products. Different heat treatments are applied on composition of wheat germ. (Srivastava et al., 2007).
Wheat has a long history of cultivation, dating back to at least 6750 B.C.(Khush, 1997), and is the most important grain food in the moderate temperate zones of the world. Wheat is classified into at least ten Triticum species, of which six are cultivated. Triticum aestivum L. includes five subspecies; most common wheat speciese are (Triticum aestivum L. subspecies aestivum).Wheat germ is an important source of several vitamins, minerals, and other phytonutrients, including apigenin and luteolin-based flavonoids(Liangli, 2008). Hence it is available as a separate entity because it is an important source of vitamin E. Wheat germ has only one half the glutamine and proline of flour, but the levels of alanine, arginine, asparagine, glycine, lysine and threonine are double(Hemery et al., 2007). This by-product is characterized by its high protein content (over 20%), mainly in the form of albumins and globulins, and its better-balanced amino acid composition, due partly to its higher lysine content than endosperm. Furthermore, wheat germ has components with high antioxidant activity .In vitro analysis has also demonstrated that it has a beneficial effect on the growth of human bifidobacteria. Consequently, wheat germ is a product with very interesting nutritional characteristics and with a significant potential for use as a supplement in specific formulations(Phillips and Williams, 2009). This by-product of milling also has a considerable fat content of around 10 g/100 g, and a significant quantity of bioactive molecules related to its role as part of the embryo of a new plant. Among these bioactive molecules, the lipases and the lipoxygenases can hydrolyze lipids and initiate the oxidative rancidity process(Galli et al., 2017). This fact and the high unsaturated fatty acid content of wheat germ lead to the short shelf-life of raw germ or even flours with germ. Furthermore, raw germ weakens bread dough due to the presence of glutathione, a powerful reducer that weakens the gluten network by the breaking disulphide bonds(Kamel and Stauffer, 1993). A number of treatments have been proposed to increase wheat germ shelf-life, including conventional or microwave heating. Due to the nutritional interest of wheat germ and the possibility of using a by-product from the milling industry, the addition of raw wheat germ or its derivate to baking products has been studied using various approaches. Some of those studies were based on the addition of raw wheat germ, but others incorporate defatted wheat germ, heated wheat germ, or a combination of the two to obtain products with a longer shelf life and better functional properties than raw wheat germ. In most cases, the heating method was toasting or steaming. Extrusion cooking is a rapid, high-temperature technique for the production a wide range of food products. During extrusion of th wheat germ oil to a combination of humidity, pressure, temperature and mechanical shear. This method has a number of advantages: a reduction of the microbial content of the food; partial inactivation of enzymes and some anti-nutritional factors; modification of starch, lipid, protein, and fiber structure; and, to some degree, a reduction in vitamin content, modifying the nutritional and functional properties of the product. As this process enables the wheat germ to be stabilized by applying a high temperature, it can be counted to be an alternative to other heating treatments. The aim of this study is to determine how the extrusion process affects the ability of wheat germ to be used in bakery products. This is done through an analysis of the influence of adding different quantities of extruded and raw wheat germ on the rheological characteristics of dough and on the final quality of bread, from both the physical and the sensory points of view(Majzoobi et al., 2012).