الفهرس 
REVIEW OF LITERATUREOnly 14 pages are availabe for public view
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Abstract
Over the last decades, consumer demands in the field of fabricated food production have changed considerably. For this reason, foods today are not intended only to satisfy hunger and to provide necessary nutrients, but also to prevent nutrition-related diseases and enhance physical and mental well-being of consumers. In this regard, functional foods offer an outstanding opportunity to improve the quality of products. Early functional foods were characterised by fortification with vitamins and/or minerals and dietary fibre (Betoret et al., 2011).
Bread is an important ingredient of human daily diet almost in every country of the world. It is a source of nutrients especially carbohydrates, fiber, proteins and some minerals (magnesium, phosphorus, iron). Freshness of bread is short and it is one of the major factors in consumer acceptance (Rosell et al., 2009).
An increased consumer demand for healthy bread has led to considerable efforts to develop breads that combine health benefits with good sensory properties. The use of whole grain wheat flour is one strategy for the development of healthy breads as the consumption of whole grain has been shown to reduce the risk of colorectal cancer, cardiovascular diseases, diabetes and obesity (Topping, 2007). It is believed that the high content of dietary fibre in whole grain plays a significant role in the health promoting effect. However, other whole grain components such as phenolics may also be involved (Slavin, 2004). Increasing the content of cereal β-glucan in the breads is another strategy to improve their nutritional quality. Cereal β-glucans are known for their ability to lower postprandial serum glucose levels and insulin response and to lower serum cholesterol levels (Brennan and Cleary, 2005). The high content of β-glucan in barley (2.5-11.3%) compared to wheat (0.4-1%) has made barley increasingly interesting for bread production (Lazaridou et al., 2007).
Wheat is the most common cereal used for bread production in Egypt. Flour constitutes one of the essential ingredients for a wide range of breads, noodles, cakes, and other bakery products. Also, wheat is consumed in the form of semolina for production of a variety of pasta products and couscous. In Egypt, wheat flour bread represents the main staple food for most people.
Commercial white bread is lacking in some essential nutritional compounds. However, composite flour substituted with a partial substitution of another grain flour for wheat flour can improved the bread nutrient quality (e.g., dietary fibre, essential minerals and resistant starch). In addition to the nutrients, the composite breads contributed to the flavour and colour, which may not be observed in most common white breads (Hathorn et al., 2008). Much of the work conducted on wheat flour substituted with non-wheat flour in bread formulations has aimed to improve the bioactive compounds of the bakery products (Ragaee et al., 2011). However, there is an increase in new food products with barley, including breads, mainly due to the content of health-related bioactive components in barley (Manach et al., 2004).
Barley is a seasonal crop which can grow in a wide range of environmental conditions including arid, semi-arid and wet climates. Barley is well known as an excellent choice for diet fortification in deficient protein areas (Sarac and Henry, 1998). Barley (Hordeum vulgare L.) is an important cereal grain ranking fourth in the world (FAO, 2007) with almost all of it being used by the malting and brewing industry and as an animal feed. Today, it is considered a healthy and functional grain and an excellent source of β-glucan, B-complex vitamins, minerals (especially P, K, Ca, Mg and Se), tocotrienols and tocopheols. Moreover, there are many classes of phenolic compounds in barley, such as benzoic and cinnamic acid derivatives, proanthocyanidins, quinones, flavonols, chalcones, flavones, flavanones and amino phenolic compounds (Sharma and Gujral, 2010).
Unfortunately, at present very little barley is utilised as human food because of its hulled nature, difficulties in milling and lack of gluten proteins (Lazaridou et al., 2003). However, the incorporation of barley flour or the use of whole grain flour (usually from wheat) or bran all diminish bread quality, particularly loaf volume, of wheat composite breads (Gill et al., 2002) This deteriorating effect has been shown to be more than solely the dilution of wheat gluten. Fibre, especially insoluble fibre, may mechanically interfere with gluten network formation (Gill et al., 2002) and cause rupture of gas cells (Courtin and Delcour, 2002). Both soluble and insoluble fibres, tightly bind high amounts of water, which may make it less available for the development of the gluten network and may further result in less steam production during baking (Gill et al., 2002).
Over the last two decades, the use of sourdough techniques to improve the baking properties and sensory characteristics of breads manufactured with barley flour has been explored. Sourdough fermentation is one of the oldest biotechnological processes, dating back to ancient Egypt, where both beer and bread were produced by the help of yeasts and lactic acid bacteria. Spontaneous fermentation must have been used in the very early days, just activating the naturally occurring microbes in milled grains (Arendt et al., 2007).
Sourdough was used as a leavening agent in bread production until it was replaced by baker’s yeast in the nineteenth century; from then on its use was reduced to artisan and rye bread. In modern baking, leavening of bread dough is accomplished by the addition of baker’s yeast into bread dough. Even though sourdough process is challenging technologically since the longer fermentation process prevents high output in bread production, today an increasing number of consumers are interested in bread made without baker’s yeast.
The interest in barley has increased due to its many beneficial constituents, and there is a desire to increase the amount of barley in the human diet. This can be achieved by incorporating barley in bread formulas.
Therefore, the aim of the present work was to study the use of sourdough for enhancing the nutritional value, texture and sensory characteristics of some bakery products made of wheat fortified with barley flours. The aim was achieved through the following points:
1- Collections materials: - wheat flour 82% and barley flours, chemicals for baking, starter culture for sourdough.
2- Determination the proximate composition of wheat and barley flour.
3- Determination the contents minerals, phytic acid and phenolic compounds of wheat and barley flour.
4- To study the effect of wheat flour replacement with barley flour on dough and bread characteristics.
5- To study the effect of using sourdough on rheological characteristic of dough made of wheat flour blended with barley flour.
6- To study the effect of sourdough on bread characteristics.
7- To study the effect of sourdough on pH and total titratable acidity of dough and bread.
8- To study the effect of sourdough on the free, bound and total phenolic compounds in bread.
9- To study the effect of sourdough on antioxidant activity.
10- To study the effect of sourdough on sensory properties of both balady and pan bread loaves.