Yeast-Leavened Wheat Breads

Table I. Comparison of the Important Neutral/Basic Volatile Crust Flavor Compounds of a Chemically Leavened Wheat Bread (CL—WB)a With Those of a Yeast-leavened Wheat Bread (YL-WB)b ...

Whole wheat items. Whole hard wheats are used for yeast-leavened whole breads, whereas whole soft wheats are used for various types of cookies. The intermediate protein whole wheat flour is used for whole wheat crackers and flour tortillas. 

To gain an insight into the origin of the Acp in wheat bread crust, two different experiments were carried out. First, the formation of crust odorants from yeast and from chemically leavened doughs was compared and, secondly, model experiments on the formation of the Acp were undertaken. 

The flavor compounds of the crust from the chemically leavened model bread were then compared to those recently identified (6) in the crust of a standard wheat bread which was leavened by addition of yeast (Table I). One striking difference was that Acp (No. 16), which showed the highest FD-factor in the yeast-leavened bread showed a very low FD-factor in the chemically leavened bread. This indicated, that the flour contained only minor amounts of the precursor (s) for the formation of Acp. On the other hand, 2(E),4(E)-decadienal, 2(E),4(E)-nonadienal, l-octen-3-one and 2(Z)-nonenal, which are undoubtedly formed by a heat-induced oxidative degradation of the flour lipids, became predominant odorants in the chemically leavened compared to the yeast-leavened bread. 

Zinc deficiency has been found among peasant populations in rural areas of the Middle East. Unleavened whole wheat bread can account for 75% of the energy intake in these areas, that is, Iran, Egypt, and Turkey. This diet, which does not contain meat, does contain zinc, but it also contains phytic acid at a level of about 3 g/day. The phytic acid inhibits zinc absorption. The yeast used to leaven bread produces phosphatases that hydrolyze the phosphate groups from phytic acid. 

As a leaven for bread a mixed culture of Lactobacillus brevis TKK 105-6-1 and P. acidipropionici TKK 114-3-1 was used after three days of combined cultivation at 30 C in the medium containing hydrolyzed wheat flour, yeast extract and mineral salts (Javanainen et al., 1987) the pH of the culture was adjusted to 5.0-5.8 by adding calcium carbonate (20 g/1). Almost... 

Among the yeast- and bacteria-leavened products are the following (1) bagels—doughnut-shaped rolls (2) Danish pastry (3) Jewish challah bread (4) malt breads (5) pita or pocket bread (6) pizza (7) raised doughnuts (8) salt-rising bread (9) sourdough bread and (10) whole wheat bread. 

Yeast-leavened breads— Wheat flours rich in gluten are... 

Corn flour The smallest panicles of ground corn. Pancake mikes, as a filler In venous meat products, and as a substitute for wheat flour in baking. Doughs made from com Hour leek sufficient elasticity Ibecause of their low-gluten content for making yeast-leavened breads... 

Separation of flours into high-protein and low-protein fractions—In the past, high-protein hard wheats were used to make flours suitable for yeast-leavened doughs and low-protein soft wheats yielded flours for quick breads. Now, either type of wheat may be milled and separated into high- protein and low-protein fractions by swirling streams of air in a process called air classification. This procedure enables millers to produce flours to meet customers requirements. 

Wheat is the only cereal that possesses functional gluten. The flour, upon hydration and the mechanical work of mixing, forms a cohesive and elastic dough suited for production of yeast-leavened breads, chemical-leavened bakery goods, and pasta (Pomeranz 1988, Kulp and Ponte 2000, Owens 2001). Hard wheats are preferred for production of yeast-leavened breads, whereas soft wheats are used in the manufacture of chemically-leavened products such as muffins, cookies, and cakes. Durum wheats are almost exclusively used for the manufacture of long and short pasta products (Fabriani and Lintas 1988). 

The flour is used for the production of yeast-leavened donuts, wheat-flour tortillas, crackers/ saltines, oriental noodles, Chinese steamed bread, pretzels, soft pizza crusts, and gravies. It is also used to produce breakfast cereals, and snacks. 

Soft pretzels are produced following conventional baking procedures. The main difference is that shaped (e.g., bow ties) doughs are normally dipped in a sodium bicarbonate solution. This gives the outer layer a shiny brown color. Like other yeast-leavened breads, the best-quality soft pretzels are obtained from hard wheat flours. 

French bread Yeast-leavened breads produced from hard wheat flour, water, and salt that are baked into crusty loaves. The authentic French breads or baguettes do not contain sugar and shortening. Thus, these breads have a short textural shelf life and are considered dietetic bread. 

The next five chapters represent the core of the book becanse they thoroughly describe the processing of basically all types of cereal-based foods consumed by mankind. Chapter 10 covers bakery prodncts obtained from wheat, snch as different types of yeast-leavened breads, cookies, crackers, cakes, flonr tortillas, pasta, and noodles. Chapters 11 and 12 detail various industrial processes to manufacture... 

Manufacturing processes can result in a substantial loss of the vitamin for example, during the milling of whole wheat to white flour, 75% of the folate is lost (B8). Bread was found to contain more folate than the flour fixim which it was made and this was due to the effect of the added yeast. Folate deficiency has been found to be relatively uncommon in Iran and this prompted Russell (R8) to measure the folate content of various Iranian breads since bread is the staple food in that country. They found village wholemeal bread to have a free folate concentration of 340 M.g/kg and leavened breads made... 

Dough consisting only of flour and water gives a dense flat cake. Baked products with a porous crumb, such as bread, are obtained only after the dough is leavened. This is achieved for wheat dough by addition of yeast while, for fine baked products, baking powders are used. Rye dough... 

Yeast fermentation which occurs during the leavening of whole grain breads breaks down the phytates (poorly utilized phosphorus compounds in the bran of the wheat grain) that interfere with mineral absorptlon. Hence, there is better utilization of the minerals In such breads when yeast is used instead of baking powder. 

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