9.Dough+n+Bread+conditioners

__Dough and bread conditioners__ 1.Describe the development of gluten in bread during mixing process.

The major proteins of bread, gliadin and glutenin, can be viewed as coiled or folded chains, with the structure stabilized by bonds between sulfur atoms (disulfide bonds) on adjacent areas of the molecules (intramolecular bonds). Mixing stretches the molecules and breaks the relatively weak bonds. During resting, the disulfide bonds can re-form either within (as before) or between molecules (intermolecular). When bonds form between molecules, the resulting structure (gluten) is much stronger than the individual proteins. (Used with permission from //Breadmaking Technology//, by Wulf Doerry, 1995, American Institute of Baking, Manhattan, KS.) It is gluten that has the strength to physically entrap gas bubbles within the loaf, giving bread its desirable texture. Too little protein in the flour, or too little mixing, results in a weak and sticky dough that is easily stretched, but does not retain much gas. Likewise, dough can be overworked, resulting in few intramolecular bonds, and a dough that is strong, but inelastic. Mixing time and energy is thus both a critical and time-consuming part of the bread-making process. Speeding up the dough processing time offers economic advantages - with less dough in process, the baker needs less and smaller equipment, less floor space and less labor. "No time" dough processes, which require little or no resting, are a common goal. Some processes use high-speed, high-energy mixing to speed up the gluten development. Dough conditioners can offer similar results with more traditional equipment. Often dough conditioners and high-speed mixing are combined.

2.What is the function of oxidizers in bread?

Oxidizers were originally thought to inhibit the action of proteolytic enzymes that could weaken gluten. The mechanism of dough strengthening by oxidizers has been found, however, to be quite different. In addition to disulfide bonding, which strengthens gluten, sulfur atoms on the protein molecules can bind with hydrogen atoms. Sulfur bound to hydrogen cannot form a disulfide linkage. Oxidizers "strip" hydrogen atoms from the sulfur-hydrogen (sulfhydryl) linkages, and make more sulfur available for the gluten-strengthening disulfide bond. Early oxidizers such as potassium bromate and iodate are effective, but less in favor today, as a small amount can remain in the bread. The bromate and iodate residues are considered potential carcinogens. More commonly used oxidizers today are azodicarbonamide (ADA), which can be used at up to 45 ppm in the United States, and L-ascorbic acid (LAA), or vitamin C, for which there is no usage limit in the United States. ADA works very quickly, and can easily be overused, producing dry dough that is hard to work, low volume and cracked bread surfaces. LAA works slowly; moderate overuse has no deleterious effect on quality and it is commonly used at about 75 ppm. LAA is currently the only oxidizing agent permitted in the European baking industry.