Читать книгу Food Chemistry - Группа авторов - Страница 78

They are also called improver or flour improving agent as they improve the baking functionality of flour. These agents are of following four types:

 a. oxidizing and reducing agent

 b. enzymes

 c. bleaching agents

 d. emulsifier

These agents are used to speed up the process of dough rising and also to expand the strength of dough.

 a. Oxidizing and reducing agents: Aging of flour occurs naturally when it is exposed to atmosphere. The oxidizing agents affect the sulfur-containing amino acids and aid to form disulfide bridges between the gluten molecules. The dough becomes stronger with the addition of these compounds. Examples of oxidizing agent include dehydroascorbic acid and potassium bromate, and they particularly oxidize the glutathione molecule. Potassium bromate acts directly and number of conversion steps are also less.Reducing agents make the flour weak by breaking the protein network. Benefits of the addition of reducing agents are reduction in mixing time, dough elasticity, proofing time, and improved machinability. Examples of reducing agent include cysteine and bisulfite.

 b. Enzymes: Different enzymes are used to improve the processing characteristics of dough. Examples of enzymes that are added for this purpose includes the following• Amylases: It breaks down the starch into simple sugars. Yeast uses it up and can ferment quickly. Malt is used as it is the natural amylase source.• Proteases: It improves the extensibility of dough by breaking the gluten.• Lipoxygenase: It is used to oxidize flour.

 c. Bleaching agents: Objective of addition of this additive is to make the flour whiter. Nitrogen dioxide is used for that purpose. In presence of high voltage, it is converted to nitrogen tetra oxide which is effective bleaching agent. Benzoyl peroxide is also used and it is better than nitrogen dioxide.

 d. Emulsifier: Lecithin, monoglyceride, and diglyceride are used as emulsifier to disperse fat evenly through the dough that helps to trap carbon dioxide more. Addition of emulsifier produces softer crumb and fine grain with increased baked volume.