Rheological properties


Lesson 7:Different Rheological Properties; Application In Bakery
And Confectionery

Rheological properties

Understanding the rheological properties of dough and batter used in preparation of bakery foods helps to develop better products because the physical properties are associated with recipe formulation and processing stages ultimately influencing the product quality.

Doughis a paste made out of anygrain flour by mixingwith water. This process is an essential step in food processing and also in baked foods. Batteris a semi-liquid mixture of one or moreflourscombined with liquids such as water,milkoreggsused to prepare various bakery foods. Theviscosityof batter may range from very "stiff" (adhering to a spoon turned upside down) to "thin" (which can be poured or dropped from a spoon and sometimes called "drop batter"). Heat sets the batter into a solid form. Batters may be sweet orsavory, with added sugar, salt or both. Many other flavorings such asherbs,spices,fruitsorvegetablesmay be added to the mixture according to the recipe. Cakes, pancakes, puddings, pakodas, dosa, idli etc are made from batters. Some types of biscuitsandcookiescan also be made with batter.

Baking involves a process of exposing the batter and dough to heat in controlled conditions in oven which leads to production and expansion of gas, coagulation of gluten and other proteins, gelatinization of starch, evaporation of water and colour formation on the crust of the baked product. The net effect is an increase in volume and development of rigidity. Elasticity and extensibility increase with the rise in temperature. Evaporation of moisture renders the product crisp. Browning reaction of sugar and protein and caramelization of sugar facilitate colour change.

Quick breads such as biscuits, muffins, popovers, waffles are flour products that are baked immediately after mixing of the ingredients. The basic ingredients are flour, liquid, salt, sugar, fat, leavening agent and egg. Micro organisms are not used for leavening. The ingredients in biscuits include flour, milk, fat, baking powder and salt. The dry ingredients are mixed and sifted together, fat is cut into flour mixture, to which liquid is then added to make dough. It is then rolled, cut and baked

Muffins are made from a drop batter of two parts flour to one of liquid. The batter is poured into oiled cups and baked until a thin golden-brown crust appears. Popovers are made from the thinnest of all batters prepared with equal parts of flour and liquid. The proportion of liquid is so great that the gluten particles tend to separate and float on the liquid rather than to form the elastic strands. Therefore, eggs are added to provide extensible proteins that supplement gluten. The ingredients are mixed and are beaten until smooth. The batter is poured in oiled and preheated pans and baked until the crust is firm. The final product is crisp, brown, thin-walled, and large.

Cake batters are of the drop batter consistency. The ingredients are flour, eggs, milk, salt and sugar. The combined weight of eggs and milk should equal the weight of the flour or sugar. Eggs contribute to the structure of the cake and egg yolk emulsifies the shortenings in the batter. Butter is the most common shortening used. Shortenings serve to tenderize the gluten. Unshortened cakes (sponge cakes) such as angel cake, yellow sponge cake, and mock sponge cake depend on air or steam for leavening. These cakes are light and fluffy, with fine crumb, thin-walled elongated air cells which are evenly distributed throughout. Ingredients are egg white, sugar, flour, salt, flavoring and cream of tartar. Liquid and baking powder may be substituted for half the total egg ingredient.

The batters similar to cake batters and doughs are used in preparation of cookies/ biscuits. Lesser amount of liquid, more fat and egg, render the cookies crisp. Sheet cookies are made from drop batters spread out as a thin layer on greased pan, cut into desired shapes after baking. Drop cookies are prepared by dropping spoonfuls of batter onto a greased pan and baked. Rolled cookies are made from stiff dough that is chilled and rolled out thin and cut into shapes and baked in greased pans. Refrigerated cookies have more fat and the dough is molded and chilled until firm enough to be sliced and baked on ungreased baking sheets.

Last modified: Tuesday, 6 December 2011, 5:51 AM