Cereal fermentation by yeast Date: Bread making by fermentation is an ancient process. Yeast, the most common one being S. cerevisiae, is used in baking as a leavening agent, where it converts the fermentable sugars present in the dough into carbon dioxide. This causes the dough to expand or rise as gas forms pockets or bubbles. When the dough is baked, the yeast dies and the air pockets "set", giving the baked product a soft and spongy texture. Most yeasts used in baking are of the same species common in alcoholic fermentation. In addition, Saccharomyces exiguus (also known as S. minor), a wild yeast found on plants, fruits, and grains, is occasionally used for baking. In bread making, the yeast initially respires aerobically, producing carbon dioxide and water. When the oxygen is depleted, anaerobic respiration begins, producing ethanol as a waste product; however, this evaporates during baking. When yeast is used for making bread, it is mixed with flour, salt, and warm water or milk. The dough is kneaded until it is smooth and then left to rise, sometimes until it has doubled in size. Some bread doughs knocked back after one rising and left to rise again by kneading. Longer rising time gives better flavor, but if it is left for too long initially, the yeast can fail to raise the bread in the final stages. The dough is then shaped into loaves, left to rise until it is to the correct size, and then baked. Bread can be prepared by three methods 1. Straight dough method (mix all ingredients at a time) 2. Salt delay method (mix all ingredients except salt which is added later) 3. Spongy & dough method (mix sugar + maida keep it overnight and then add other ingredients) Objective: To prepare the leavened dough (bread) from wheat flour using baker‟s yeast. Materials required: Wheat flour Dehydrated yeast Salt Sugar Fat Ca propionate Water - 1 kg - 30g - 15g - 200g - 30g -5g - 500-600 ml Procedure:          Mix wheat flour + yeast + sugar+ fat+ Ca propionate and salt(finally) and prepare the dough Knead the dough till it becomes soft and elastic Cover the dough and allow for fermentation for about 20 min. Divide the dough into 400g pieces Round the dough pieces and keep for intermediate proofing for about 5 min Stretch each piece as long as the size of bread tin, fold them over three times and keep the dough for molding Place the molded dough piece in the greased bread tins (Panning / Proofing) Bake @ 200C for 30 min Cool for 2 hrs and pack. Observation: Review Questions 1. What is the role of Ca propionate in bread making? 2. What is the other name for Saccharomyces cerevisiae? 3. Define Kneading and Panning. 4. What is the actual process involved in bread making or wheat flour fermentation?