Design dough investigation

Transcription

1 Design dough investigation

2 Yeast x 400 Cell wall nucleus Yeast is a single celled organism. Yeast is a fungus, which means that yeast cells are examples of plant cells. Yeast cells can use a variety of food sources any kind of sugar is a suitable energy source. Yeasts exist naturally and can be seen as the white cloudy covering most easily seen on purple grapes or plums.

3 Yeast x 400 New cell budding off scars where new cell has budded off Yeast can multiply very quickly in suitable conditions and with a suitable food source. They can reproduce by binary fission (splitting in two) or by budding. In budding yeast, new cells form from the side of parent cells. The nucleus then divides and one new nucleus moves into the new cell. The new cell then pinches off from the parent.

4 Since yeast is a living organism, it must carry out respiration to release the energy it needs from food. If oxygen is present, it will carry out aerobic respiration making use of the oxygen in air to help the release of energy from the food. Glucose + oxygen -> carbon dioxide + water +ENERGY Anaerobic respiration in yeast is also known as fermentation.

5 There are two products from fermentation in yeast which have been used for centuries by man in production processes Glucose -> ethanol (alcohol) + carbon dioxide + Energy Yeast can therefore be used to produce alcohol. This is how alcohol is produced in wine making and beer making.

6 The yeast feeds on sugar in the flour and starts to respire. Since the yeast in in the middle of a big lump, most of the respiration is anaerobic. When you cut bread through, it is full of tiny holes. These holes are air bubbles in the bread. To make bread, you start with a dough. The dough is a mixture of flour, yeast and water.

7 CO 2 alcohol The bread that this dough would make would be very tough and heavy. If the dough is allowed to sit for a while, the yeast starts to respire and produce new products Glucose -> CO 2 + alcohol + energy The CO 2 +is the bubbles in the dough, and increases the volume of the dough. It doubles in size The dough is left in a warm place to encourage the yeast to grow.

8 Bread Making Put 700g flour into mixing bowl Add 1 level tablespoon of yeast, salt and sugar Mix thoroughly Add 425 ml water Mix with spoon, then knead by hand for 3 10 minutes Leave dough covered in the bowl to rise. (1-2 hours) Knock back the dough and knead again for 2-5 min Split the dough into 2 x 1 lb loaf tins Bake at gas mark 8 for min

9 Construct a table to show ingredients Flour Yeast Sugar Salt purpose Describe how you make dough rise and what conditions this takes place in Explain why you do not get drunk when you eat bread, though alcohol is made by the yeast during fermentation

10 Target - Design dough investigation Rising dough investigation Dough is a mixture of flour, sugar, yeast and water. Your task is to design an investigation to find out either How does temperature affect how quickly the dough rises Or How does the weight of sugar affect how quickly the dough rises

11 The basic dough mix is 8 g flour and 5 ml yeast suspension (yeast mixed with water). If you need to make it runnier, add water. To this, you add up to 1g sugar. (unless sugar is what you are changing!) Make this up in a beaker and split between your test tubes. Fill about 1/3 of the boiling tube to allow room to rise.

12 Aim I aim to find out how... changes how quickly the dough rises. Method Step by step instructions Include all quantities In enough detail for someone to repeat your experiment A statement of all the things you kept the same in the experiment A statement of how long your experiment will be left for A description of what observations or measurements you will take to get your results. Results A table and a graph to show the results of the experiment

13 Effect of temperature on how quickly dough rises

14 Effect of weight of sugar on quickly dough rises 0g 0.3g 0.5g 0.7g 1.0g