Yummy Yoghurt Makers

Yummy Yoghurt Makers Organiser’s Card About the activity This activity is designed to get children thinking about reversible and irreversible reactions. The children have been sent an email by Mita Gabbar on behalf of Practical Action, who help farmers turn milk into yoghurt in rural Bangladesh in order to make the most money. Can the students help to find the most delicious flavour? Through this activity you will support your group to: • Make different varieties of yoghurt • Conduct a taste test scientifically • Record and present their results to the group • Think about the lives of those living in a developing country` Kit list • Different types of milk (full fat cow’s milk, skimmed and/or semi-skimmed cow’s milk, goat’s milk, sheep’s milk, soya milk, almond milk, etc). • Flasks • Saucepans • Cooker, hot plate or some other source of heat • Large spoons for stirring • Small spoons for tasting • Yoghurt (make sure it is ‘live’ yoghurt) • Dried milk powder (if using) • Ready-made yoghurt samples, prepared the day before • Blindfolds made from pieces of fabric • Thermometer • Selection of finely chopped or pureed fruit What to do 1. Prepare a selection of yoghurt samples the day before this activity so that children can test them. Remember to use a variety of milks. 2. Introduce the activity using the email from Mita. Children may be surprised that in other countries children don’t always go to school. Tell them how people around the world are trying to change this as one of the Global Goals. For information go to globalgoals.org/global-goals/quality-education/ 3. Give out activity cards and equipment to the children. 4. Encourage children to discuss their ideas and how they will use the resources to carry out their investigations. 5. Encourage the children to predict the type of yoghurt the different milks will make. Will the yoghurt be thick, runny, sweet or sour?

6. Help the children to make their own batches of yoghurt using different ingredients. Make sure you have a ready-made yoghurt sample for each of the types of milk the children will be using to make their own yoghurt. 7. Support children to conduct their investigation and make their own records of their results. Allow the children to do blind taste tests of the ready-made yoghurt samples. Can they guess which milk was used to make each yoghurt sample? Were their predictions right? Children can vote for their favourite yoghurt. Can they make it even tastier by adding chopped or pureed fruit? 8. Ask the children to present their findings to the rest of the group, they can be as creative in their presentation as they want e.g. they could make a pictogram of each person’s vote to show which yoghurt was the most popular. They could write to Mita to tell her what they found out about making yoghurt and to share their recipes. Things to think about To make 500ml of yoghurt you will need 500ml of any milk and 3 tablespoons of fresh, live, plain yoghurt. Using 25g of dried milk powder for every 500ml of milk will help your yoghurt set. Some types of milk take longer to set. Heat the milk in a saucepan. When the milk reaches 46°C take it off the heat and stir in the yoghurt. The temperature of the milk is important. Help the children measure the temperature of the milk carefully. Pour the mixture into a flask and leave overnight. In the morning it should have thickened and turned into yoghurt. Making yoghurt is an irreversible reaction. Once the bacteria have fermented the milk you cannot turn it back into milk. This activity it a good opportunity to think about which reactions they know that are reversible, for example turning water into ice. Keywords • Yoghurt • Cultures • Fermentation • Reactions Watch out! Emphasise washing hands and keeping work spaces and equipment clean when preparing food. Ensure adult supervision when children make the yoghurt. Check for any food allergies. Find out more In developing countries like Bangladesh, education is especially important. However, with no national provision, families have to pay to send their children to school. Making and selling yoghurt is one way that families can generate an income for school fees. To help pupils find out more about the lives of children in Bangladesh take a look at some of Practical Action’s other activities for Primary including the Floating Garden Challenge, an investigation into growing food in areas of Bangladesh prone to flooding. practicalaction.org/primary British Science Association Registered Charity No. 212479 and SC039236