Introduction: Does anyone know where milk comes from? What do cows eat?
Grass is quite tricky to digest, people can’t digest it at all. Do you know how cows manage?
Cows have four stomachs (give out colouring sheets), start ‘stick the stomach on the cow’.
I drew a cow on a big sheet of paper and four stomachs on coloured paper. Then I blindfolded the children and got them to try and stick the stomachs in place.
As we played, I talked about what the stomachs are used for.
This big one: the rumen, contains special tiny creatures (microbes) that can break down grass into sugars that the cow can digest. Cows also chew things twice, how do you think they do that?
It’s called rumination. The cow chews grass into big balls then swallows it into its stomach, in the rumen, the microbes begin to break it down, then the cow regurgitates (pushing the food up with the reticulum – another one of those ‘stomachs’) so that it can chew the grass again to continue breaking it down, any small pieces sink to the bottom of the rumen, where the omasum acts like a big filter, making sure that only nutrients that have been broken down continues on to the, the abomasum (which – quite sensibly – is beyond the omasum). The abomasum is much like our stomachs, what do you think it does?
It breaks down food using various acids and enzymes, so that the nutrients can be absorbed by the body. Cows are the same family of animal as us, since we both make milk for our young, do you know what family that is? Cows and people are both mammals.
Does anyone know where butter comes from? Today we are going to turn cream into butter.
Individual Task: Jars should be one third filled with cream, sealed tightly, then shaken for about twenty minutes. Butter must be washed with cold water to stop it going sour. We drain the butter through clean hankies, then press it against the sides of our bowls to squash out the buttermilk.
Gather together for a conclusion: Can we taste the difference between olive oil spread (or some other weird butter replacement – I never buy any ‘butter alternatives’, so I had to ask a friend to bring some), salted butter and our butter?
What happens if you try to mix oil and water? The oil floats to the top of the water and sits there.
What about if we add washing up liquid, does anyone know what happens then?
The washing-up liquid helps the oil to mix in with the water, and we’ve made an emulsion.
Milk is a kind of emulsion where droplets of fat are suspended in water.
Butter is another kind of emulsion where droplets of water are suspended in fat.
Break for drink and snack and a story about cows.
Active Science: Act out how an emulsifier works, getting children to hold on to a yellow tub with one hand and a blue block with the other (hopefully we’ll get the right flower shape). It worked pretty well 😉
Optional extension: Add some vinegar or lemon juice to warm milk and watch it curdle, then strain through a clean hanky – this is curds and whey (like Little Miss Muffet had), rinse the curds before eating.
The children were very wary about tasting this, but, actually, it wasn’t too bad.