The Cosmos Big Food Quiz

Cosmos Magazine


Cosmos is a quarterly science magazine. We aim to inspire curiosity in ‘The Science of Everything’ and make the world of science accessible to everyone.

By Cosmos

This year’s school theme for National Science Week is Food: Different by Design. To celebrate, here is our Cosmos Big Food Quiz! How many can you get right?

1. Which of these is not a nut: Coconut, peanut or cashew?

Trick question – none of them are nuts.

Nuts are tree fruit that have a hard shell protecting a kernel. Nutshells don’t open by themselves, so the seed kernel inside will only be available if the shell is cracked open, rots or is digested. Chestnuts and acorns are both nuts.

The whole coconut fruit is huge and green – the part we see at the shops is actually the inside of the fruit. It is a type of fruit called a drupe, which has a hard seed inside flesh, like a peach.

The coconut’s flesh is fibrous and a lighter brown, and the dark-brown woody sphere in the centre is the seed – similar to a peach seed.

Peanuts don’t grow on trees – they grow in the ground. They are legumes and are cousins of beans and peas.

Cashews grow on the end of fleshy stalks called cashew apples – this part is actually swollen stalk, not an apple at all! They have a tangy and sometimes sour flavour, but can be turned into juice.

The cashew that grows on the end is the real fruit, but we take this bit off and eat the seeds inside because the fruit has too many toxins.

These ‘nuts’ have similar nutritional properties to real nuts, so it is okay to call them nuts, with this in mind.

2. Cochineal is a very common food dye used in Tim Tams. It is popular because of its ‘natural’ origin and red colour. Where does it come from?

Pulverised female Dactylopius coccus beetles! These parasites are native to tropical and subtropical South and North America, where they live on cacti such as the prickly pear.

They produce carminic acid, which deters other insects from eating them. When this acid is mixed with aluminium or calcium salts, it makes cochineal, a reddish dye.

In the late 18th century, the beetles were brought to Australia in prickly pears, in order to start Australia farms. The beetles all died, but the prickly pears grew so well they ended up invading large areas of New South Wales and beyond. That’s why it is common to see prickly pears growing around the state.

3. Can you buy clones in the supermarket?

Almost certainly – because almost all the fruit you buy are clones.

Cloning means the offspring is exactly the same, genetically, as the parent. If you take a cutting from a plant and put it in soil or water, it may grow some roots and become its own plant. This form of propagation doesn’t require sexual reproduction, so the offspring – the cutting – is a clone of the original plant.

Cloning crops via rooting, grafting or budding keeps our fruit consistently tasty – if you plant apple seeds, they probably won’t be as sweet and juicy as their parent.

Bananas need to be cloned because they are usually grown to have no seeds, so new banana trees are mostly grown from cuttings.

4. Which of these do we eat the most of: grass, trees, or legumes?

We eat all these things, but grasses are the most common staple food in the world. Most of the grains we eat are types of grasses that have been bred by farmers to produce lots of seeds. Rice, wheat, barely and millet are all grasses and are the most widespread staple foods.

Legumes such as soybeans and other peas are also very common in some parts of the world, because they are quick to grow and nutritious.

Trees give us lots of fruit to eat, but it is much harder to store fruit than grains and beans. They are still a very important part of the diet, though.

5. Is your fish dinner basic or acidic?

Basic. The molecules that make fish smell ‘fishy’ are called amines, and they have a pH of around 9.5 to 11. This is why vinegar and lemon taste so good with fish – they are acids that neutralise the amines.

Want to try another quiz? The Cosmos Big Olympic Quiz

6. What are the dots on the outside of a strawberry?

Fruits! They may look like seeds, but the seeds are actually inside the little hard fruits.

The big red bit is swollen stem material – called an accessory fruit – on which the real fruit grow. Farmers have bred the accessory fruits to be big, sweet and red, so we can have a tasty snack.

The strawberries we find in the supermarket don’t appear in the wild at all. Instead, they were created by hybridisation – breeding two different plants – of two separate rose species.

7. Would you expect your tea to look darker in Adelaide or Sydney?

Probably Adelaide, because its water is slightly more basic than Sydney’s water, although this changes from suburb to suburb. Acid breaks down tannins, which are responsible for the colour of tea.

Incidentally, this is also why tea with a dash of lemon is lighter.

8. Which two of these are related? Potatoes, tomatoes and sweet potatoes.

Potatoes and tomatoes are both part of the genus solanum, which are nightshades! That’s right – if you eat the wrong parts, they are poisonous.

Tomatoes and potatoes look completely different because the tomato is the berry of the plant, and the potato is a root tuber. Their plants, though not the same species, do look quite similar, and potato plants grow small, green, tomato-like berries that are poisonous.

Tomatoes and potatoes are also related to chillies, capsicums and eggplants, but they have all been bred to have particular traits and flavours. They were all once very similar and shared a common ancestor in South America, but over many years of selective breeding, they became quite different.

Tomatoes and potatoes are so similar that a company called Thompson and Morgan grafted them together and made a TomTato – a plant with potatoes on the bottom and tomatoes on the top!

Sweet potatoes are part of a family of flowers called morning glory.

9. How is bread kept fresh in Australia?

Supermarket bread is treated with vinegar and sealed in bags that are filled with carbon dioxide, so microbes can’t reproduce. It also means you can keep the bread out of the fridge, so it stays soft, but microbe free.

You can refrigerate bread to stop microbes from growing, but the bread will become stale faster. This is because bread becomes fluffy when long chains of starch molecules – called amyloses – break apart during fermentation. When the bread is sitting out, the molecules reform, and it becomes stale.

This process happens faster in the fridge.

10. Why is corned beef shiny?

Roast beef and pastrami sometimes have an iridescent sheen to them because of diffraction.

When cured meat is cut, it is sliced ‘against the grain’ and the resulting slice has bundles of fibres that are evenly spaced. When light hits this, it experiences diffraction, where the waves hit an obstacle and bend.

As the white light hits the nooks and crannies of the meat fibres, the waves bend in different directions and are separated into a spectrum of colours.

Sometimes, thin layers of oil in the cured meat can enhance this phenomenon, which is why it shows up more often in cured meats.

It is perfectly safe to eat iridescent meat.

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