Asked by Peter Bettings

The origin of stomach rumblings comes from muscle contractions and fluctuation. As food enters the gastrointestinal tract its walls squeeze the contents through the system at regular intervals to clear any potential buildup of food, gases and liquids. This fluctuation is known as the basic electrical rhythm (BER). The speed and force of the muscle fluctuations increases both in the presence of foodstuffs and also without them. In this latter case, the nerve receptors initiate a reflex generation of electrical activity, causing the muscles to contract and vibrate (ie rumble).

1. Tasty – In certain Asian cultures the swim bladders of large ocean fish are considered a tasty foodstuff, renowned as a delicacy that is commonly served braised.

2. Origin – Charles Darwin wrote: “There is no reason to doubt the swim bladder has been converted into lungs [and that] all vertebrates with true lungs are descended from an ancient prototype.”

3. Hearing – In some fish the swim bladder is connected to the labyrinth of the inner ear by a bony structure from the vertebrae. This provides a precise sense of water pressure and hearing.

4. Gas – The mix of gases in swim bladders varies. Shallowwater fish bladders tend to approximate that of Earth’s atmosphere, while deep-sea fish have higher oxygen mixes.

5. Bladder-free – Cartilaginous fish like sharks lack both lungs and swim bladders. This has led to postulation that both these organs developed 420 million years ago after such species divided from other fish.

Asked by Stephen Blaze

Taste buds are sensory organs that are found in the little bumps (or papillae) on the tongue. The tongue contains about 8,000 taste buds and they’re replaced approximately every two weeks. Sensitive microscopic hairs on the taste buds (microvilli) pick up dissolved chemicals from food and send electrical signals to the brain that distinguishes between five different tastes: sweet, bitter, savoury (umami), salty and sour. Varying sensitivity to these tastes occurs across the whole of the tongue. But taste buds alone cannot tell us the exact flavour of food. Other factors such as smell, spiciness, temperature and texture also contribute to the eventual taste. So if you hold your nose while you eat then your brain won’t get the full taste story!

Scout Davies, Science Museum

Jelly is a soft semisolid containing gelatine (or gelatin). Gelatine is processed from the protein collagen found in skin and bones, so we wouldn’t advise eating jelly if you’re a vegetarian. The molecules in gelatine are intertwined in a triple helix. As they are mixed with hot water their bonds break, unravelling and becoming long stretchy wiggly lines. As the water cools down, the helices start to reform and cross-linking occurs. This creates supermolecules that are so long they span across the whole jelly in a three-dimensional web, and water gets trapped in the spaces giving jelly its wobble.

Dwaine Anthony Clarke, Science Museum

Artificial flavourings are used to improve the taste of food or to chemically re-create a flavour that cannot be achieved through conventional production. Artificial flavours can be produced cheaper than their natural counterparts and they can also be so concentrated that much less of them is required to generate the same taste, making them very cost-effective.

To chemically re-create the taste of a naturally occurring flavour, specialist flavour chefs first obtain the essential chemicals from the foodstuff they’re trying to emulate. These chemicals are leeched out of the food through either boiling, roasting or some other refining process. This leaves a concentrate (the natural flavouring), which can be further vaporised or liquefied to obtain an even more concentrated version.

By looking at the substance through a chromatograph (an instrument that enables the separation of complex mixtures) flavour scientists can establish how the molecules in the concentrate are arranged, and then replicate the chemicals to create a man-made equivalent of the original flavour. Differing combinations of the same molecules can lead to a whole host of different flavours.

Asked by Kim Bridges

Meat can harbour many different bacteria, viruses and even parasites. Cooking meat properly destroys them, making meat much safer for consumption. Bacteria and viruses can easily make you ill, while parasites can grow inside your gut and even migrate to your brain. Food poisoning is a very serious business and by not cooking meat thoroughly, you are greatly increasing your chances of getting something nasty. People quite often eat raw meat such as steak tartare, but it requires extra care in the preparation.

Besides safety, cooking meat also makes it taste better, not to mention easier to chew and digest. By cooking meat and other foods, humans can get much more energy than from chewing on raw food alone.

José Monteiro, Science Museum Explainer

Yes. Oversleeping can cause headaches because you’ve slept too long without food and water. This is because headaches can be triggered by dehydration and low blood sugar. Depression and other undiagnosed medical problems can cause people to sleep more than average. This may be why studies find that people who sleep more than seven to eight hours have a shorter life expectancy. How much sleep we need varies among individuals and also varies over a lifetime. As babies we need more sleep than when we’re older.

Olivia Harwood, Science Museum

Palm oil is used in many food and cosmetic products and has been championed as a source of green sustainable fuel. It is a huge part of the export revenue for countries such as Indonesia and Malaysia. However, there is significant concern worldwide about its sustainable credentials.

The massive expansion of oil palm over tropical forest and bog land has had significant impacts both on large species such as orangutans as well as countless other species of tropical plants, invertebrates, birds, mammals and reptiles by destroying large tracts of natural habitat. The growth of the plantation economy also impacts heavily on local communities which traditionally relied on forest resources and who do not necessarily benefit from industrial government-driven schemes.

Moreover, its cradle-to-grave credential as a ‘green’ fuel is very questionable, and many researchers believe that the standing forest which the plantations replace are important carbon sinks, so that overall – given the high production, processing and transport costs of the oil – retaining the forest and continuing to use fossil fuel might be more effective in reducing carbon emissions, at least in the short-term anyway.

Dr Robert Bloomfield, IYB-UK/Natural History Museum, London