Want to know what you're really eating? Look a little closer, and you'll find that food and drink manufacturers can use some pretty bizarre methods to enhance the flavour, preserve the texture or extend the shelf life of their products. Here are some of the strangest and most unexpected ingredients you'll find lurking in everyday foods. Be warned – some of them might make you lose your appetite...

Click or scroll through our gallery to discover the creepy ingredients lurking inside your favourite foods – counting down to the most off-putting of them all.

Many cheeses, including Parmesan, are made with rennet – an enzyme taken from the stomach lining of calves. This naturally occurring enzyme helps with digestion and milk absorption, and it's completely safe. However, many manufacturers now use vegetable or microbial (bacterial) rennet instead, as they're not only cheaper, but they're also vegetarian friendly. Products labelled as being rennet-free are also suitable for vegetarians.

Lea & Perrins Worcestershire sauce is a much-loved ingredient in kitchens all over the world. But how did it come to be? The story goes that chemist duo Lea and Perrins were trying to recreate a sauce that a nobleman had tasted in India; however, when their creation turned out to be completely unpalatable, it was left in a cellar. A year and a half later, the pair discovered that the sauce had matured into a delicious condiment. Today, Worcestershire sauce is still made just as it was almost 200 years ago – with the process involving packing anchovies in salt, then leaving them to mature for 18 months. 

If you cut up an apple, you’d expect it to go brown pretty quickly – that is, unless it had been treated with NatureSeal. A blend of vitamins and minerals (including citric acid), NatureSeal was originally developed to be used on cut apples and pears to prevent oxidisation and browning. Today, it's used on more than 30 varieties of fruits and vegetables across 30 different countries, and it's available to use at home as well. The company's website says that NatureSeal helps to 'maintain the natural texture and colour of fresh-cut produce for up to 21 days'.

Many processed foods contain a long list of food colourings made from a by-product of the petroleum industry – one of which is Yellow No. 5 (also known as E102 or tartrazine), a synthetic additive that used to give boxed mac 'n' cheese that distinct yellow colour. Tartrazine was linked to childhood hyperactivity in 2007, resulting in an EU requirement to put a warning label on products containing the additive. While there's no such requirement in the US, Kraft dropped tartrazine from its mac 'n' cheese recipe in 2016; however, plenty of processed foods still contain it.

Injecting poultry with a saltwater solution – a process often referred to as plumping – has been a common food industry practice for decades. Manufacturers claim that it makes the meat juicier and improves the taste, but many people argue its main aim is to boost profits by increasing the overall weight of the chicken. Data gathered by Premier Foods Group revealed that in the US, consumers spend as much as $2 billion (£1.5 billion) every year just on the saltwater injected into chicken. Frustratingly, the US and the UK currently don't require the label to state whether poultry has been plumped. 

This surprising ingredient gives a smoky flavour and aroma to foods such as barbecue sauces, baked beans, hot dogs and beef jerky. It’s created by capturing the condensation produced when the smoke from burning wood or sawdust collides with cold air; the droplets containing the intense smoky aroma can then be used as an alternative to actual smoking. On labels you'll typically see liquid smoke labelled as smoke flavouring – it's what gives sauces like Heinz Classic Barbecue Sauce and Sweet Baby Rays Original Barbecue Sauce their signature depth of flavour.

Bags of salad or packaged meat might contain a little more than you bargained for. To get them ready for the supermarket, these products undergo a process called modified atmosphere packing (MAP), which sees them sealed with carbon monoxide to keep them from spoiling. Using carbon monoxide in the process is considered safe in the US, Australia and New Zealand. However, it's banned in Europe over concerns that it may cause rotten meat to appear fresh.

From its best-selling tacos to its Crunchwraps and chalupas, many of Taco Bell's menu items feature the chain's signature seasoned beef. In 2014, Yum! Brands, the company behind Taco Bell, revealed that the beef contains – among other ingredients like spices and texture-boosting additives – caramel colour and cocoa powder. The cocoa powder doesn't add any flavour, but rather helps the beef maintain its colour, while the caramel colour is actually caramelised sugar, a common food colouring used in foods like cereals and pancake syrup.

Banned in the US and Canada – but allowed in the EU and the UK as food additive E285 – borax is a mineral that can be found in everything from household laundry products to enamel glazes. In the food world, it's used to control acidity and assist in preservation, and it can often be found as a firming agent in supermarket noodle and rice ready meals. It's also commonly added to caviar to help to keep it fresh for longer and to improve its consistency and flavour.

White chocolate technically isn't even chocolate at all. Milk and dark chocolate are made from cocoa solids – cocoa beans that are removed from their pods, fermented, dried, roasted and cracked open – while white chocolate is made from a blend of cocoa butter, milk products, vanilla, sugar and lecithin, a fatty emulsifier. You might be wondering whether the presence of cocoa butter might be enough to consider it chocolate; however, real chocolate must contain cocoa solids or cocoa nibs.

That bag of shredded Cheddar or grated Parmesan in your fridge most likely contains cellulose (wood pulp) – a by-product of the wood industry that's used to prevent the cheese from clumping together. Although it's safe to consume, many companies use it as a cheap way to bulk up their products. There have been several high-profile cases in the US – in 2017, the company behind Castle Cheese was fined $500,000 (£360,174) for selling grated Parmesan that was actually a blend of cheap Cheddar and cellulose.

Seaweed is a popular ingredient found in many dishes across the Asian continent – but did you know that an extract made from seaweed is also used as a thickener and a stabiliser in many supermarket foods? The natural extract, known as carrageenan, is commonly added to dairy alternative products including soya, rice and almond milks. It's also used instead of gelatine in some plant-based jelly and ice cream products.

Surprisingly, bone char – a material derived from the bones of cattle – is widely used in the production of some sugars, to refine and bleach sugar cane so it becomes the white colour we're used to consuming. According to PETA, the use of bone char is strictly regulated in the EU and the US; only countries free of BSE (also known as mad cow disease) are allowed to sell bones to be used in the production of sugar. Thankfully, although the bone char does come into contact with sugar as it's made, it doesn’t end up in the final product.

Bromelain, the same enzyme that makes your tongue tingle when eating pineapple, is also used in the meat-processing industry to help tenderise the meat in sausages, among other products. It works by breaking down the collagen in the meat to make it more palatable. Bromelain is most commonly found in pineapples, but enzymes with similar features can also be extracted from papayas and figs.

You might be surprised to learn that bananas may not be totally free from animal products. Some non-organic bananas are sprayed with chitosan, a pesticide made from the shells of shrimp, lobsters and crabs. The substance is used to fight bacteria and prevent the fruit from ripening too soon – thereby extending its shelf life at the supermarket.

Antibiotics are routinely fed to livestock to protect against illnesses, but the use of antibiotics to promote growth in animals has been banned both in the EU and the US. However, there are still serious concerns over the close links between the over-use of antibiotics in animals and antimicrobial resistance. Data gathered in 2018 revealed that farm animals in the US receive five times more antibiotic medication than livestock in the UK – and it also showed that roughly three-quarters of the worldwide supply of antibiotics is used on animals rather than people, raising further concerns about the possible effects of antibiotic resistance.

Carmine is a red food colouring that's made by boiling the shells of cochineal bugs (a type of beetle) – and it's commonly used in foods like sweets, lollipops and dessert sauces. Although it's harmless to most, it can cause severe allergic reactions, so the US Food and Drug Administration (FDA) requires carmine to be labelled clearly on products. If you see carmine, cochineal extract or E120 on the label, you’re eating powdered bug. Not keen? Synthetic alternatives Red No. 2 and Red No. 40 are made from petroleum products, so they're not particularly appetising, either.

Many of us enjoy a range of baked pumpkin treats come autumn – but did you know that if you use the canned stuff, you might not be baking with pumpkin at all? One of the most popular brands in America, Libby's Pure Pumpkin, actually consists of Dickinson squash – a close relative of the butternut squash. But why can they sell it as '100% Pure Pumpkin'? Well, it's because the FDA allows it; its policy says that products made from 'golden-fleshed, sweet squash or mixtures of such squash and field pumpkin' can be sold as real pumpkin.

It's more surprising what isn't in truffle oil than what is. It's no secret that fresh truffles are pretty hard to come by and harvest, which makes them incredibly expensive – so it shouldn't really come as a surprise that most truffle oils have never been anywhere near a real truffle. If you've tasted fresh shaved truffles and foods containing real truffle oil, you'll know the flavour differs considerably. This is because most oils are infused with synthetically made ingredients, specifically 2,4-dithiapentane: an aromatic molecule that gives truffles their smell.

Sure, maggots aren't an 'ingredient', as such – but nevertheless, you might be surprised to learn that there could be fly larvae lurking in your mushrooms. According to FDA rules in the USA, canned mushrooms are allowed to contain a maximum of 19 maggots, less than five of which can be more than 0.1in (2mm) long. And it's not only mushrooms that might contain these unsettling stowaways; the FDA permits a certain percentage of 'natural contaminants' (translation: bugs, mould, fly eggs and rodent hair and droppings) in many packaged foods.

Shellac is a natural resin that's often used to add a glossy coating to foods like jellybeans – but it can also be found in nail varnishes, wood finishes and furniture polish. A sticky substance excreted by the female lac bug native to the forests of India and Thailand, shellac can even be used to give a glossy shine to citrus fruits and apples. Approved for use in food in most countries, shellac is typically labelled as additive E904.

Vegetarians and vegans might want to check the label on cans of refried beans carefully. Many brands, fast food outlets and restaurants use lard – rendered pork fat – to add an especially savoury and rich flavour to their products. Not all refried beans are made alike, though; while popular brands like Old El Paso list lard in their ingredients, vegetarian and vegan takes on the tinned food staple are also available.

Noticed an ingredient called propylene glycol listed on the back of your cake mix? This synthetic compound is used in everything from antifreeze to electronic cigarettes – and, somewhat unappetisingly, it can also be found in some cake mixes and soft drinks in the United States. The approved quantity of propylene glycol in food differs between the US and most of Europe, where rules are set in place to limit people's intake of the controversial product.

From salmonella to norovirus, salad leaves can easily pick up a range of bacteria from the soil they grow in. So, before they're packed in bags and labelled as pre-washed or ready to eat, they're often cleaned in a harmless low-chlorine solution to kill bugs and remove any bacteria. Even though the idea of washing salad in chlorine hardly seems pleasant, it means the leaves are safe to consume.

Although most chewing gum is made from synthetic materials these days, some varieties contain lanolin, an oily substance found in sheep's wool that protects it from getting wet. Not harmful to humans, it can also be found in a range of beauty products and cosmetics, as well as vitamin D supplements. Lanolin (and a range of other ingredients) are usually referred to as 'gum base' on ingredients lists, so it can be hard to tell whether it's made its way into your chewing gum.

Sodium bisulphite is a chemical additive that's commonly found in crisps – it releases sulphur dioxide gas, which prevents bacterial growth, increases shelf life, and helps to prevent discolouration. However, you might be surprised to find out that it's also commonly used in toilet cleaners and dishwasher products. Also referred to as sodium hydrogen sulphite or E222 on food labels, it's approved for use in food in both the US and the EU.

Chances are you currently have a shop-bought loaf of bread, packet of biscuits or cake in your kitchen. L-Cysteine, called E920 on the label, is an amino acid that's used not only to strengthen the dough, but also to improve the shelf-life of such products. What might surprise you is that this additive comes from duck and chicken feathers, cow horns, pig bristles and even human hair, which is dissolved in acid to isolate the L-Cysteine compound. Although most L-Cysteine is synthetically produced these days, most labels don't disclose where the additive has been sourced from.

Not all viruses are bad; in fact, some are used by food producers to kill bacteria and protect us from illnesses. Bacteriophages are tiny viruses sprayed on ready meals, plastic-wrapped deli meat and other products to destroy listeria, E. Coli and other germs. Approved by the FDA for use in the US in 2006, the six-virus cocktail does not affect humans and is marked as 'bacteriophage preparation' on food labels. Although it's not currently approved by the EU, some European countries allow its use under national rules.

Castoreum, a substance secreted by a beaver's rear end, is used by the rodents to mark their territory – but it can also be used to enhance vanilla, strawberry and raspberry flavourings. In the USA, the FDA closely regulates what goes into vanilla flavourings and extracts, and generally, the use of castoreum has dropped because of how expensive it's become. However, it's hard to spot on ingredients lists; in the US, castoreum is deemed generally safe, so even if companies are using it, you'll only see it labelled as 'natural flavouring'.

Now discover the surprising foods that have been banned around the world