There’s nothing quite like a fresh portion of fish and chips after a long day at the beach.
While many chippies might think they’ve perfected their recipes, scientists believe there is still room for improvement.
To celebrate National Fish and Chips day, MailOnline asked the experts for the secret to the perfect fish supper.
From cracking open a cold can of Guinness to pressurising your mix with Nitrous Oxide, these strange tips could be the secret to banishing soggy batter.
And, for the richest experience possible, scientists say it is best to eat your fish and chips while sitting at the seaside and listening to the waves.
Scientists have revealed that the perfect fried fish recipe involves adding Guinness and pressurising that batter using nitrous oxide
The science of getting battered
Before you start warming up the fryer, it’s important to understand some batter basics.
Batter acts like a thermal blanket around delicate foods like fish, preventing too much heat reaching in while also preventing steam from leaking out.
When this goes right, the batter steams the fish inside a protective layer while also repelling the oil to leave a crunchy exterior.
This is possible because batter is made largely out of two important ingredients: water and starch.
The moment this mixture hits the hot oil, several chemical processes start to happen at the molecular level which allows a light crust to form.
As the hydrated starch in the batter heats up it starts to undergo a process called ‘starch gelatinisation’, becoming a glue-like gel which envelopes the fish.
At the same time, water trapped in the batter instantly explodes into steam, forcing itself out of the mixture in a bubbling torrent.
Dr Sue Bailey, a food scientist from London Metropolitan University, told MailOnline: ‘When battered fish is fried it becomes crispy because oil gets to a higher temperature than water.
‘The moisture in the fish and batter quickly turn to steam and this escaping stem prevents the oil from penetrating the food and turning it greasy.’
Driving the water out of the batter also causes the gelatinised layer of starch to dry out and harden, setting it into a hard crunchy layer.
Finally, Dr Bailey explains that the surface browns as the proteins and sugars in the batter react through a process called the Maillard reaction.
If everything has gone to plan, this should leave you with a batter that is golden brown, crunchy, and not greasy.
The crispy batter around your fish is the product of several complex chemical interactions, using science we can improve these reactions to get an even better piece of fish (stock image)
The dry ingredients
Typically, chip shop batter is made of a mixture of plain flour because this contains the right mix of starch for crispness and gluten which gives the batter structure.
But with an understanding of batter science, we can do a lot more to enhance the crunch and flavour of our fried fish.
Barry Tonkinson, director of culinary research and development at the Institute of Culinary Education, recommends using a chemical called wheat dextrin.
Dextrins are a type of soluble fibre made when long starch molecules have been broken down into smaller pieces by water.
Wheat dextrin is formed as a byproduct of cooking in places like the crispy brown part on top of fresh baked bread but it can also be used as a food additive.
Unlike normal flour, wheat dextrin is essentially 100 per cent starch and contains almost no gluten whatsoever.
This promotes more starch gelatinisation which means the batter becomes crispier when fried.
Since starch does not easily absorb water, swapping some of the glutenous flour for wheat dextrin also makes the resulting batter stay crisper for longer.
Researcher Barry Tonkinson found that by adding wheat dextrin (shown in sample number four) he could create a batter that was even lighter and crispier than normal
Researchers have also found that adding maltodextrin to batter results in a crust that is deep brown and crisp. These pictures show courgette slices fried with normal batter (left), batter with maltodextrin (middle) and batter made with ethanol (right)
In a blog post, Mr Tonkinson explains that by mixing a commercially available wheat dextrin, Evercrisp, with flour in a four-to-one ratio, you can achieve an unbeatably crisp crust.
Studies have also found that adding the sugar substitute maltodextrin can produce a batter that is lighter, and deeper brown.
Researchers found that the maltodextrin leads to more of the Maillard reaction occurring, leading to ‘improved golden–brown coloring of the crust without affecting oil uptake.’
Cooking with beer
However, just making our batter crisp isn’t enough for the perfect fried fish.
Without air pockets, the batter will just be a thin crisp shell which wouldn’t give a satisfying bite or properly insulate the delicate fish within.
To get the batter nice and light we actually need a way of putting air into the batter so that it can puff up once it hits the hot oil.
Thankfully, the perfect solution is already at hand: beer.
Ethanol from beer in batter evaporates rapidly when exposed to hot oil, creating more air pockets and a crunchier experience. In these microscope photos of fried batter you can see that picture D has larger holes because it was made with ethanol
Dr Bailey says: ‘Cold beer adds three ingredients—carbon dioxide, foaming agents and alcohol—each of which brings to bear different aspects of physics and chemistry to make the batter even more light and crisp.’
The beer’s alcohol content is really important since ethanol has a lower evaporation point than water.
This means that the liquid content of a batter with alcohol will evaporate faster than one which just contains water.
‘The faster the batter dries, the lower the risk of overcooking the food and the crispier will be the batter,’ Dr Bailey explains.
As ethanol evaporates it also creates bubbles which are trapped in the web of gluten stands which then sets into an airy lattice.
One 2018 research paper found: ‘Substitution of water with ethanol in tempura fried squids promotes a more porous, dehydrated and glassy crust structure, which in turn makes the coating crispier and crunchier.’
Beer is actually even better than just using ethanol since the same foaming agents which give your pint its head help to trap bubbles of CO2 and make the batter even lighter.
Guinness is the perfect beer to use in your batter because it contains Nitrous Oxide and foaming agents which create bubbles that are very slow to dissolve
Of all the possible beers you could choose for this application, Guinness stands out as the winning choice.
As Mr Tonkinson points out, Guinness not only adds a delightfully nutty flavour to the batter but also happens to be chemically perfect for this application.
What makes Guinness so good is that each can contains a ‘widget’ full of nitrogen which surges up through the beer when opened.
Nitrogen dissolves significantly slower in water than carbon dioxide, which means that Guinness can make batter stay lighter for longer.
Preparation and frying
With your wet and dry ingredients prepared, it’s now time to mix your batter and get frying.
Research has found that a batter made up of 60 per cent wet and 40 per cent dry ingredients is best.
This ratio allows almost all of the water to be driven out of the batter during frying, leaving it as crisp as possible.
Chef Heston Blumenthal (pictured) recommends using a whipped cream syphon to pressurise batter with Nitrous Oxide
Just as you can use Nitrous Oxide to add air to whipped cream, researchers recommend using the gas to add more air to your batter for a lighter product (stock photo)
One study found that batters at 60 per cent hydration were left with only five per cent of their original moisture content after five minutes of frying.
Once mixed, it is now critical to try and keep the batter as airy as possible for as long as you can.
In his fish and chips recipe, culinary experimenter Heston Blumenthal recommends opening the beer at the very last moment and immediately putting the batter into a whipped cream syphon.
You can then charge this syphon with nitrous oxide, or carbon dioxide if you can’t get your hands on it, to add even more air.
It is also important to keep the syphon as cold as you can while you get everything else ready.
Gluten, which will make your batter tough, is formed by the chemical reaction between water and flour so keeping it cool will inhibit this reaction.
When you’re ready, squirt just enough batter to cover one piece of fish into a bowl, coat it, and then lower the battered fish into 160°C (320°F) neutral oil.
Experts recommend frying at 160°C (320°F) in neutral oil which is hot enough to vaporise the water in the batter but not so hot that the batter burns
You will need to work quickly since the bubbles will begin to dissolve as soon as the batter leaves the syphon, leaving you with a soggy, oily coating.
When the fish is a rich golden brown, pull it from the oil and let it drain on some paper towels to wick away any oil that might soak back into the batter.
Since alcohol-rich batters have so many microscopic holes on the surface, they absorb any nearby oil as they cool so it’s important to get the fish dry.
The perfect chip
Of course, you can’t have the perfect fish without sparing a thought for the humble chip.
Luckily, many of the same chemical principles that make batter crisp can also be used to make crunchy potatoes.
The only difference is that the starch that will form the crisp outer layer comes from the potato itself rather than any additional source like flour.
As potatoes cook, long chains of carbohydrates uncoil into shorter starches which makes the flesh soft and flexible.
Just like batter, these starches then undergo starch gelatinisation and dry out into a crunchy outer layer once the chip is cooked in hot oil.
Experts say that the key to crunchier chips is making that layer of gelatinised starch as thick as possible by starting with a starchier spud.
Dr John Lioumbas, a scientist from the Aristotle University of Thessaloniki, previously told MailOnline: ‘Generally, potatoes with higher starch levels tend to undergo more extensive gelatinization during cooking.’
In his own research, Dr Lioumbas used the Angria variety, but other research suggests that a Russet variety might be best thanks to its high starch levels and good size.
The difficulty is that drying out the starch into a hard layer requires using temperatures that would burn the exterior before the chip can cook all the way through.
The scientific formula for the perfect chip involves three stages of cooking: once in water, once in cooler oil, and once in hot oil
Heston Blumenthal’s recipe for perfect chips (pictured) uses the triple-cook method to boost the thickness of the outer crust while ensuring the centre remains fluffy
This is why Heston Blumenthal developed the ‘triple-cooked chip’ method which has become the standard for top restaurants.
Once cut to size, the chips are boiled for anywhere from five to ten minutes until they are completely cooked through.
To avoid them falling apart completely, add a tablespoon of white vinegar since the acidity slows the breakdown of pectin and ensures they retain their structure.
When the potatoes are cooked through, remove them from the water and allow them to dry out in the freezer for at least an hour.
The arid conditions in the freezer help remove any water which would interfere with the crisping process and the resulting ice crystals burst starchy interior cells to create a fluffier texture.
Next, the chips must be fried at a relatively cool temperature of 160°C (325°F) for about five minutes or until lightly coloured.
The best potatoes for chips are Russets (pictured) or other high-starch varieties. Just like in batter, the more starch there is the crispier the finished product will be
Once the chips have been through their third and final stage of cooking they should be light brown and shatteringly crisp (stock image)
Dr Lioumbas explains: ‘When lower temperatures of oil are utilized, the heat transfer occurs at a slower rate.
‘The slower heat transfer allows for gradual water evaporation from the potato, leading to a softer exterior with less pronounced browning and crispiness.’
Finally, remove the chips and crank up the heat to 180°C (360°F) for the final of the three cooking stages.
This last dip in the oil will drive out any remaining moisture in the outer starch layer and brown the exterior through the Maillard reaction.
This process will leave you with chips that are fluffy and tender on the inside but golden brown and crisp on the outside.
Presentation is key
From the feeling of the cutlery to the sounds you can hear – all the sensory components of a meal will have an effect on your sense of taste.
Even relatively subtle factors like the setting and your mood can result in surprisingly big changes to how we experience a meal.
Food psychologist Professor Charles Spence of Oxford, himself the son of a fish fryer, told MailOnline: ‘The sounds of the sea, not to mention the seagulls, as well as the smell of the salty sea air are all part of the multisensory experience, and can help to enhance the taste of fish and chips.’
Food psychologist Professor Charles Spence says that eating off of paper sheets can actually make the fish taste crunchier and put you in a better mood
Professor Spence helped Heston Blumenthal develop a dish called ‘The Sound of the Sea’ (pictured) which involves playing guests seaside sounds while they eat. By eating near the sea or hearing waves while you eat you can make your seafood taste better
This was the principle behind a dish called ‘The Sound of the Sea’ which Professor Spence helped Heston Blumenthal develop in 2006.
After finding that people found oysters significantly more salty while being played a recording of seaside sounds, Blumenthal designed a hidden speaker inside a conch shell which would accompany the meal.
‘The salty smell of the sea air that you get at the coast is likely an important part of the experience too, though it turns out that it is much harder to bottle that than you might think,’ Professor Spence adds.
Research has also shown that holding something warm in your hand can actually put people in a better mood and even promote feelings of interpersonal warmth.
Professor Spence adds that the ‘rattle of wrapping paper likely enhances perceived crispness of fried fish.’
This means that sitting by the seaside and eating it straight off of paper wrapping is actually the scientifically best way to enjoy your fish and chips.
Finally, while researchers are yet to weigh in on the matter of mushy peas, there are some scientific tips for how to apply vinegar.
The acid in vinegar helps to cut through any of the oil which might have soaked into the fish.
But drowning your perfectly crispy fish with vinegar until it was soggy would undo all the crispness that was carefully cultivated.
Therefore, Dr Spence recommends spraying vinegar over the fish rather than pouring it.
By aerosolising the vinegar we can smell it more easily and thereby elevate the experience while only using a light, even coating.
