Food & Drink, News

Filling forensics – the science behind the perfect sandwich and how to stop the sog

We’ve been building our sandwiches all wrong according to a new study by the  University of Leeds 

In preparation for British Sandwich Week (16th to 22nd May) experts at the University of Leeds have been studying the science behind what stops sandwiches from going soggy, and the optimum way to build them for a satisfying mouthful of all the fillings in one bite.

Many of us have been making our lunches at home for nearly 420 days and while some have perfected their sandwich-making skills, there have also been some epic sandwich fails. But it seems we have been making our sandwiches subpar for years, and now the science behind the perfect sandwich is out.

And the trick is in the construction.

Professor Alan Mackie, Head of the Food and Nutrition School at the University of Leeds, says: “There are three main areas of consideration – the bread, the spread and the filling. The trick is to place both pieces of bread side by side, then spread, place primary fillers on each slice, and finally add salad in the middle and place them together – rather than building your sandwich from the bottom up.”

So, for example, place cheese on one half, ham, or other protein on the other, and the salad and wet ingredients need to go in the middle. The scientists say doing it this way reduces ‘the sog’.


Symmetrical sandwiches ‘stop the sog’

Dr Sally Moore, Lecturer and Registered Dietitian also of University of Leeds added: “The way to stop ‘the sog’, is to keep the moist ingredients away from the bread. People tend to construct their sandwiches vertically by buttering one layer of bread, then adding the layers of fillings, whether that is cheese, meat, or another protein, then putting salad on top, and finishing with another slice of bread as a lid.

“In most cases, the salad or greens are the wettest ingredients, but adding lots is going to help you achieve your 5-a-day fruit and vegetables where a lot of the moisture will be. So, we’d definitely recommend constructing sandwiches in a more symmetrical way. Butter two slices of bread, add half of the filling to each slice and then put the salad in the middle.

“Create a moisture shield with butter, mayo, mustard, hummus or whatever spreadable condiment you fancy to create a barrier between the wet ingredients and fillings, and the bread. Remember to spread right to the edges to create the seal to combat the moisture.

“Also, use your loaf to choose your loaf – the sog is more likely with sliced white bread so go for sourdough, wholegrain or brown, all of which will bring a firm texture, a sturdy sandwich, as well as health benefits.”

In agreeance that the bread chosen is key, is Registered Nutritionist and spokesperson for Bertinet Bakery Sourdough, Jenna Hope, who said: “The fibre and fermentation process in sourdough is central to its gut health benefits and as a nation we are not getting enough fibre. In the UK just 13% of men and 4% of women are reaching the recommendations for fibre of 30g per day. So, I would suggest using this specialist week to try sourdough, up your fibre and construct some great sandwiches.”

So, this British Sandwich Week, celebrate the great British butty and follow the science to get the basics right so you can take pride in your creation.

Make your sandwich instantly instagrammable and boost your five a day intake with colourful ingredients – spinach, radish, peppers, shredded red cabbage and carrots add a pop of colour and bring texture and taste for butty bliss.

Jim Winship, Director of The British Sandwich & Food To Go Association behind British Sandwich Week says: “As lockdown restrictions ease and we move into the summer, we know people will be making sandwiches, for picnics, or for on-the-go to a much-needed meet up. And it’s important to get it right, so the occasion isn’t ruined by a soggy mess.”

““For many, however, the return to getting out and about means they can abandon the limited choice of ingredients at home for the convenience and wider range of options that the professional sandwich industry has to offer – and, in the knowledge, that in doing so they are helping this huge industry to get back on its feet. Sandwich shops, supermarkets, and retailers will have their fridges stacked high with freshly made sandwiches for British Sandwich Week, so look out for your favourite fillings or try something new – you might even find a Christmas dinner sandwich out soon!”

Sally Moore’s advice: “Don’t forget to check the nutrition information on food labels to help you assess how healthy these products are or ask for this information before you order.”

Up your sandwich game – here are eight tips to create the perfect sandwich that will stay crisp and fresh until you are ready to enjoy it, whether that be at your place of work, at a picnic, or on-the-go.

  • Layering is key – plan your layers so they are in the right order
  • Make sure your butter is spreadable and not too much or at room temperature – and spread right to the edges evenly
  • Fold your meat rather than lie it flat
  • Dry your greens – if using salad leaves, pat them dry with kitchen paper
  • If you’re taking your sandwich to work or on a picnic, store the sliced, wet ingredients separately (e.g., tomatoes, cucumber, pickles) and add them in when you’re ready to eat it
  • Mix it up – don’t eat the same sandwich every day – mix it up so your lunch is a treat and adds excitement to your day
  • Use up leftovers as fillings to avoid food waste
  • Eat mindfully – switch off the TV, put your phone away, sit in a comfortable chair, and savour every bite!


  • Using two crusts from the loaf
  • Using butter straight from the fridge so it rips your bread
  • Cutting the pieces unevenly – what monster slices their sandwich unequally?
  • Don’t drown your bread in mayo / mustard
  • Using the wrong knife to slice – make sure you have a sharp, serrated bread knife to cut through all the layers cleanly, so you don’t end up with a massacred mess
  • Take the paper off your cheese slice!

Every year British Sandwich Week celebrates the humble sandwich in all its glory as well as the contribution that the sandwich industry makes to the economy. This year, it has the even greater aim of supporting the industry as it comes back after a year of lockdowns. Sandwiches are a British staple to be enjoyed at any time of the day, and it’s very clear that as a nation we still love our sandwiches.

British consumers manage to munch their way through over 11.5 billion sandwiches each year. If you laid each one end to end, they would go around the world about 44 times. More than half of these were made and eaten in the home.

What is a sandwich? The British Sandwich Association defines a sandwich as: Any form of bread with a filling, generally assembled cold – to include traditional wedge sandwiches, as well as filled rolls, baguettes, pitta, bloomers, wraps, bagels, and the like, but not burgers and other products assembled and consumed hot. Hot eating sandwiches are also included.


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