How safe is your crust?
What is acrylamide, and do we need to worry?
I consider eating a slice of freshly baked sourdough one of life’s greatest pleasures – that open tender crumb and golden dark crust are irresistible. But over the past year or so, some of our students have voiced concerns about a potentially-carcinogenic chemical found in the dark crust of baked bread, known as acrylamide.
Acrylamide is a chemical that forms naturally in starchy food products, including potatoes, cakes, cereals and coffee, when you bake, roast, fry, grill or toast them at high temperatures (above 120ºC). It forms as part of a chemical reaction between sugars and amino acids, and occurs when we bake bread – any bread, including sourdough. Naturally, because of its link to cancer, it can worry people, particularly if they are following a cancer prevention or management diet.
The very act of baking creates what is known as the Maillard reaction. This is the name of the process that produces the classic, burnished, dark, rich, sweet and delicious crust. It gives a sourdough loaf its beautiful colour, flavour and texture. However, the Maillard reaction also produces acrylamide and laboratory studies have shown acrylamide to be a potential carcinogen. I use the word ‘potential’ because the tests on rats and mice showed that acrylamide reacts with DNA (the genetic material in cells) and damages it. It is this damage that could be a cause of cancer.
When we eat foods containing acrylamide, the compound is absorbed by the gastrointestinal tract and distributed through the body, along with all the other metabolites. One of the main metabolites derived from acrylamide is glycidamide, and it is this that is most likely the root of the gene mutations associated with the tumours seen in lab rats. Given the results of this study, conclusions have been drawn by the food industry, not unreasonably I might add, that acrylamide might also be carcinogenic in humans.
I think that it is important to look at the whole bread-making process and one of the key considerations is that there are also other reactions that occur with other compounds which may act as a counterbalance to acrylamide in bread. As the crust bakes and the Maillard reaction occurs, there is a simultaneous reaction of another amino acid, which creates an antioxidant called pronyl-lysine which is simultaneously created when the starch and sugars react with amino acids, in this case, an amino acid called l-lysine. It’s like nature created a balance.
Pronyl-lysine is believed to increase cancer-preventing enzymes with researchers suggesting that pronyl-lysine can lower the risk of colon cancer. Again, however, this was concluded from another study carried out on rats.
It’s worth noting that wholegrain bread has a higher concentration of pronyl-lysine in its crust than white bread, which is another argument for eating whole grain breads. And we know from studies that pronyl-lysine is up to eight times more plentiful in the crust in comparison to the interior of a loaf.
Another study on Lunasin– a polypeptide that has been demonstrated to exhibit marked anti-cancer activity – examined the synthesis of this cancer preventative peptide (protein) by lactic acid bacteria during the process of sourdough fermentation. It was a small study, in vitro, however, the findings were that the fermentation of grains by lactic acid bacteria increased the concentration of Lunasin (by 2–4 times) to levels that the authors concluded might suggest new possibilities for exploring biological synthesis and formulation of functional foods. It is not something we can draw concrete conclusions from to make any statements about potential health benefits but nevertheless it’s another study that shows other processes are happening during the sourdough process, and in my view demonstrates that we should not consider the findings of a single aspect of fermentation in isolation.
HOW TO REDUCE THE RISK OF ACRYLAMIDE IN SOURDOUGH
You don’t have to bake your sourdough dark. Eating bread that’s baked to the point at which the crust has a light golden colour is probably the best advice to anyone who has an increased risk of cancer.
DON’T BURN YOUR BREAD
If you want to bake your sourdough dark there can be a fine line between a beautiful burnished, caramelised crust and being burnt. It is about maximising all the flavour and texture of the loaf and producing bread that is delicious, without burning the crust.
TOAST LIGHT OR NOT AT ALL
The toasting process is also a process that can increase the acrylamide content of the food. Eat fresh bread, or if you toast your bread, then toast light rather than dark.
Counterbalance the potentially damaging effects of toasting your bread by eating foods that may help reduce DNA damage such as blueberries and dark fruits, containing high levels of polyphenols. Oxidisation is thought to be a key contributing factor in the development of cancer, and polyphenols are known for their antioxidant properties, providing a range of health benefits from preventing cancer to reducing the risk of cardiovascular disease. Potent antioxidants such as these help to fight inflammation and reduce DNA damage and LDL oxidation in the body.
Whole grains contain about 20–30 different types of polyphenols, flavonoids with phenolic acids being the most abundant, and they are mainly located in the outer layers (e.g. the bran) of cereal grains – not just wheat, but other grains such as barley, oats and rye.
By including wholegrain in your bread your body may well be better equipped to counteract the oxidative damage and inflammation associated with acrylamide.
FERMENT LONG AND SLOW
Studies also suggest that the long slow fermentation of the sourdough process results in higher bioavailability of the phenolic compounds and antioxidants in the bread.
Try to ensure the bread itself contain high levels of antioxidants by including darker wheat varieties and wholegrain. But more than this, I think it’s about what you eat your sourdough with. I would suggest eating foods with high levels of flavonoids, for example, dark leafy green vegetables, dark berries, including blackcurrants, blueberries and black grapes. We often serve blackcurrant jam, red onion chutney, or red cabbage sauerkraut with our bread, as well as a glass of red wine – all simple and delicious ways to include eating more antioxidants with your bread.
When we see dramatic headlines in the newspapers, it’s easy to start worrying and react negatively towards foods that we may think of as a health risk, but it is important to keep things in perspective and not just focus on one aspect of the story. There is no doubt that you need to look at the bigger picture of bread and sourdough, taking into account the process, the ingredients used, and the way in which you eat bread in order to get a balanced view. I don’t believe that it is healthy to approach any food with a focus on a single aspect.
Personally I love the dark caramelised crust, and while I do appreciate that not everyone does and that people have concerns about it, I also think that we need to keep some perspective. There are extremely tiny amounts of acrylamide in sourdough and it’s worth remembering that man has been eating foods that have been well baked for millennia, in fact for as long as we’ve been cooking, from the time we discovered fire. That said, however, there also are times whem people do need to be mindful of eating potentially carcinogenic foods.
Ultimately, it is about eating delicious bread that nourishes you and that you love. Eating is not just about taste but about your state of mind, and being anxious about your food is no way to enjoy your bread. So bake your bread to suit you, or simply cut the crusts off.
You can find more information about Acrylamide here.