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“Now you know why he carries his baguette in this fashion!”

Chuckles usually erupt when I make this comment in a talk on food additives as I simultaneously show a picture of a man sporting a beret and holding a bottle of wine, making him instantly identifiable as French. The kicker is that he has a baguette tucked under his arm. My little joke caps a discussion of the use of calcium propionate as a preservative in bread.

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Of course, there is a backstory here. One that goes way, way back.

Archeologists have found what look like grinding stones dating back some 30,000 years, possibly for grinding wild grains into food. That’s conjecture, but finding 14,000-year-old charred crumbs of flatbread in the area that is present-day Jordan is believed to be proof of early attempts at bread making. The likelihood is that wild grains were ground and mixed with water to make a paste that was then poured onto hot stones.

Sometime later, it was noted that if this paste were put aside for a few days, it would rise. Dough was born! Baking this in primitive ovens gave rise to bread. Of course, at the time there was no knowledge that it was carbon dioxide-generated by naturally occurring yeasts that makes the dough rise, and that yeast also produces a host of compounds giving bread a delectable flavour. This stimulated the cultivation of wheat beginning some 10,000 years ago. We have been enjoying bread ever since.

However, the road to that enjoyment has been marked by potholes. Most recently, there has been concern about gluten, a network of proteins found in wheat that traps carbon dioxide and is responsible for the texture of bread. Some unfortunate people, generally estimated to be less than one per cent of the population, are afflicted with celiac disease, a chronic, serious condition that is triggered by the ingestion of gluten and affects the digestive and immune systems. There is no question that celiacs have to scrupulously eliminate all traces of gluten from their diet.

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But many “wellness influencers,” with no background in science, also urge all their followers to avoid gluten, claiming that it generally impairs health. While there is evidence of some consumers of gluten experiencing short-term bellyache and bloating, a condition termed “non-celiac gluten sensitivity,” it is rare, afflicting less than six per cent of the population. Nevertheless, this has given rise to a marketing bonanza of gluten-free products, demonstrating the ease with which pseudoscience slithers into our lives.

A pothole that was encountered long before the gluten issue was spoilage. Naturally occurring fat in grains can react with oxygen in the air and break down to produce compounds that can give bread a “rancid” taste and smell. There is no health danger here, but moulds are a different story. These microbes, present in soil and air, can get a foothold in the moist, nutrient-rich environment of bread and multiply. This is more than a cosmetic concern because moulds can produce toxic metabolites.

And then there is a problem that has plagued bakers since ancient times, a condition known as “ropiness.” This is well named because it is characterized by the inside of a loaf being converted into a mass that resembles a tangle of strings that make for an unpleasant chewiness. To make matters worse, rope formation is accompanied by the release of volatile compounds such as diacetyl, acetoin, acetaldehyde and isovaleraldehyde that produce a scent resembling that of rotting melons or pineapples.

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Ropiness is caused by the action of several bacterial species of the genus bacillus. These do not cause disease, but they release enzymes that decompose wheat starch and proteins into smelly compounds. At the same time, they secrete their own proteins and polysaccharides that cause discoloration and slimy rope formation. These bacteria and their dormant forms called spores are ubiquitous and are found in plants, soils and even baker’s yeast. While heat destroys the bacteria, their spores survive baking. The moist and low-acid conditions present in bread make for an ideal environment for the spores to burst into life and cause mischief.

By the early 20th century, the science of bacteriology, spurred by Louis Pasteur’s pioneering studies of microbes, had been established. Since it was clear that bacteria play a role in disease and food spoilage, the search for antibacterial substances was on.

Acids were found to be the enemies of bacteria, so these served as a natural starting point. An interesting clue was discovered in Emmental cheese, produced since the 13th century in Switzerland. The holes in the cheese are the result of carbon dioxide being formed by bacteria that are naturally present in raw milk. These also form propionic acid that imparts a characteristic flavour to the cheese, and given the long history of the cheese, do not pose a health concern. Various experiments with propionic acid and its salts were undertaken with the conclusion that calcium propionate added to bread dough prevents contamination by moulds and interferes with the growth of bacteria that produce ropiness.

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Calcium propionate is now commonly added to bakery flour to an extent of 0.3 per cent, which is less than the one per cent found naturally in Emmental cheese. Sourdough is an exception because its content of lactic acid produced by the added bacterial culture serves the same purpose as propionates. The safety of calcium propionate was underlined by the discovery that propionates are a normal product of fat metabolism and that we naturally produce these compounds in our body. Today, calcium propionate is produced by neutralizing propionic acid with calcium hydroxide, with the propionic acid in turn being made by reacting ethylene with carbon monoxide and water using a cobalt or rhodium catalyst.

Now back to my Frenchman. The French are famous for the attention they give to food, particularly their pastries and baguettes. Indeed, a law passed in 1993 regulates that any bread sold as “traditional” cannot contain additives. Only flour, water, salt, baker’s yeast and lactic acid-producing cultures are allowed.

The absence of calcium propionate is not a problem because traditional baguettes are consumed the same day they are baked, so there is no time for bacillus spores to awaken and cause ropiness. And the ropiness is further prevented by carrying the baguette under the arm. Since we naturally produce propionates in our gut, from where they enter our bloodstream, and thence our sweat, the traditional French method of transport makes for an effective natural preservative.

Joe Schwarcz is director of McGill University’s Office for Science & Society (mcgill.ca/oss). He hosts The Dr. Joe Show on CJAD Radio 800 AM Sundays from 3 to 4 p.m.

[email protected]

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