Soy Sauce — An essential Inuit condiment

Living and thriving cultures innovate, adapt and incorporate from other cultures. As the next topic in our series on chemistry and Inuit life & culture,¹ we have chosen soy sauce. Though part of Chinese cuisine from way back in the mists of time, it is a relatively recent addition to the Inuit diet and in a unique context: Arctic Char, both frozen (Kuak in Inuktitut) and dried (called Pitsik) are dipped in soy sauce.

Arctic char

The Arctic char, known as iKaluk in Inuktitut, is closely related to both salmon and lake trout. It is native to Arctic and sub-Arctic waters. With bright red to pink flesh, Arctic char can weigh up to 9 kg, though about 
5 kg is more typical (Figure 1). 
 

Figure 1.  Chaim Andersen with Arctic char (credit: Paul McCarney)

The flesh of Arctic char contains significant concentrations of carotenoids, hence the red colour (Figure 2), which are known antioxidants and provide a variety of health benefits. 

Figure 2. Arctic char, filleted and cut to hang and dry. (credit: C. Andersen)

Even more importantly, Arctic char contain exceptionally high concentrations of omega-3 fatty acids which are vital to good health.² Omega-3 fatty acids specifically contain a double carbon-carbon bond three carbon atoms away from the (end) methyl carbon atom. A space-filling representation of eicosapentaenoic acid, one of the omega-3 fatty acids in Arctic char, is shown in Figure 3.

Figure 3. Space-filling representation of the eicosapentaenoic acid molecule, 
upload.wikimedia.org/wikipedia/commons/4/4a/Linoleic_acid3D.png

Soy sauce

The Inuit have made soy sauce their condiment of choice for Arctic char and other marine food sources. Believed to have been first produced in China about 2,200 years ago, real soy sauce is made from a fermented paste of soybeans, roasted wheat grain, salt water and specific moulds (fungi).³ The fermentation or brewing process takes about three months. Soy sauce produced by the traditional method is usually identified on the label as having been ‘naturally brewed’ or ‘traditionally brewed’ (Figure 4). The contents of such a sauce are typically: water, soy beans, salt, wheat flour.

Figure. 4.  The label of a bottle of traditionally brewed soy sauce

Among many other healthy molecules, soy sauce is rich in niacin. Niacin (Figure 5) is one of the B₃ family of vitamins (insufficient niacin in the diet can cause nausea, skin and mouth lesions, anaemia, headaches and tiredness). As an added health bonus, fermentation of soy beans produces a number of antioxidants. In fact, real soy sauce is far richer in antioxidants than red wine. 

Figure 5. Ball-and-stick representation of niacin
https://en.wikipedia.org/wiki/Niacin#/media/File:Niacin-3D-balls.png

Fake soy sauce is everywhere!

Before soy sauce users congratulate themselves on eating healthily, they should realize it is unlikely that they have been consuming brewed soy sauce but instead have been consuming chemically-hydrolysed soy sauce. Soy-sauce-producing companies do not want to wait three months for each batch: instead, the soy beans are acid-processed as Joe Schwarcz has described:

"The cheaper "chemical" version can be produced in a day simply by adding hydrochloric acid to a defatted mash of soybeans, followed by neutralizing with sodium carbonate. But this is a brutal method that breaks proteins down to individual amino acids and the resulting flavour and aroma are quite different from fermented soy sauce. Undesirable compounds such as dimethyl sulphide and formic acid are also produced. Absent, though, is the brown color produced by fermentation products, and this is solved by the addition of caramel colouring.⁴"

In addition, chemically-hydrolysed soy sauce is high in added sugars. A typical label will note the contents as: water, glucose-fructose, salt, caramel, hydrolysed soy protein, corn syrup, citric acid and sodium benzoate.  There are no health-beneficial compounds produced during chemical hydrolysis. Unfortunately, the only common brand of soy sauce in stores in Inuit communities is that of the chemically-hydrolysed soy sauce.

An additional concern in consuming chemically-hydrolysed soy sauce is that the glycerol by-product of soy chemical hydrolysis reacts with hydrochloric acid to produce 3-chloro-1,2-propanediol (3-MCPD)⁵ and 1,3-dichloropropane-2-ol. Some imported brands of chemically-hydrolysed soy sauce contain excessive levels of these probable carcinogens and teratogens (Health Canada has established 1 ppm as the maximum ‘safe’ level of 3-MCPD in chemically-hydrolysed soy sauce).
 

CH₂(OH)CH(OH)CH₂(OH)(aq) + HCl(aq) → CH₂(OH)CH(OH)CH₂Cl(aq) + H₂O(l)

CH₂(OH)CH(OH)CH₂Cl(aq) + HCl(l) → CH₂ClCH(OH)CH₂Cl(aq) + H₂O(l)

Food for thought!  

Our message is one of caution for all soy sauce consumers (always read the label — and know some consumer chemistry!). For Inuit, whose diet for thousands of years has enabled them to live healthy lives (a topic for a future article), it is regrettable that one of the condiments incorporated into their diet should commonly be one which is actually unhealthy. For Inuit, we contend, consumer activism is necessary to ensure that healthy foodstuffs are imported to the northern communities. Sadly, ‘imitation’ soy sauce is the least of Inuit health worries relating to chemical compounds, as we will describe in our next article.

Questions

1. Investigate the bottles of soy sauce in stores where you live.  From the ingredients listed on the label, does the bottle contain fermented or chemically-hydrolysed soy?
2. Check grocery shelves and see if you can find another product that has a misleading label.
3. According to Health Canada 1.00 ppm (1.00 mg per 1.00 kg) is the maximum permissible level of 3-chloro-1,2-propanediol in soy sauce. In a 150 mL bottle of soy sauce (density 1.20 g⋅mL⁻¹) what will be the maximum allowable mass of 3-MCPD? How many moles does this represent? How many molecules will this be?
4. Draw the structural formula of 3-chloro-1,2-propanediol.
5. Give a chemical definition of the term ‘hydrolysis reaction.’

Answers 

1. Usually both fermented and chemically-hydrolysed soy sauce is found in urban-area stores, but rural — especially northern stores — often carry chemically-hydrolysed soy sauce only.
2. Many possible answers! For example, ‘processed cheese’ does not always contain ‘real cheese’; ‘coconut milk’ often contains thickeners, such as guar gum; ‘sour cream’ does not necessarily contain cream; and ‘peanut butter’ usually contains many more things than peanuts.
3. Mass of 3-MCPD = 1.80×10⁻⁴ g; moles = 1.63×10⁻⁶ ; molecules = 9.82×10¹⁷ 
4. 
    

5. A hydrolysis reaction occurs when a covalent bond is broken in a compound by insertion of a water molecule. One bond site is occupied by the hydrogen atom and the other bond site by the hydroxyl group.

References (online access September 2018)

1. C. Andersen and G.W. Rayner-Canham, “Ramah Bay – 7,000 years of Aboriginal Culture – and Chemistry,” Chem 13 News, September 2018.  
2. Wikipedia: “Fish Oil.” 
3. Wikipedia: “Soy Sauce.” 
4. J. Schwarcz, “Saucey Sham,” Canadian Chemical News, 2010, 62(7), 30.
5. Wikipedia: “3-MCPD.” 

About the authors

Ms. Chaim Christiana Andersen is an Inuit from Nain, Nunatsiavut, currently an undergraduate student in the Environmental Science (Chemistry) program at the Grenfell Campus of Memorial University, Corner Brook, Newfoundland. Dr. Geoff Rayner-Canham is Professor of Chemistry at the Grenfell Campus.