A close inspection of the nutrition label on most processed foods will usually turn up—among other disturbingly-named ingredients whose function is unclear—something known as “hydrolyzed soy protein” or “hydrolyzed wheat protein”.
What is it, and why is it added to so many processed food products?
What Is Protein, Anyway?
“Protein” is a generic term for an animal or plant tissue made out of individual proteins. These individual “proteins” are just long chains of amino acids linked together, end to end.There are 20 amino acids in our genetic code, each an individual molecule with its own shape—and the sequence of amino acids in a protein determines its three-dimensional shape. Our cells can build anything from collagen to digestive enzymes out of the correct sequence of amino acids! A short protein is called a “peptide”, but there’s no set number of amino acids under which the term is used. Calling a protein a “peptide” is like calling a person “short”: it’s a relative judgment.
Why Is There So Much “Hydrolyzed Vegetable Protein”?
Now that we know proteins are just strings of amino acids, we can understand what “hydrolyzed vegetable protein” is. Note that it’s no longer legal to use the term “hydrolyzed vegetable protein” on a nutrition label in the USA: the source of the protein must be listed, e.g. “hydrolyzed soy protein”, “hydrolyzed wheat protein”. (Source: USDA Flavorings FAQ.) The process of extracting seed oils from soybeans or corn (a disturbing series of chemical reactions involving hexane, taking place in chemical plants that look a lot like oil refineries) leaves behind dehulled, defatted soy or corn meal. Typically this mush is fed to cattle…but since it’s cheap and produced by the ton due to massive, destructive subsidies for industrial monocrop agriculture, there is great financial incentive to figure out how to feed it to humans.
Wheat protein is simpler to produce: since gluten (the collective name for wheat proteins, including both glutelins and gliadins) doesn’t dissolve in water, wheat flour is simply washed with water to dissolve away the starch. (How it’s done, featuring lots of delicious phrases like “homogenized slurry”.) As one might expect from the name “gluten”, the result is…gluey. (This is what gives bread it’s stretchiness.) As anyone who’s ever used nutritional yeast by mistake, instead of baking yeast, can attest, the result is a heavy, indigestible solid with the approximate density of a brick and the consistency of hardened wood glue. And wheat flour dissolved in water makes an excellent adhesive for putting up posters…or even wallpaper.
This lack of digestibility is among the many reasons why wheat protein, in addition to all its disruptive effects on intestinal function, is the lowest-quality protein commonly available. (Other reasons include a deficiency of the essential amino acids lysine and methionine.) Whole wheat protein scores only 0.25-0.42 on the PDCAAS, with beef protein at 0.92, and eggs and milk at 1.0. Corn protein isn’t any better: it scores between 0.22 and 0.46. (Even soy scores a 1.0 on the PDCAAS—though soy products cause other issues I don’t have space to discuss here.)
Therefore, fake vegetarian meat substitutes like seitan, veggieburgers, and Tofurky—which usually use gluten to help simulate the texture of meat—are using the most biologically disruptive and lowest-quality protein available.
What Is “Hydrolyzed Vegetable Protein”?
The protein we’ve extracted can be spray-dried into “textured vegetable protein”, which would require another article to explain, or the protein can be “hydrolyzed”. Hydrolysis is basically chemical digestion on an industrial scale: the protein is dropped into a vat of sulfuric acid, boiled for several hours to over a day in order to break down the proteins, after which lye is added to raise the pH back to neutral. (Yum!) I’ve been asked “If our stomachs can digest protein in a few hours, how come it has to be boiled in sulfuric acid for up to a day?”
Answer: our stomach isn’t just an acid vat. Both our stomach and our intestines contain proteolytic enzymes, like pepsin and trypsin—chemicals specifically tuned to break down bonds between amino acids. However, when hydrolyzing protein on an industrial scale, sulfuric acid and heat is generally cheaper than enzymes.
The longer a protein is hydrolyzed, the more that big, long, gluey proteins (like wheat gluten) will be broken down into shorter proteins—or even into individual amino acids.
Why Is Protein Hydrolyzed, and Why Is Hydrolyzed Protein In So Much Of Our Food?
If you’re thinking this all seems like a lot of work for not much benefit, you’re not alone. Hydrolyzed protein usually shows up near the end of the ingredient list: why would food companies go to so much trouble just to add a tiny bit of protein to their food?
The answer is simple: when we hydrolyze a protein down to free amino acids, one of the amino acids we get is glutamic acid, known as glutamate in its anionic form. And since wheat gluten in particular contains a lot of glutamine, hydrolyzed wheat protein will contain a lot of free glutamate