Recently there has been a frenzy of articles about cheese manufacturers producing “fake” cheese. It has been said that grated or shredded cheese, particularly parmesan cheese are being adulterated with wood. This is a gross misrepresentation of the actual facts. What is true is that the cheeses contain a food additive known as cellulose, which is commonly derived from wood.
Cellulose is not wood !
Cellulose is a natural polysaccharide found in the stems and branches of many plants. It is the major component responsible for the structural rigidity of plant cell walls (mammalian cells do not have cell walls). There are many valid and valuable uses for cellulose in food. For decades, it has been used as a food additive to increase fiber content, reduce saturated fat and total fat content, and even to substitute for allergenic food ingredients such as, gluten.
What is of Cellulose?
Cellulose is a linear polymer of glucose residues. This basically means that cellulose is made up of a chain of sugar molecules. Cellulose is structurally identical in composition to starch (amylose), the only difference is the way that the glucose subunits are linked. The difference in linkage results in cellulose having the ability to form fibrils that make them very strong and rigid. For example wood is made of almost 50% cellulose.
While structurally similar, humans are able to digest starch (amylose) but not cellulose. Humans possess amylase, the digestive enzyme present in all mammals, responsible for digesting starch. However, they lack the enzyme cellulase, which is responsible for the break-down of cellulose. Cows and sheep can digest cellulose in grass and other plants, but this is due to a cellulase-producing bacteria found in their gut.
Cellulose in food
Sources. The most common source of cellulose is wood and cotton, it can also be synthesized by bacteria. Though obtained from wood, paper, cotton, and agricultural waste, such as, corn husks, cellulose is not used in its original form. It must be converted into more soluble derivatives knows as cellulose ethers. The most common modified cellulose used in industry is carboxymethyl cellulose (CMC).
Carboxymethyl Cellulose. Unlike raw cellulose, CMC is a water soluble. The white to cream colored, tasteless, odorless, free-flowing powder is used in food, detergents, personal care, and pharmaceuticals amongst other things. As a food additive it is used as a suspending agent, water loss reducer, thickener, emulsifying agent, stabilizer, and dispensing agent. It is commonly used in the form known as cellulose gum. CMC creates an effective barrier against oxygen, carbon dioxide and lipids and therefore, used as a preservative to coat fresh fruits, such as apples. Due to its ability to absorb water, it maintains moisture while improving the texture and overall structure of breads, and thus used as a stabilizer in baking goods.
Cellulose and Cheese
Cheese is a concentrated milk solid, primarily composed of insoluble proteins known as caseins, and fats. CMC is used during the production of cheese to recover protein that is precipitated out of whey. It is also used to mimic the textural and sensory properties of fat in the overall quality of low-fat and non-fat cheeses. In shredded cheeses it is used to prevent moisture loss and caking/clumping.
Safety of Cellulose and Cellulose Derivatives/ethers
While it is true that cellulose is indigestible, its passes unchanged through the gastrointestinal tract. Since it is not metabolized it offers no caloric value, but such is the same for artificial sweeteners made of sucralose.
Cellulose is also used as a binder in dietary supplements. The safety of cellulose and its derivatives being used in food and pharmaceuticals has been studied extensively in humans and animals, and does not pose a hazard to human health. Cellulose as a food additive is non-toxic and non-allergenic.
Although not normally consumed as food, food additives are intentionally added to foods for various functional purposes. The amount of cellulose additive in shredded cheese was recently found to exceed the limits set by the FDA, but we are not eating bits of wood when we sprinkle parmesan on our pizza and pastas. Neither is the use of cellulose in cheese unnatural or uncommon. In fact cellulose is both a renewable and biodegradable resource.