What Does it Mean to be “Food Grade?” In 2014, the food blogger known as Food Babe famously created commotion on the internet with her petition to have “the yoga mat compound” azodicarbonamide removed from Subway bread. Azodicarbonamide is an approved food additive, used as a whitening agent for flour and a dough conditioner in baking; it is also used as a foaming agent in plastic products including yoga mats, hence its catchier alias the “yoga mat compound.” Whether or not azodicarbonamide should be approved for food use is a separate issue, but removing it on the basis that it is also found in yoga mats begs the question: why is no one petitioning for the removal of the “gasoline compound” from our bread?
The “gasoline” compound is, of course, ethanol, and it has a variety of practical applications in food, including its use as an antimicrobial agent in bread products. What makes some ethanol fuel and other ethanol “food grade?” What makes any chemical food grade? At least one woman reportedly ingested 35% food grade hydrogen peroxide, so the answer is clearly not intuitive to everyone. Even to most chemists, the phrase "food grade hydrogen peroxide" may sound alarmingly like an oxymoron.
Food grade ethanol is a fun example, because ethanol is not only a toxin, but is also regularly ingested on purpose. This makes it extra confusing in a world where people tend to equate “chemical” with “toxin” without having a clear definition for either.
For simplicity’s sake, let us say that food grade classification has two components: (1) materials that can come into contact with food during processing or storage, and (2) chemicals that can be added directly to food without rendering it unsafe for consumption. For example, food grade processing equipment or packaging materials will not leach contaminants into food. Food grade chemicals often are involved in processing without being present in the final product, either because they were removed or transformed via chemical reaction. In many cases, the food grade chemical remains, untransformed, in the final product, within a specified dosage limit.
Chemists and food scientists understand that the term “food grade” is contextual, and that the context is a bit more nuanced than not eating the packaging (or the yoga mat). For example, what was the temperature and pH of the food substance when it went through the processing equipment? What classifies as contamination, and what dosage defines the poison? As with most considerations in the food industry, the criticality of this issue can be distilled into two principals. The first is food safety, and relatedly, consumer trust in food manufacturers and regulators. The second is food quality, which relates to the importance of food both as a source of nourishment and as a cultural cornerstone.
Ethanol fulfils a variety of roles in food applications. It may be used as a carrier for flavor extracts or coloring additives, as an antimicrobial agent, and as a flavor enhancer, just to name a few. Ethanol emitters are an example of active packaging used to inhibit mold-growth in bread. From a research standpoint, it is useful as a solvent for chromatography and other separation or extraction methods. As mentioned previously, it is not only the safety of the food in question, but the quality, since impure ethanol can contain volatile organic compounds (VOCs) that impart negative odors even at trace levels.
Just how do we elevate the “gasoline compound” to food grade status? Processing and quality control. Chemically speaking, sucrose is the optimal substrate for ethanol production. Sucrose from sugar beet or sugar cane is readily broken down by yeast cells through fermentation to produce ethanol. However, if you have ever driven through the Midwest, you will not wonder that – as with many things in this country – we have figured out a way to make it from corn. Corn is disadvantageous compared to simple sugars due not only to agriculture factors (e.g. yield, water requirements, crop cycle duration) but also because it is a starch, and therefore requires depolymerization to obtain glucose prior to entering the fermentation reaction. Dry milling of corn is sufficient for fuel ethanol, but all non-fuel ethanol, including food grade ethanol, requires the more energy-intensive wet milling process in order to extract starch from the other components of the grain. For non-fuel ethanol, starch alone becomes the substrate for fermentation following enzymatic saccharification.
Even still, fermentation of starch results in a mess of byproducts including short chain fatty acids, esters, and aldehydes, which may impart undesirable aromas. Other byproducts of corn fermentation can pose more of a safety concern, including cyclic and aromatic compounds such as phenol, benzoic acid, and styrene. Hence, additional purification steps are required to remove water and other organic impurities. Because water and ethanol form an azeotropic mixture, the highest percentage of ethanol that can be achieved via distillation is 96.5%. Nor is distillation adequate for the removal of many other trace level impurities of similar boiling points, which may compromise the safety and the flavor of food grade ethanol. Subsequent purification techniques typically include adsorbents like activated carbon for the removal of organic contaminants. The purity of the food grade ethanol is verified using chromatography-mass spectrometry techniques.
It might be illuminating to compare our ultra-pure, food grade ethanol to another mixture of fermented and distilled chemicals: tequila. One of these substances is food grade, while the other is, by most definitions, actual food. Both contain ethanol, but only tequila contains a plethora of other chemicals, including methanol, nitrosamines, and furfural – all carcinogenic. Something to consider over your next glass of gasoline compound.
Taking ethanol quality beyond fuel grade: A review