April 5, 2012 | 23
Pink food seems to be raising a lot of eyebrows lately. A few weeks ago, meat product “pink slime” became embroiled in debate, and now a new crimson challenger has stolen the limelight: Starbucks has come under fire for using the pink dye cochineal (carmine) in their Strawberry Frappuccino drink (blogs including NPR’s The Salt and Bug Girl have also covered this story).
What’s the issue? Well, cochineal is made from…insects.
Public outcry suggests that Starbucks, searching for artificial dye replacements, secretly swapped cochineal into the drink. The whistleblower, though, was an anonymous barista, who identified the name on a nutrition label. Starbucks has stated that they’re “reviewing alternative natural ingredients” for their drinks. But, vegan activists wish to have the dye removed, and coffee shop regulars grow nauseous at the thought of consuming the colored drink. “This is the quintessential modern day P.R. crisis,” remarked a public relations rep in USA Today.
Insects on the Menu
Why are Frappuccino lovers so upset? Last I checked, tequila bottles still had worms swirling at the bottom, joke shops still sold lollipops with scorpions and flies embedded in candy “amber,” and the truly adventurous could purchase chocolate covered ants or grasshoppers online. School reading lists everywhere still recommend How to Eat Fried Worms to grade-schoolers.
As a culture, we dine on fancy-sounding bottom-feeders so frequently that we forget that they eat bugs, and other unmentionables. Catfish, lobster, crabs, frogs, crawfish – not to mention free-range chickens or turkeys – all subsist primarily on insects and waste materials. We clothe our bodies in silk made by worms, and most of the fruits we consume develop from flowers pollinated by flies, wasps, or bees.
Other cultures routinely supplement their protein intake with insects. A 2008 United Nations pamphlet, titled Edible Forest Insects: Humans Bite Back, lays out some of the species used as food in the Asia-Pacific region. Cooking insects, such as giant water bugs, crickets, June bugs, and cicadas, are “…deep-fried, grilled over an open fire, parched and ground, or steamed in banana leaves and curried.” In Thailand, it’s not uncommon to see food insects sold at roadside vendors, markets, or grocery stores. In other places, like Central America and Africa, locals consume various palm grubs and grasshoppers. Even the famously strict kosher dietary laws encourage eating certain types of locusts.
Attraction / Repulsion
So, back to strawberry drinks and crushed insects: why did the cochineal bug create its crimson? Better to ask why plants and animals evolve colors in the first place. Many natural colorants function in one of two ways: either to attract, say, for a symbiotic species or pollinator; or to repel, as a chemical defense mechanism against predators. Red coloring, like that found in maple leaves, poisonous amphibians, or certain snakes, transmits a distinct “Don’t Eat This!” warning. So, it shouldn’t surprise you that cochineal insects seem to have evolved their dye for similar reasons.
A team of researchers from Cornell and Ithaca Universities reported in Science (1980, 208, 1039-1042) confirmation of cochineal’s role as a chemical weapon against ants, one of their major predators. When the scientists doped sugary solutions with carmine, these treats were completely avoided by foraging ants. The paper also presented a unique twist to this story: carnivorous caterpillars that consume cochineal insects can later regurgitate their dye to ward off ant attackers.
Conjugation = Color
So, what does cochineal really look like? Like any dye, it has a chromophore (or “color bearer”), which generates its brilliant red color. Look over at the structure of cochineal (pictured, right). See how the three fused rings on the right have all those extra bonds in them? Dye molecules possess several conjugated bonds, alternating patterns of “single-double-single-double…” over long molecular distances. In general, the more bonds, the redder the color of the perceived (emitted) light, called a bathochromic or “red” shift. Beta-carotene, the familiar deep orange coloring found in sweet potatoes and carrots, illustrates this well, with 11 conjugated double bonds. Other highly conjugated compounds you’ve likely encountered include indigo (9 bonds), the dye in blue jeans, and curcumin (10 bonds), a bright yellow compound found in curry powder.
Another related ruby dye, used since ancient times, was alizarin, originally isolated from the madder plant. If you look at the structure (right, bottom), you’ll realize the two are very similar. In fact, both dyes derive from a chemical family called the anthroquinones, three-ringed compounds with two C=O (ketone) linkages in the center. Alizarin’s claim to fame goes back 150 years, when it became the first naturally-isolated dye to be prepared by lab synthesis. Mauve, a historical account of the dye business penned by Simon Garfield, relates the story well: in the 1870’s, companies in England and Germany waged an industrial war over competing dye manufacturing processes, a battle which would later spur such medical advances as tissue staining and photodynamic therapy.
Dye Processing – Removing the Bad Stuff
For those uncertain – you’re not really consuming “bug parts” when you chow on carmine. To prepare the dyestuff, chemists rely on two main processes: extraction and filtration. Extraction may seem familiar already – it’s the old saying “like dissolves like.” Certain compounds are more water soluble, while others find their solubility in fats and oils. In cochineal’s case, extraction might be better stated as “opposites attract:” a high pH (basic) solution of ammonia, calcium carbonate, or aluminum hydroxide is used to leach the red dye out of the crushed bodies. To be sure we’ve caught all the little chunks, we turn to filtration, which separates solids from liquids using porous surfaces like paper, sand, or cloth. Just like that, it’s exit, exoskeleton! Sayonara, scales! Arrivederci, antennae! The only part you’ll actually eat by day’s end is dye.
However, there might be tiny traces of hidden allergens lurking in there, because a few people report workplace asthma or a strong allergic reaction to bug-derived dyes. A recent patent (US2003/0199019) dealt with just this issue: researchers at Japanese firm San-Ei Gen treated crude cochineal extract with an enzyme called a protease to chop up problematic protein allergens, and later used a special adsorbent to wash away offending matter and further purify the dye.
Cochineal has been with us for centuries, and it’s already in food products. In fact, it’s usually labeled as an ingredient, and thus hidden in plain sight. Unless you’re among the few with allergic reactions, even to the protein-purified product, it’s probably just fine for you to consume.
To wrap up, I’ll relate another, more rational quote from the aforementioned USA Today piece, since it mirrors my exact thoughts on cochineal extract: “This is pretty far down on my list of outrageous food issues,” says Marion Nestle, a nutrition professor at NYU. Couldn’t have said it better myself.