A thin, blood-red liquid spilled out of the tasting spoon and into my mouth. It tasted of metal and, unsurprisingly, of blood.

I felt like I had been sucker punched, or had an unpleasant encounter with the dentist after not flossing for six months.

The culprit here is heme, a molecule found in most living things that carry oxygen through the bloodstream. It's also the secret ingredient in the fake meat from Impossible Foods.

In 2011, the Redwood City, California, startup set out on a mission to reinvent the veggie burger. While a black bean or mushroom patty probably isn't fooling anyone into thinking it's real meat, the Impossible Burger might. It sizzles on the grill, smells like beef, and even bleeds when you sink your teeth into it.

The experience is so authentic, the burger has been served by David Chang of the Momofuku empire and backed by Bill Gates and Google Ventures. In 2015, Impossible Foods declined a bid from Google to acquire the startup for between $200 and $300 million.

At a recent press event at the company's headquarters, I had the chance to try the meatless meat and its secret ingredient, heme.

A scientist at Impossible Foods tests varieties of heme, the secret ingredient in the Impossible Burger. Melia Robinson

In nature, heme gives blood its color, turns meat pink, and lends the traditional burger its slightly metallic flavor and delicious aroma when it's exposed to sugars and amino acids.

Impossible Foods looked into collecting it from the heme-rich nodules on soybean roots, but discovered it would require ripping up millions of plants to collect enough heme for production. Instead, the company decided to whip up heme in the lab. Scientists took the genetic code in soybeans that makes heme and injected it into yeast, which then becomes a temporary heme factory.

On the day of my visit, an Impossible Foods scientist showed me a small glass bowl full of the burgundy liquid. She invited me to try it. Sure, I thought. It's not every day you get to eat "plant blood."

My first spoonful would be my last.

The heme flooded my mouth and sealed my teeth, so that when I snacked later in the day, the new foods picked up a hint of blood. The after-taste stung like a papercut on the tongue, even though the inside of my mouth looked clean.

Raw heme? Not good.

But heme in the Impossible Foods burger might just leave the most ardent meat-lovers satisfied.

You can find the Impossible Burger at Nishi Momofuku in New York, Jardinière and Cockscomb in San Francisco, and Crossroads Kitchen in Los Angeles.