Sergey Brin, a co-founder of Google, appeared on a video shown at the event and announced that he funded the 250,000-euro ($330,000) project because of his concern for animal welfare.
"I would say it's close to meat. I miss the salt and pepper," said Austrian nutritionist Hanni Ruetzler, one of the volunteer tasters. Both shunned the bun and sliced tomatoes to concentrate on the meat.
"The absence is the fat, it's a leanness to it, but the bite feels like a conventional hamburger," said U.S. journalist Josh Schonwald. He added that he had rarely tasted a hambuger, as he did on Monday, "without ketchup or onions or jalapenos or bacon."
Monday's taste test, coming after five years of research, is a key step toward making lab meat a culinary phenomenon. Post called it "a good start."
Brin expressed high hopes for the technology.
"We're trying to create the first cultured beef hamburger. From there I'm optimistic we can really scale by leaps and bounds," he said on the video.
Post said it's crucial that the burger has the "look, feel and taste like the real thing."
Despite the tasters concern about flavor, scientists say that can be tweaked.
"Taste is the least (important) problem since this could be controlled by letting some of the stem cells develop into fat cells," said Stig Omholt, director of biotechnology at the Norwegian University of Life Sciences. Adding fat to the burgers this way would probably be healthier than getting it from naturally chunky cows, Omholt said before Monday's test. He was not involved in the project.
Post and colleagues made the meat from the muscle cells of two organic cows. The cells were put into a nutrient solution to help them develop into muscle tissue, growing into small strands of meat.
It took nearly 20,000 strands to make a single 140-gram (5-ounce) patty, which for Monday's taste test was seasoned with salt, egg powder, breadcrumbs, red beet juice and saffron.
"I'm a vegetarian, but I would be first in line to try this," said Jonathan Garlick, a stem cell researcher at Tufts University School of Dental Medicine in Boston. He has used similar techniques to make human skin but wasn't involved in the burger research.
Experts say new ways of producing meat are needed to satisfy growing carnivorous appetites without exhausting resources. By 2050, the Food and Agriculture Organization predicts global meat consumption will double as more people in developing countries can afford it. Raising animals destined for the dinner table takes up about 70 percent of all agricultural land.
The animal rights group PETA has thrown its support behind the lab-meat initiative.
"As long as there's anybody who's willing to kill a chicken, a cow or a pig to make their meal, we are all for this," said Ingrid Newkirk, PETA's president and co-founder. "Instead of the millions and billions (of animals) being slaughtered now, we could just clone a few cells to make burgers or chops."
Post and his colleagues had tasted the meat in the lab, and he said they cooked a test burger on Sunday.
"The first [lab-made] meat products are going to be very exclusive," said Isha Datar, director of New Harvest, an international nonprofit that promotes meat alternatives. "These burgers won't be in Happy Meals before someone rich and famous is eating them."
Only one patty was used for the taste test, and the testers each took less than half. Post said he would take the leftovers home and let his kids have a taste. Q&A on the science of growing hamburger in the lab
At a public tasting in London on Monday, Dutch scientists served hamburgers made from cow stem cells. Some questions and answers about the science behind the revolutionary patty.
Q: What are stem cells?
A: Stem cells are an organism's master cells and can be turned into any other cell type in the body, i.e. blood, tissue, muscle, etc.
Q: Why is the meat so expensive to produce?
A: The technology is new and scientists are making very small quantities of meat. There are no economies of scale to offset the initial high costs. If more scientists or companies start using the technology to produce more meat products, that could drop the price substantially.
Q: When could this meat be in stores?
A: Probably not for another 10 to 20 years. It would take years to refine the technology, encourage other producers and scientists to get involved, and overcome any regulatory issues.
Q: Who paid for the research?
A: Sergey Brin, co-founder of Google, underwrote the 250,000-euro ($330,000) project, which began in 2006.
Q: How is this better for the environment?
A: It could reduce the number of animals needed for the meat industry. Raising cows, pigs, chickens, etc. contributes substantially to climate change through the production of methane gas. Growing meat in the laboratory could reduce the impact on agricultural land, water and resources.
Q: How long does it take to grow a burger?
A: At the moment, a long time. It has taken two years for scientists to grow enough meat for two hamburgers. The research into the process started in 2006. Once there are enough strands of meat (about 20,000 small strands), scientists can form a five-ounce (140-gram) hamburger patty in about two hours.
Q: What are the implications for vegetarians?
A: PETA, People for the Ethical Treatment of Animals, supports attempts to grow meat in labs because they say that will greatly diminish the amount of animal suffering. Donor animals are needed for the muscle cells, but taking those samples doesn't hurt the animal. One sample can theoretically provide up to 20,000 tons of lab-made meat. But lab-grown meat is still meat, and not an option for vegetarians.
Q: Is it possible to make other kinds of meat in the laboratory?
A: Yes. The science is theoretically the same, so the same techniques should also allow researchers to make chicken, fish, lamb, etc. Dutch researcher Mark Post, who led the research on the lab-made hamburger, started working with pig cells. He had intended to make a sausage, but his American funder suggested a hamburger instead.
Q: Can they make other meat products?
A: At the moment, scientists are only working on making processed or minced meat, because that is the easiest kind to replicate. Processed meat accounts for about half of the meat market. Post said it should be possible to make more complicated cuts like steaks or chops in the future, but that involves using more advanced tissue engineering techniques. He estimates that it might be possible to make a steak in about 20 years.