NEW YORK — In recent years, the alternatives to conventional cows’ milk have proliferated. The local grocery store is likely to offer any number of plant-based options: milks made from soy, almonds, oats, rice, hemp, coconuts, cashews, pea plants and more.

But most nondairy milks pale in comparison to cows’ milk. Plant-based milks are made by breaking down plants and reconstituting their proteins in water to resemble the fluid from a lactating bovine. These proteins differ fundamentally from true dairy proteins, and the results — milks, cheeses and yogurts in name only — often fail to measure up in color, taste or texture. Inja Radman, a molecular biologist and a founder of New Culture, a food company, put it plainly.

“Vegan cheese is just terrible,” she said. “As scientists, we know why it doesn’t work. It doesn’t have the crucial dairy proteins.”

Dairy tastes like dairy thanks to two key proteins, casein and whey protein. Researchers at several startup companies, including New Culture, have begun producing these proteins in the lab, with the aim of creating a new grocery store category: cow-free dairy.

Their process is loosely comparable to the way Impossible Foods or Beyond Meat makes meatless burgers. Microbes, such as yeast, are given the genetic instructions to produce the dairy proteins. The microbes are then cultivated en masse, with nutrients added and the temperature adjusted. Eventually the organisms start churning out large quantities of the proteins, and these are isolated and added to various recipes.

For the Impossible Burger, the essential protein is a molecule called heme, which is abundant in animal muscles and gives the burger its meaty flavor, and even makes it appear to bleed. New Culture is focusing on producing casein, a protein that coagulates to give mozzarella cheese its stretchy texture.

Ms Radman said the company had conducted double-blind tests to see if people could tell the difference between the proof-of-concept cheese and store-bought mozzarella. “We’ve had really positive results,” she said.

The quest for cow-free dairy is expanding. In Oakland, California, scientists at a community science lab are trying to make their own open-source recipe for lab-made cheese. And a startup in Boston called Motif Ingredients is engineering a variety of ingredients to replace traditional dairy, eggs and meat proteins.

Another company, Perfect Day (originally Muufri), may be the furthest along in perfecting a recipe for lab-made dairy. The company produces whey protein and mixes them with other ingredients found in traditional dairy — fats, carbohydrates, calcium and phosphates. In early July, a limited-edition batch was released, with flavors including chocolate, vanilla salted fudge and vanilla blackberry toffee; it quickly sold out.

Hundreds of thousands of metric tons of whey and casein are consumed in the United States each year, virtually all of it produced by dairy farms. Proponents of lab-made milk see the product appealing to dairy lovers broadly, while satisfying concerns about animal welfare and environmental sustainability. But to make a real impact on the planet, and eliminate the carbon emissions from all those belching cows, a great many microbes will need to be corralled.

The challenge is scaling up. Perfect Day plans to sell its lab-made whey to ice cream-makers, dairy companies and restaurants rather than directly to consumers. It has also partnered with agriculture giant Archer Daniels Midland, with its industrial-scale fermentation infrastructure, to try to meet market demand and reduce the cost of producing proteins.

“That’s what the two of us spend the most of our time on now,” said Perumal Ghandi, a founder of Perfect Day. “Sure, we have ADM, but even if we max them out, it’s still just a drop in the bucket.”

And there is already stiff competition from plant-based dairy alternatives, which offer similar environmental benefits and have gained popularity among consumers. Sales of plant-based milks jumped 6% last year, and now make up 13% of the entire milk category, according to data from the Plant Based Foods Association and The Good Food Institute. Sales of plant-based ice cream and frozen desserts grew 27%; plant-based cheese grew 19%, and plant-based yogurt grew 39%.

“All of a sudden people are realizing that they don’t have to depend on cows for milk,” said Cheryl Mitchell, head of research and development at Elmhurst 1925, once one of New York City’s largest dairy companies, which switched to making nut milks in 2017.

Technology has also improved the taste of plant-based milks and decreased the amount of water needed to produce several of them. “We want to be increasing our agricultural diversity to help environmental sustainability, not just relying on one source,” Ms Mitchell said.

Beyond Meat and Impossible Burger have been popular with consumers. Whether lab-made milk can replicate that success is an open question.

“What helped the Impossible Burger was their lab-made heme, which had a tremendous impact on both the flavor and visual appearance of the burger,” said Sam Alcaine, a food scientist at Cornell University. “I don’t know if lab-made dairy can make that leap and make consumers notice a difference in their dairy products.”

Labeling also has a big impact. The Food and Drug Administration has a legal standard for what can be called “ice cream,” Mr Alcaine said. Officially, ice cream must contain no less than 10% milk fat (or cream) from a cow. Perfect Day products have none; they contain coconut oil and sunflower oil instead, to remain animal-free, and must be labeled “frozen dairy dessert,” not “ice cream.”

Dairy farmers are also likely to push back, lobbying for stronger laws governing the labeling of lab-made products, as they have done for plant-based milks. Cattle ranchers have already introduced bills in 24 states that, if passed, would make it illegal to use the word “meat” to describe burgers and sausages made from plants or grown in labs.

But the founders of Perfect Day are not concerned. They say that their dairy products will prove more popular than plant-based alternatives, to vegans, vegetarians, dairy lovers and everyone in between.

“We’ve spoken to folks from dairy before,” said Ryan Pandya, a founder of Perfect Day. “By and large there’s a feeling that this could help, because there are so many consumers leaving dairy to consume plant alternatives, whereas we are making something that is still dairy at heart.” He added, “There’s an opportunity here for a whole new category of food.” THE NEW YORK TIMES