It took Steve Demos nearly 30 years to find and fine-tune his cash cow product -- Silk soy milk -- now a staple of several Starbucks Corp. coffees and a noted early success of the organic-food movement. A Buddhist who once lived for several months in a cave in India, Mr. Demos struggled for decades to make soy, a product he describes as "weird," appetizing to the masses.

His answer finally came with milk, a familiar household product. And it catapulted Mr. Demos's company, WhiteWave Inc., into superstardom status in the food world -- and, ultimately, into the hands of dairy giant Dean Foods Co. DF +0.64% Dean Foods Co. U.S.: NYSE $14.91 +0.10 +0.64% March 17, 2014 9:48 am Volume (Delayed 15m) : 20,753 P/E Ratio 4.36 Market Cap $1.41 Billion Dividend Yield N/A Rev. per Employee $499,796 03/09/14 Asian Demand for Milk Shakes U... 02/12/14 Corrections & Amplifications 02/11/14 Dean Foods Reports Loss Amid H... More quote details and news » Dean invested in and later acquired the company in 2002, putting the market value of WhiteWave at $296 million. Mr. Demos left WhiteWave in 2005 and has since laid low under a noncompete agreement with Dean.

Until now.

In December, 58-year-old Mr. Demos began quietly shipping his latest food volley: GoodBelly, a line of stomach-soothing probiotic juice products aimed at aging baby boomers, which was created by his new company NextFoods Inc. Probiotics contain bacteria that are an essential part of a person's immune and digestive system.

In a few months, he has secured space nationally at Whole Foods Market Inc. and soon will be entering Safeway Inc. SWY -0.08% Safeway Inc. U.S.: NYSE $38.36 -0.03 -0.08% March 17, 2014 9:48 am Volume (Delayed 15m) : 48,441 P/E Ratio 2.65 Market Cap $8.85 Billion Dividend Yield 2.09% Rev. per Employee $261,878 03/13/14 Kroger Unveils $1 Billion Stoc... 03/10/14 Blackstone-Led Group Prepares ... 03/09/14 Deal Gives Safeway Scope to Th... More quote details and news » and H.E. Butt Grocery Co. in Texas. Mr. Demos says GoodBelly's fast, early traction stems from lessons learned during early missteps with Silk.

"I describe my career with WhiteWave as 20 years of hell and eight years of heaven," he says.

Here are excerpts from a recent interview with Mr. Demos:

Solutions Sell

The Wall Street Journal: You've said putting soy in milk took the "weirdness" out of the product. How do you keep GoodBelly from being weird?

Mr. Demos: There is risk in this. That's why we took common flavors [blueberry, mango and strawberry] and fruit it doesn't have the flavor resistance we had with soy.

There was a real stigma against the product with soy. It took 20 years to get there. We were trying to invent a new category. But once you've gotten there, you have key insights. One is "How many flavors of Milky Way did you eat when you were a kid?" The fact of the matter is [it was] one. You don't need a plethora of offerings. You need the right product with the right benefit in the right configuration.

With GoodBelly, our intent was to play to the convenience of the consumer who says, "Hey, I want to do something for myself that is good and I want to do it in a hurry."

WSJ: You've said the best new products find a problem to solve. Why is that?

Mr. Demos: The definition of a business is not a product. The definition of a business is a customer who is willing to give you money for something you have. And the only reason that a customer is going to give you money is because you solved some problem or offered them something that they don't already have. And if you can get to a biological need, you are going to have a continual supply of customers coming toward you.

WSJ: How does your new company meet a need?

Mr. Demos: Everybody is out-greening everybody else. So where is the future competitive advantage? It's going to be with science. NextFoods was the evolution out of the organic granola crunch world into the marriage of validated science and the natural order of food.

Deliberately Different

WSJ: For GoodBelly, you've licensed a strain of bacteria that aids digestion from a company in Sweden. Is that your competitive advantage?

Mr. Demos: There is some very deep, legitimate science on this bug. Its origins come from you. It is human. It is nontoxic, you can't overdose on it. If you re-establish these bugs in your gut, you will notice a digestive change.

So we started with this probiotic because it met all the criteria I just described -- not the least of which is the proprietary protection against somebody coming after us before we've had the chance to gain the first-move advantage with the consumer.

WSJ: Your first product is a 2.7-ounce "shot" of juice -- an unusual serving. Was that deliberate?

Mr. Demos: Absolutely. We have to establish our image as an innovator first.

WSJ: Will you be advertising?

Mr. Demos: We are doing guerrilla marketing...handing out a lot of products, creating buzz and just being present and bringing innovation and newness to the market. The market will always look for somebody who is willing to take the risk and put out something different.

And admittedly, we are using the "Hey, we were fairly talented with the Silk insights. Maybe we have the same mojo going with this one."

WSJ: Most of your top management team at NextFoods came from WhiteWave. Why pick the same team again?

Mr. Demos: I said if I am going to have half a chance of making this work, it won't be on the energy of a 58-year-old. It's going to be on the energy of those who are hungry professionals who already drank the Kool-Aid so to speak.

They had already been tested. As we all know in business, you are going to hit brick walls. You are going to need to fall back and know that they can close doors and have candid conversations and not be dancing around important issues in the first year. We accelerated the familiarity curve 10 years.

Profit First

WSJ: Your business has been carbon neutral from day one, but it's not something you put at the forefront of your message. Why not in this green era?

Mr. Demos: The first and foremost responsibility of a business is to make a profit so it is here tomorrow. You can't give something away unless you have it.

With that said, I earmarked a certain percentage of the money so we will be carbon neutral. We are organic in all the ingredients in the packaging. We are starting to work on the supply chain for biodegradable packaging. But again, I'm going to focus this team on making a profit before I start talking about where I'm going to give it away.

Write to Gwendolyn Bounds at