A young Mumbai couple have taken the city's most popular snack vada pav (potato burger) and transformed it into a fast-growing business.

Their model is none other than the world's fast-food king McDonald's.

Reeta and Dheeraj Gupta, founders of the Jumbo King chain, studied several restaurant companies, including McDonald's Corp, before setting up their first potato burger shop outside a suburban Mumbai railway station in 2001.

For years, street vendors have been selling vada pavs spicy fried potato patties slipped inside a bun from handcarts in Mumbai.

But the Guptas figured people would line up to eat the burgers from a proper shop where employees wear disposable gloves, ingredients are delivered in refrigerated containers from a central kitchen and spot checks are routine.

Four years later, their investment of Rs200,000 (Dh16,429) has spawned a 16-store chain that in the year through March 2005 had sales of Rs25 million (Dh2,040,887), and they project sales of Rs80 million (Dh6.2 million).

Doing research over the internet and poring over management books, the Guptas said McDonald's kept coming out on top in its supply chain management, quality control systems as well as maintaining hygiene in the restaurants.

"McDonald's is like the guru of fast food," Reeta Gupta, 29, the company's director, said in an interview. "Why reinvent the wheel? We've learned from them."

Her husband, Dheeraj, 31, even cleaned and scrubbed trays in a Mumbai McDonald's outlet for a week to get an inside look at how the restaurant operated.

In talking with employees, he found that many stayed with the company because of its regular system of promotions that allowed cleaners to eventually become managers.

Jumbo King does not compete directly with McDonald's, which opened its first restaurants in India in 1996 the first of the chain's outlets in the world with no beef on the menu because cows are sacred to India's Hindu majority.

With McDonald's basic potato and chicken burgers priced at Rs20 (Dh1.6) and up, the Golden Arches remain out of reach for most of India's 1 billion people, 80 per cent of whom are estimated to live on less than US$2 (Dh7.3) a day.

That's where the Guptas saw an opening to attract the masses by offering the cheap and popular potato patties from clean, well-stocked restaurants.

"We're targeting another set of people I'm concentrating on my Rs5 (40 fil) customer, the common man," Reeta said.

A standard spicy Jumbo King potato burger with an onion slice and garlic sauce costs Rs5. For a little extra, customers can have theirs on brown bread or with cheese. Garlic powder and tamarind chutney are thrown in for free.

To keep overheads down, Jumbo King's stores aren't air-conditioned and there are no seats. Customers also have to listen to loud ads blared over speakers: "Bring your family along. Eat Jumbo King the king of vada pavs!"

The Guptas' formula has proved remarkably popular, and Jumbo King's yellow and blue signs topped with a perky crown now command loyalty in Mumbai, India's financial capital.

But nutritionists warn that Jumbo King, like McDonald's, isn't exactly healthy food.

"This sort of food takes energy from the body instead of supplying energy," said Vijaya Venkat, who runs a popular Health Awareness Centre in Mumbai that conducts workshops on organic and natural food.

"Given a choice, people should eat fresh food like fruits and vegetables. All fried food is obnoxious food," she says. "Frying kills nutrition and makes it a foodless food."

Still, some 35,000 people each day pack into the chain's outlets, all located outside Mumbai's railway stations.

Among their most loyal customers are labourers who earn Rs40 (Dh3.2) a day, hip college students and even business executives who send their chafferers to pick up bags bursting with burgers.

Reeta said her true target customers are people like Ghansham Patel, a 59-year-old farmer from neighbouring Gujarat state who brings his family of six to Jumbo King when they are in Mumbai.

"The taste is good, and I don't have to worry about the children falling sick," he said as he munched on a burger.