By 10 a.m., the Richmond commercial kitchen that serves as a base for Mattersons Jamaican Cuisine is inundated with the aromas of chiles, thyme, allspice and grill smoke. Obrian Matterson, a slim 38-year-old whose vowels broaden and constrict depending on whether he’s talking to fellow Jamaicans or reporters, has already grilled off 180 legs of jerk chicken.

As he packs food into aluminum containers, his staff hustle around him, slicing plantains to deep-fry and pouring jerk sauce into containers. Half of the food will be carted onto Matterson’s food truck, Scotch Bonnet, destined for San Francisco’s Financial District. The other half is being driven to tech companies in the South Bay.

In San Francisco, the common wisdom has been that tech companies are bad for nearby restaurants because so many build luxe cafeterias to keep employees near their desks. And yet the culture of free food has allowed hundreds of small food operations like Matterson’s to thrive by providing lunches to the tech industry. It is not an underground economy, but a quiet one, invisible to the public and sometimes the workers they feed

Also growing is the number of brokers who connect cooks to offices — and take a cut of the profits. Most are based in the Bay Area and have attracted significant sums from venture capitalists: more than $20 million for Zesty, $16.5 million for Eat Club and close to $6 million for ZeroCater.

Two Bay Area companies, ZeroCater and Cater2Me, were the first to connect tech offices with local cooks and restaurants in 2010. Zach Yungst, who founded Cater2Me with Alex Lorton, came up with the idea of a n office-lunch concierge service after becoming dissatisfied with the watery soups and wilted salads provided by his former employer, a private-equity firm. Cater2Me sold companies on its ability to curate lunch, rotating cuisines so employees wouldn’t get bored. In the early days, he canvassed farmers’ markets and food trucks, looking for food businesses willing to prepare meals in a commercial kitchen and deliver them to corporate offices.

Obrian Matterson met Yungst through those scouting trips. Matterson had moved from Jamaica to the Bay Area a year earlier after marrying his American-born wife, Loris. The couple were cooking out of their home, but Cater2Me’s offer of legitimate catering work spurred them to take what they called “a crash course” in food business, getting the right paperwork and renting a commercial kitchen. The effort paid off. “We started out doing one job a day, and four weeks later, we were doing 30 to 35 jobs a week,” Obrian said.

The timing couldn’t have been more ideal for both sides. With billions of dollars gushing into Silicon Valley and San Francisco, Cater2Me and ZeroCater provided an easy-to-scale, flexible employee perk, and the two catering brokers amassed large stables of food businesses. By 2013, many of their food vendors worked for both competitors. There was enough work to go around.

“It’s like having a sales person, so we don’t have to worry about finding the business, pounding the pavement, dealing with the logistics,” said Brian Yee of City Smoke House. “We can just focus on the food.” The money has been good enough for Yee and his brother, Brandon, to take over a two-story commercial kitchen on Sixth Street in San Francisco, where their staff of seven smokes briskets and bakes poster-size pans of corn bread — without a storefront or a food truck.

The steady stream of income coming from corporate catering has allowed cooks to expand farther and faster than they could have on their own. Vive La Tarte’s owners, Arnaud Goethals and Julie Vandermeersch, emigrated from Brussels to San Francisco five years ago and began baking Belgian-inspired tartes and quiches. In the early days, 75 percent of their business was through brokers like Cater2Me and ZeroCater, Goethals said.

Eighteen months ago, Vive La Tarte was able to open an expansive, airy cafe in SoMa. Constructed with multiple income streams in mind, it has an espresso station, a long pastry case and a large production kitchen, because catering lunches and parties still brings in a third of Vive La Tarte’s revenue.

Cooking lunch for office workers comes with its challenges. “You don’t have a lot of leeway,” Goethals said. “If they tell you 12:30, you have to be there at 12:30.” Drivers who know how to set up the food properly are rare. Staying competitive with gluten-free crusts, vegan dishes and Paleo dishes has taken ingenuity.

Established restaurants have also seen the benefit of adding corporate catering. “Our food gets delivered by Zesty to downtown offices where we have no physical presence,” said Anjan Mitra of Dosa. Dosa prepares orders for Eat Club and Farm Hill, too, largely in its South San Francisco commissary or at its Valencia Street location, which isn’t open for lunch. “We just felt like it was a revenue opportunity for us in the daytime.”

In January 2015, a five-alarm fire shut down Los Shucos, Sofia Keck’s Guatemalan hot dog stand in the Mission. That’s when she discovered Cater2Me. Keck began prepping out of a commercial kitchen and assembling her elaborately garnished sausage sandwiches at companies around the region. When the repairs at Los Shucos were completed, she reopened with limited hours — mostly on the weekend — so she wouldn’t lose all her new catering clients.

Catering has always been a lucrative side business for restaurants. But the brokers who arrange for office lunches take a large cut — generally 15 to 30 percent. Food vendors rely on volume to make a profit.

That large cut is why Caleb Zigas, executive director of the San Francisco business incubator program La Cocina, is wary of the brokers. “They’ve certainly played a big role in the growth of the companies at La Cocina,” Zigas said. “What I keep pushing on our businesses is that (catering through brokers) has to be a temporary cash-flow situation until they can get themselves on their feet.”

“It’s a very dependent relationship,” he added. Cater2Me and ZeroCater require vendors to deliver and set up the food, establishing at least some personal interaction with the companies they serve. Newer companies like Zesty and Chewse handle all the delivery, eliminating the hassle but also the vendors’ exposure.

Binita Pradhan, owner of Bini’s Kitchen, laughed when asked about Zigas’ concerns. “The clients are super good. I feel blessed,” she said. Catering represents 40 to 50 percent of her business, but she also sells her momos (Nepalese dumplings) and curries to Whole Foods stores, operates a stand at Off the Grid’s Fort Mason event and, as of last year, runs a takeout restaurant in the Financial District. She has 16 employees.

Yet Zigas’ fear of overdependence may not just be professional paranoia. A number of food vendors have seen their catering income drop of late. After the Mattersons launched their food truck in 2014, funded by their catering earnings, Cater2Me and ZeroCater brought on additional Caribbean vendors and their orders shrank. Vive La Tarte and City Smoke House are also seeing decreasing orders, and both said their clients are spending less per person for lunch. “We indirectly have our finger on the pulse of the economy,” Brian Yee says.

Both Cater2Me and Zesty insist that their companies are growing, though they refused to provide specific metrics. Yungst claimed that in 2015, Cater2Me worked with 1,000 vendors in 11 cities. The average vendor sold $10,000 in food each month through the broker, and the higher-volume vendors could make up to $100,000 a month.

Back at the Richmond kitchen, Loris and Obrian Matterson are relishing the prospect of a winter slowdown after a busy summer juggling public festivals, food truck gatherings and office catering. It will give them some time to figure out what direction they will take next: A second food truck? A full-service restaurant?

Loris said that, despite the success of Scotch Bonnet, ZeroCater and Cater2Me still provide 35 to 40 percent of their gross sales. “It definitely helps pay the bills,” she said.

When aspiring chefs ask her whether they should buy a food truck or open a restaurant, she tells them to test the waters first. “A good way to see if your product is good is corporate catering,” she said. “It’s like an incremental step.”

Jonathan Kauffman is a San Francisco Chronicle staff writer. Email: jkauffman@sfchronicle.com Twitter: @jonkauffman