After 17 years of making salsa, dips, spreads and burritos, Cobb's Corner Foods of Westford is calling it quits. "It was a really hard business to run," explains owner Rebecca Samanci. "I used to drive 10-hour days doing deliveries." Aside from the grueling hours, Samanci says, it was hard to make a buck with fresh, preservative-free offerings. "I was competing against [products with] three-month shelf lives. If it lasts three months, it's not food anymore," Samanci opines. She now works for Armistead Caregiver Services, her daughter's company, but isn't ruling out another food-related venture in the future. "I know an awful lot about the business . . . I'm waiting to see if something turns up."