Sysco Boston LLC opened its 650,000-square-foot food distribution center last week. The building, which is located on 133 acres off Route 44 at the Spring Street interchange, is replacing the company’s Norton location. About 300 truckloads of inventory from that facility have been moved to Plympton, according to company officials. The global food-distribution company, which is advertising open positions on its website, syscobostonllc.com, will hold an open house with food samples in August.