2.3. Storage test of Gouda cheese
Pre-sliced and packed Gouda cheese was cut to a size of 7 x 7 cm and inoculated with 1.8 x 10³ cfu/cm² of E. coli DSM 498 using a clean bench. Finally they were covered with the lacquered polyethylene-film. For reference samples, inoculated cheese slices were covered with the according lacquered polyethylene-film without sorbic acid. The cheese samples were stored in a sterile petri-dish at 8 °C up to 28 days. The count of E .coli was monitored as a function of time. After homogenizing the cheese with Ringer dissolution, the viable count of E .coli was determined by pour-plate method using violet red bile agar (VRB) after 0, 1, 3, 7, 14, 21 and 28 days of storage. Each inoculation and the colony count were done in triplicates.