Two alternatives of computational models to simulate the contamination has been produced in the Mat Lab. The models are based on the transfer of bacteria between the hands, chicken, knife, cutting board, salad, and tap and also reduction of bacteria by washing the cutting board, and growth on cutting board. The input of the transmission, reduction and growth have been adopted on the basis of support from the literature data. In the simpler contamination model the contamination is only calculated in one direction. In the more complex model the transfer of bacteria that occurs from both sides at a touch has been taken into account, ie, if a person touch a cutting board, bacteria is transferred from the hand to the cutting board and also from the cutting board to the hand. Calculations were performed with matrix calculation. The results from the two models differ in the simulations. The more repeated contacts taken with the more bacteria spread from a contaminated hand at the start of the scenario to the final product. Models provide a guide to the factors in the spread of bacteria that are most important.