Wood in Food – hygienic limits and cleaning procedures. Partial report 2

Summary

This work is a part of the project “Wood in the Food industry”, which have participants from all Nordic countries. The project is co-ordinated by the Norwegian Institute of Wood Technology and funded by the Nordic Wood. The aim of the present studies has been to study heat treatment of wood as a method to reduce the number of microorganisms to an acceptable hygienic level. The experiments are referring to activity no 4 and no 6 in the project; cleaning methods and hygienic limit values. Surfaces of wood were contaminated with either Halobacterium salinarum or microorganisms isolated from cod. The contaminated wood was then incubated at different time intervals and then heated at different temperatures and time intervals. The recovery of microbes after heat treatment was measured using both the swabbing and the contact method. The experiments show that heating can be used as a method to reduce the number of microorganisms on a wooden surface to an acceptable level. The required heating conditions (temperature, time) differ depending on the microorganisms present in the product and environment. Moist heat has better penetrating power than dry heat and causes a faster reduction of the number of living organisms at a given temperature. It seems that the time of incubation of the contaminated sample before the heat treatment is of vital importance to the detection of the microorganisms.