THE CONTINUOUS MEASUREMENT OF SURFACE-WATER ACTIVITY IN DRY SAUSAGE

Dry sausage that are ripened for a long time undergo a drying process during bacterial fermentation (souring, aromatization) and during this drying process the moisture content of the sausages is reduced as evenly as possible. The ripening of dry sausage takes place, both industrially and on a small scale, in conditioning/smoking plant or in air conditioned storage rooms. In practice ripening is mostly controlled by random sampling. The sausages are sensorily evaluated for colour and appearance, the consistency of the sausages themselves and of the casings and for odour and flavour, but objective parameters such as weight loss, moisture content, pH and water activity (a(w)) are now increasingly being included. The bacteriological and physical changes that occur during fermentation can, however, only be considered schematically and stage by stage, given the time controls applied up to now. There are therefore often ripening faults because of the different qualitative and quantitative composition of the meat products. We therefore sought for possible ways of determining the surface water activity of sausages continuously. Our alm was to develop a method that would not be sensitive to disturbances and that could also be used as a building block for the control of ripening plant (providing a theoretical value for relative humidity). During the investigations it was found that it is possible, on the basis of thermodynamic laws, to determine the surface water activity of dry sausages continuously during ripening, having regard to the sausage temperature, the air temperature and the relative humidity of the ripening chamber. The method suggested is very uncomplicated, as only temperatures have to be measured. It can be used for the continuous control of ripening processes in existing conditioning plant and also as a building block for regulatory purposes in microprocessor controlled plant.