Define Changes in Food due to Concentration Process?

Obviously concentration that exposes food to 100°C or higher temperatures for prolonged periods can cause major changes in organoleptic and nutritional properties. Cooking of foods and darkening of colour are two of the more common heat induced results, which should be kept under control throughout a well designed process with a well-organized evaporator which is still "safe". Microbial destruction is another type of change that may occur during concentration and will be largely dependent upon temperature. Concentration at a temperature of 100 °C or slightly above will kill many microorganisms but cannot be depended on to destroy bacterial spores. While the food consists of acid, like fruit juices, the extent of inactivation will be greater but again sterility is unlikely. On the other hand, when concentration is done under vacuum many bacterial types not only survive the low temperatures but also multiply in the concentrating equipment. It is therefore essential to stop often and sanitize low temperature evaporators and where sterile concentrated foods are needed, to resort to an extra preservation treatment.