Cleaning of ultra-high temperature milk fouling -Structural and compositionl changes

University dissertation from Department of Chemistry, Lund University

Abstract: Fouling is the deposit of proteins and minerals formed on equipment surfaces during the heat treatment of dairy products. The concentrations of the components and the structure of the fouling reflect the processing conditions used. The use of a higher processing temperature, e.g., ultra-high temperature (UHT) treatment, promotes a mineral-rich fouling. The fouling layer decreases the transfer of heat from the heating medium to the dairy product. A product that undergoes insufficient heating during processing may contain viable microorganisms, which spoil the product and can be hazardous to the consumer. Therefore, an efficient and cost-effective cleaning process is crucial for maintaining food safety, as well as for optimizing energy expenditure.
The main goal of this PhD thesis work has been to understand the fundamental mechanisms underlying cleaning for the removal of mineral-rich fouling, which to date has not been fully elucidated. The current investigations into the cleaning process, as well as the structure and chemical composition of the fouling layer reveal that the fouling of UHT processes has a high mineral concentration and low protein concentration. However, the proteins were found to be extensively interconnected with the fouling matrix and to play a crucial role in cleaning efficiency.
Cleaning is one of the major processes in the processing of dairy products. The cleaning has to be efficient, always resulting in a clean surface. It is crucial to remove the fouling from the heated surfaces. In this study, cleaning efficiency is shown to be affected by several parameters, such as temperature, alkali cleaning agent concentration, flow velocity, and time. The focus is on the alkali cleaning process, since the acid cleaning is shown to be a rapid process so the gains achieved through optimization of the process parameters are less impressive. Increasing the temperature and the concentration of cleaning agent is shown to have the largest effect on the depolymerization of the protein network within the mineral matrix and therefore has the greatest impact on cleaning efficiency.