Study of the preparation of a stable foam

Abstract: On a daily basis, abdominal examinations with x-ray imaging are run at hospitals for diagnosis of abdominal diseases. To enable doctors to visualize organs and tissues on an x-ray image with colors based on the radiodensity, the patient needs to drink an oral contrast that fills up the digestive system. Current filling agents have a radiodensity similar to that of organs and tissues which makes the contrast between the agent and the organs low, and a challenge for the doctor to give a correct diagnosis. The aim of this work was to scale down the production of a protein-based foam used as contrast agent, as the current process is not adapted to the time it takes for the patient to drink the full dose, leading to varying quality of the portions of foam swallowed. A production time of below 3 min was desired. Ultrasonication and scaling parameters of the current mixing method were evaluated for the mixing of powder ingredients in liquid (dispersion production). The foaming process was downscaled by evaluating equipment dimensions. Since the foam properties need to be unaffected by the downscaling, various analyses were conducted. Results from the ultrasonication experiments showed that ultrasound enhances foaming properties and decreases the bubble size to 1/3 of that obtained with the original method. Downscaling the dispersion production and foaming 3 downscaled dispersions according to the original foaming process resulted in foams that fulfilled the product requirements. However, when the same dispersion was foamed alone, the obtained foam did not fulfill the requirements. Increasing the dispersion mixing time and decreasing the foaming jar diameter resulted in downscaled foams with similar properties as the original foams. In vitro digestive treatments and an x-ray showed that the downscaled foams were acceptable but need slight improvement to eliminate visible bubbles. Downscaling the production resulted in foams indifferent from the original ones, but the time goal of 3 min production time was not accomplished since there seemed to be a minimum limit for the dispersion production essential for maintaining the foam properties. Increasing the foaming duration appeared to improve the stability of downscaled foams and needs to be further evaluated to eliminate the appearing visible bubbles.