<b>Novel Applications of Microbubble Technology for Sustainable Food Processing</b>
Creators: name: Bao, Yiwen
Publisher: name: Purdue University Graduate School
Year: 2024
Subjects: classificationCode: 300606
subject: Food sustainability
classificationCode: 300699
subject: Food sciences not elsewhere classified
classificationCode: 300604
subject: Food packaging, preservation and processing
classificationCode: 300607
subject: Food technology

description: Global food demand increases rapidly as a result of continuously growing population has raised severe concerns with food security. To overcome this critical challenge, food systems must be transformed to produce food with not only higher yield but also better nutritional quality. Therefore, food processing, as a critical step in food production chain that turn agricultural products into food, needs to be innovated through applications of cutting-edge technologies.Microbubbles (MBs) are tiny gas-filled bubbles with distinctive physicochemical characteristics, including slow rising speed and long lifetime in liquid, large surface area per unit of gas volume, high internal pressure, high gas dissolution rate, hydrophobic and negatively charged surface and production of reactive oxygen species. Additionally, MB dispersion can enhance the heat and mass transfer properties of liquid. These features have led MBs to numerous applications in the fields of disease treatment, anaerobic digestion, and wastewater treatment, however, their applications in food processing have not thoroughly explored.In this dissertation, MB technology was applied to different unit operations of food processing, including freezing, concentration and extraction, and the effects of MBs on process efficiency and food product quality were comprehensively studied. In the first study, MB-infused freezing medium was used for grape tomato immersion freezing. MBs markedly reduced the drip loss of tomato by 13.7–17.0% and improved its firmness, which were correlated to the accelerated nucleation process and formation of small ice crystals during freezing. The impact of MBs on water evaporation during apple juice concentration was investigated in the second study. MBs dramatically enhanced water evaporation, and concentration at bubble gas temperature of 40 °C and juice temperature of 70 °C showed the largest increase in the evaporation rate, by 104%. Moreover, although air-MBs showed an oxidation effect on both frozen tomato and concentrated juice, N<sub>2</sub>-MBs were found to be an ideal alternative which much better preserved the nutritional values of processed foods. Lastly, MBs and cold plasma-MBs were incorporated into citric acid solution for extracting pectin from apple pomace. MBs present in extracting solvent increased the extraction yield by 18–21%, and extraction with plasma-MBs showed even higher yields by up to 30%. Additionally, MB and cold plasma-assisted extraction were found more effective in extracting complex RG-I pectin.This dissertation develops various approaches to incorporating MBs into conventional unit operations and enhancing their performance. With these novel applications explored, MB technology will not only increase the productivity but also reduce the energy, water and chemical use of food processing. Ultimately, MB-assisted processes are expected to play an important role in improving the sustainability of the food industry.