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<p>Fouling is a severe problem for food processing equipment, including heat exchanger, filtration system, etc., which can decrease heat transfer efficiency, increase pressure drop, and affect food quality and safety. To ensure process efficiency and product quality, regular cleaning is necessary. On manufacturing lines in the food industry, cleaning is usually performed by cleaning-in-place (CIP) operations, which mainly comprise water rinse, alkaline wash and acid wash steps. Although CIP can ensure uniform cleaning of equipment, lower costs associated with labor and plant downtime, and improve personnel safety, it consumes large amounts of energy, chemicals and water and thus affects the environmental sustainability.</p>
<p>Microbubbles (MBs) are fine gas bubbles with very different physicochemical properties from millimeter-sized bubbles, including longer residence time in liquid, higher mass transfer rate, larger surface-area-to-volume ratio, and generation of free radical when bubbles collapse. In addition, MBs feature hydrophobic liquid-gas interface, allowing hydrophobic and amphipathic substances to attach to and spread on bubble surfaces. MBs have been used in cleaning processes, such as oil flotation and fresh produce washing; however, their applications in CIP operations in food processing have not been explored.</p>
<p>The objective of this dissertation is to develop a novel CIP operation with the incorporation of MBs for cleaning of food processing equipment. MBs were incorporated into rinsing water to clean milk deposit fouled on heat transfer surface. A computational fluid dynamics model was built to predict the contact frequency of MBs with deposit and further identify the flow conditions that provided maximum MB-deposit contact. Moreover, MBs were confirmed to be able to attach to milk deposit by microscopic imaging. Rinsing with MB-incorporated water noticeably enhanced the deposit removal at Re of 4392 and 5403, by 27−31%. For cleaning of microfiltration membrane reversibly fouled by palm oil-in-water emulsions as model wastewater, although adding MBs into alkaline wash increased the membrane flux recovery by 235%, increasing the crossflow velocity of MB-incorporated liquid did not guarantee the enhancement in cleaning performance. Lastly, a MB-assisted full CIP process was tested on an ultrafiltration system used for milk concentration. MB-assisted CIP showed an increased cleaning efficiency with up to 72% higher flux recovery than conventional CIP, and alkaline wash with MBs added was the major step accounting for enhanced protein removal.</p>
<p>Overall, this dissertation proves the effectiveness of MBs in cleaning of different types of food deposits, and provides groundwork knowledge of MB incorporation into CIP operations for different food processing equipment. The results are expected to guide the scale-up of MB-assisted CIP processes that can reduce the water and chemical usage in food manufacturing sectors, ultimately improving both economic and environmental sustainability of the food industry.</p>
| Identifer | oai:union.ndltd.org:purdue.edu/oai:figshare.com:article/21689336 |
| Date | 08 December 2022 |
| Creators | Monique Mi Song Chung (13943625) |
| Source Sets | Purdue University |
| Detected Language | English |
| Type | Text, Thesis |
| Rights | CC BY 4.0 |
| Relation | https://figshare.com/articles/thesis/Monique_Chung_Final_Dissertation_JYH_MCv2_pdf/21689336 |
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