Microbubble-Assisted Cleaning To Enhance the Removal of Milk Deposits from the Heat Transfer Surface

Abstract

Cleaning is an important unit operation in food processing for removal of fouling deposits to ensure not only optimal operability of process equipment but also product safety and quality. In modern large-scale processing plants, cleaning is commonly achieved by cleaning-in-place (CIP) operation, which, however, consumes large amounts of water, energy, and chemicals. Because of their unique interfacial physicochemical properties, this study incorporated microbubbles (MBs) into water as a novel cleaning agent for the prerinse step of CIP operation, aiming to enhance its cleaning efficiency. MB-infused water (MB water) was introduced into bench-top spinning disc apparatus to clean milk deposits fouled on a stainless-steel surface. A computational fluid dynamics model was built to predict the contact frequency of MBs with deposits under swirl flow and further identify the cleaning conditions that provided maximum MB–deposit contact. MB–deposit attachment was visualized by microscopic imaging. A series of cleaning experiments were conducted at 25–55 °C and a Reynolds number (Re) of 3380–5403, and incorporation of MBs into water with 1431 bubbles/mL proved effective in increasing the cleaning efficiency at 25 °C and a Re of 4392 and 5403 by 27 and 31%, respectively. However, increasing water temperature and decreasing Re and bubble density were found to make the effect of MBs on cleaning insignificant. The findings of this study can serve as the groundwork for developing an MB-assisted CIP system to improve the environmental performance of food manufacturing.

Numerical investigation of oil droplet detachment from wall surface by a microbubble using ternary phase‐field model

“…Because the reflects the strength of the capillary interaction between the oil droplet and wall, the larger the contact angle, the weaker the interaction; thus, the oil droplet is easier to detach. Previous experimental studies have reported that degreasing with MBs is effective in systems with oleophobic substrates that have large contact angles, such as metal 20,23,26,28,29 and glass surfaces 21,27,30 . Owing to the few studies on oleophilic substrates, the tendency of oil droplet to detach only at the large contact angle of seems reasonable.…”

“…MBs is effective in systems with oleophobic substrates that have large contact angles, such as metal 20,23,26,28,29 and glass surfaces. 21,27,30 Owing to the few studies on oleophilic substrates, the tendency of oil droplet to detach only at the large contact angle of 140 seems reasonable.…”

“…Chung et al evaluated the effectiveness of MB water in cleaning milk deposits on a stainless steel surface. The flow field in the device was visualized by computational fluid dynamics (CFD), and it was shown that MBs made contact with oil at Reynolds numbers from 3380 to 5403 23 . Agarwal et al 24,25 and Li et al 26 cleaned sand contaminated with diesel oil by MBs.…”

Microbubble-Assisted Cleaning-in-Place Process for Ultrafiltration System and Its Environmental Performance

“…MBs have been reported to aid deposit removal by increasing momentum transfer due to bubble scrubbing [42] as well as energy released and shear flow generated by bubble collapse [24]. Moreover, in our previous study on MB-assisted cleaning of fouled heat transfer surface [21], MBs were observed to attach to milk foulant, resulting in enhanced removal. However, the spacer mesh placed to separate the two adjacent membranes and create the feed channel could limit the number of intact bubbles flowing across the spiral membrane, which can explain the insignificant improvement in flux recovery when increasing the bubble density in cleaning liquids.…”

“…MBs have been applied in various food-related areas, such as increasing soil removal from baby spinach during washing [17], promoting inactivation of Escherichia coli and Salmonella Typhimurium on leafy vegetables [18], enhancing salt diffusion into pork meat during brining [19], and intensifying yeast production [20]. Due to the hydrophobic surfaces, MBs have also proven effective in the cleaning of organic deposits and pollutants, including milk deposit removal from heat transfer surfaces [21], biofilm detachment from the membrane surface [22], food oil deposit removal from the microfiltration membrane [23], fouling reduction on the reverse osmosis membrane [24], and biodiesel removal from sand [25].…”