Application of Micro- and Nano-Bubbles as a Tool to Improve the Rheological and Microstructural Properties of Formulated Greek-Style Yogurts

The objective of this study was to develop an alternative novel process technology for enhancing the rheological and functional properties of Greek-style yogurt (GSY). The GSY was formulated and prepared in the lab using micellar casein concentrate as a source of protein to achieve a protein content of 10% (w/w). The changes in physicochemical, microstructural, rheological, and functional properties of control (C-GSY) and micro- and nano-bubbles-treated GSY (MNB-GSY) were studied and compared before and after storage for 1, 2, 3, and 4 weeks. Before storage, the apparent viscosity at 100 s-1 (η100) was 1.09 Pa·s for C-GSY and 0.71 Pa·s for MNB-GSY. Incorporation of MNBs into GSY significantly (p < 0.05) decreased the η100 by 30% on 1 week of storage. Additionally, the η100 of MNB-GSY was lesser than C-GSY on week 2, 3, and 4 of storage. Notable microstructural changes and significant rheological differences were observed between the C-GSY and MNB-GSY samples. Differences were also noticed in syneresis, which was lower for the MNB-GSY compared with the control. Overall, the incorporation of MNBs into GSY showed considerable improvements in rheological and functional properties. Additionally, it's a simple, cost-effective process to implement in existing GSY production plants.

Effect of Microbubble Mixtures on the Washing Rate of Surfactant Solutions in a Swirling Flow and an Alternating Flow

Wastewater from laundry cleaning contributes to water pollution, and the amount of detergent used needs to be reduced. In the present study, water, four types of surfactants, and their microbubble mixtures were used, and washing rates were measured in swirling flows and alternating flows. The microbubble/water mixtures (average particle diameter: 25 μm; mixed with air at 1.5 vol % in water) achieved washing rates higher than those of water alone. Furthermore, microbubbles mixed with an aqueous surfactant solution had a washing rate that depended on the ionization of the surfactant: the mixtures with microbubbles and non-ionic and anionic surfactants had a washing rate that was higher than that of aqueous non-ionic and anionic surfactant solutions without microbubbles. The surface tensions of microbubble/water mixtures and mixtures of microbubbles with non-ionic and anionic surfactants were lower than those without microbubbles. These results provide evidence of an enhanced washing effect for microbubble mixtures in laundry cleaning.

Transmission electron microscopic observations of nanobubbles and their capture of impurities in wastewater

Unique properties of micro- and nanobubbles (MNBs), such as a high adsorption of impurities on their surface, are difficult to verify because MNBs are too small to observe directly. We thus used a transmission electron microscope (TEM) with the freeze-fractured replica method to observe oxygen (O2) MNBs in solutions. MNBs in pure water and in 1% NaCl solutions were spherical or oval. Their size distribution estimated from TEM images close to that of the original solution is measured by light-scattered methods. When we applied this technique to the observation of O2 MNBs formed in the wastewater of a sewage plant, we found the characteristic features of spherical MNBs that adsorbed surrounding impurity particles on their surface.PACS: 68.03.-g, 81.07.-b, 92.40.qc.