Scopus İndeksli Yayınlar Koleksiyonu / Scopus Indexed Publications Collection
Permanent URI for this collectionhttps://hdl.handle.net/11147/7148
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Article Lipid Monolayer Composition and Production Efficiency in DSPC/PEG40St Microbubbles for Ultrasound Applications(Elsevier, 2025) Kilic, Sevgi; Ozdemir, EkremLipid-coated microbubbles are widely used as ultrasound contrast agents (UCAs) and are being developed as carriers for drug and gene delivery. These microbubbles typically consist of an inert gas core and a stabilizing monolayer shell of phospholipid and a PEGylated emulsifier. In practice, a 9:1 M ratio of DSPC (a saturated phospholipid) to PEG-40-stearate (PEG40St) is conventionally used, under a long-standing assumption that the final composition of the microbubble shell is identical to the initial mixture composition. In this study, we tested that assumption over a wide range of DSPC/PEG40St ratios. Using sonication-based fabrication, we prepared microbubble suspensions with PEG40St fractions from 10 % up to 90 %. We then quantified the shell composition by proton nuclear magnetic resonance (1H NMR) and measured microbubble yield. Contrary to expectation, the PEG40St content in the bubble shells lower than PEG40St added, indicating selective exclusion or "squeezing out" of PEG40St during formation. Only about 4-6 % of the total lipid mixture ended up in the bubble shells and the rest remained as excess in the sub-phase. Thus, 94-96 % of the costly lipid/emulsifier was wasted in the production process. These results overturn the conventional assumption and highlight a critical inefficiency such that substantial amounts of lipid and PEG40St were lost during production, and the bubble yields were low. The findings have important implications for microbubble manufacturing, suggesting that alternative formulations or other production methods are needed to improve efficiency, and thus reduce costs.Article Citation - WoS: 69Citation - Scopus: 88Shelf Life Extension of Strawberry Juice by Equivalent Ultrasound, High Pressure, and Pulsed Electric Fields Processes(Elsevier, 2021) Yıldız, Semanur; Pokhrel, Prashant Raj; Ünlütürk, Sevcan; Barbosa-Canovas, Gustavo V.Nonthermal processing technologies have focused on the production of safe, fresh-like and high quality food products very much in line with current consumer demands. It is a high priority to maintain the quality attributes of the food during its shelf life. In this study; microbial stability, physicochemical properties and phytochemical characteristics of strawberry juice (SJ) pasteurized by ultrasonication (US) (55 degrees C, 0.29 W/mL acoustic energy density, 120 mu m amplitude, 3 min), high pressure processing (HPP) (300 MPa, 1 min), and pulsed electric fields (PEF) (35 kV/cm, 27 mu s) were evaluated during 42 days of storage at 4.C in comparison with conventional thermal pasteurization as a reference treatment (72 degrees C, 15 s). The nonthermal processes were equivalent in terms of E. coli inactivation since the selected processing conditions previously led to almost identical inactivation level (at least 5-log) of inoculated E. coli. Thus, the current study demonstrates how these equivalent US, HPP, and PEF treatments differ from each other in terms of their effect on SJ natural microbiota and quality characteristics during refrigerated storage. Results showed that US, HPP, and heat treatment ensured the microbial stability of SJ for at least 42 days while PEF extended the shelf life of SJ by at least 28 days based on the natural microbiota. No significant difference was found for the total soluble solids of the processed samples (p > 0.05) whereas acidity and pH of the samples varied during the storage period (p < 0.05). Immediately after processing, the total phenolic contents and antioxidant activities of SJ were better retained by HPP and PEF compared to thermal pasteurization. Furthermore, HPP and PEF significantly increased total anthocyanin content of SJ by 15 and 17% with respect to untreated SJ (p < 0.05). Phytochemical characteristics of processed SJ started to decrease after 7 days of storage irrespective of treatment type. HPP treated juices showed significantly higher levels of total anthocyanin and antioxidant activity at the final day of storage. Principal component and cluster analysis showed that the processed SJ samples had higher similarity to the untreated fresh SJ during storage up to 14 days, while the samples beyond this storage period clustered together and discriminated from the rest indicating a decreased similarity to the fresh juice. This study rendered simultaneous evaluation of several quality characteristics during storage of pasteurized strawberry juice based on the equivalent processing approach and multivariate data analysis. Under the selected processing conditions, HPP was the best option to extend the shelf life of SJ and enhance its phytochemical characteristics.Article Citation - WoS: 13Citation - Scopus: 17Effect of Ultrasound on the Kinetics of Cation Exchange in Nax Zeolite(Elsevier Ltd., 2012) Erten Kaya, Yasemin; Çakıcıoğlu Özkan, FehimeIn this study, we focused on the effect of ultrasound on ion exchange kinetics to obtain the Li-, Ca- and Ce-rich NaX zeolite. The results were compared to those obtained from the traditional batch exchange method under similar conditions. Contact time and initial cation concentration (fold equivalent excess) were studied. Ultrasound enhanced the replacement of Na + ion with Li +, Ca 2+ and Ce 3+ ions in the extra-framework of zeolite up to 76%, 72% and 66%, respectively. The intraparticle diffusion is the rate limiting step in the ion exchange for both exchange methods. As compared to the traditional exchange method, the ultrasonic method applied in this study was found to be very effective on the exchange amount at equilibrium.