Stability of Instant Coffee Foam by Nanobubbles Using Spray-Freeze Drying Technique

Stability of Instant Coffee Foam by Nanobubbles Using Spray-Freeze Drying Technique

Abstract

Instant coffee with stable foam is considered to be an important parameter for consumer preference and acceptability. For foam sustenance, nanoscale bubbles are more useful compared with microbubbles, due to their high specific area and high stagnation in the liquid phase (without undesirable liquid drainage). The technique that produces nanobubbles in coffee would concomitantly produce and preserve the coffee foam, the best. Spray-freeze drying (SFD) is known to be more effective for the production of instant coffee, compared with conventional spray drying (SD) and freeze drying (FD) techniques. However, its efficiency in the production of nanobubbles has not been explored. To address the issue, in the present study, SFD has been employed to produce instant coffee, and the findings have been compared with SD and FD. The coffee powder obtained with SFD produced a foam with higher stability that also comprised of nanobubbles, in contrast to SD and FD powders. The FE-SEM analysis of SFD foam showed the presence of nanobubbles in the range of 100–200 nm. When the beverage was prepared, the SFD coffee powder dissolved in water at 90 °C produced an excellent foam. The said foam structure was intact up to 2400 s (40 min), and lost only 89.5 ± 2 mm of foam height, during the experiment. Thus, apart from instant coffee, a stable foam in coffee comprising nanobubbles can also be achieved through the SFD.

Keywords

Spray-freeze drying, Nanobubbles, Coffee, Foam stability, Foam structure

Desalination of seawater by spray freezing in a natural draft tower

Desalination of seawater by spray freezing in a natural draft tower

YangLiu, TingzhenMing, YongjiaWu, Renaudde Richter, YuepingFang, NanZhou

Abstract

The freeze-melting process can be a viable method for the purposes of desalination because of its low energy consumption, ignorable corrosion issues, and without huge pressure or membrane replacement work. Large contact area for heat and mass transfer per unit mass of water between the water and air and low heat resistance results in higher energy efficiency during spray freezing desalination process compared to other freezing desalination methods. A 200 m high desalination tower was proposed in this paper that could generate 27.7 kg/s fresh water in the form of water droplets with 2 mm diameter at an atmospheric temperature of −26°C. This research has founded that the natural convective airflow induced by the heat released by the warm water in the freezing process could generate through the wind turbine mounted in this system approximately one-third of the energy consumed by the water pump of the system. This free energy has never been studied in previous research. The power consumption required to produce 1 m3 fresh water in this system is approximately 1.07 kWh. Compared to traditional desalination methods, the power consumption of our new spray freezing desalination system is much lower than previous systems with the same mass flow rate of fresh water. Only 375.4 kJ cold energy to produce one-kilogram fresh water. Thus, this spray freezing desalination system could be employed in desalination industry if free cold energy (e.g. from the cold atmosphere or the regasification process of LNG) and seawater resources are available.

Keywords

Compressible airflowNatural draft towerSeawater desalinationSpray freezingWater droplet

Sintering investigations of a UO2-PuO2 powder synthesized using the freeze-granulation route

Sintering investigations of a UO2-PuO2 powder synthesized using the freeze-granulation route

Marion Le Guellec, Florent Lebreton, Laure Ramond, Abibatou Ndiaye, Thierry Gervais, Guillaume Bernard-Granger

Abstract

Sintering investigations of a UO2-PuO2 powder, integrating 11 wt% of PuO2 and synthesized by freeze-granulation, were completed at temperatures up to 1700°C, in an atmosphere of Ar/4 vol% H2 and 1200 vpm H2O. Analyzing the “grain size versus relative density” trajectory enabled to propose that densification was controlled by volume diffusion and grain growth by the grain boundaries. An activation energy around 630 kJ/mol was obtained for densification, which was close to the value reported for volume diffusion of plutonium cations in U1-xPuxO2 polycrystals. The sintered microstructure appeared homogeneous regarding the plutonium and uranium cations distribution.

Keywords

Sintering, Ceramics, Oxides, Microstructure, MOX

Physicochemical changes of MTGase cross-linked surimi gels subjected to liquid nitrogen spray freezing

Physicochemical changes of MTGase cross-linked surimi gels subjected to liquid nitrogen spray freezing

Xiaoying Luo, Jinling Li, Wenli Yan, Ru Liu, Tao Yin, Juan You, Hongying Du, Shanbai Xiong, Yang Hu

Abstract

Physicochemical properties of microbial transglutaminase (MTGase) cross-linked surimi gels subjected to liquid nitrogen (LN) spray freezing with different temperatures and cross-linking degrees were investigated. Gels with lower LN spray temperature (−90 °C) were found taking less time in cooling down themselves to maximum-ice-crystal generating temperature. Microstructure images showed the pores of gels became smaller and the structure gradually became denser, as freezing temperature decreased and cross-linking degree increased. It also revealed T22 relaxation time of gels decreased significantly with surimi gels cross-linking degree increasing, indicating the binding ability of gels to moisture was enhanced accordingly. Meanwhile, the proton density weighted image brightness declined along with the LN spray temperature decreasing, and the image brightness showed a decreasing trend from outside to inside, indicating that water migrated and permeated easier from the inside of the gel network to the outside undergone higher LN temperature and lower cross-linking degree. Besides, the L and W values of LN groups decreased along with LN spray temperature and cross-linking degree increasing. Moreover, −90 °C LN group with 46.70% cross-linking degree presented the highest breaking force which ascribed to their synergistic efforts in maintaining a stable and dense structure of gels via controlling ice crystals and cross-linkages’ generation.

Keywords

Surimi gel, Cross-linking degree, Liquid nitrogen spray freezing

Effect of formulation and inhaler parameters on the dispersion of spray freeze dried voriconazole particles

Effect of formulation and inhaler parameters on the dispersion of spray freeze dried voriconazole particles

Qiuying Liao, Ivan C.H. Lam, Hinson H.S. Lin, Leon T.L. Wan, Jason C.K. Lo, Waiting Tai, Philip C.L. Kwok, Jenny K.W. Lam

Abstract

Spray freeze drying is a particle engineering technique that allows the production of porous particles of low density with excellent aerosol performance for inhalation. There are a number of operating parameters that can be manipulated in order to optimise the powder properties. In this study, a two-fluid nozzle was used to prepare spray freeze dried formulation of voriconazole, a triazole antifungal agent for the treatment of pulmonary aspergillosis. A full factorial design approach was adopted to explore the effects of drug concentration, atomisation gas flow rate and primary drying temperature. The aerosol performance of the spray freeze dried powder was evaluated using the next generation impactor (NGI) operated with different inhaler devices and flow rates. The results showed that the primary drying temperature played an important role in determining the aerosol properties of the powder. In general, the higher the primary drying temperature, the lower the emitted fraction (EF) and the higher the fine particle fraction (FPF). Formulations that contained the highest voriconazole concentration (80% w/w) and prepared at a high primary drying temperature (−10 °C) exhibited the best aerosol performance under different experimental conditions. The high concentration of the hydrophobic voriconazole reduced surface energy and cohesion, hence better powder dispersibility. The powders produced with higher primary drying temperature had a smaller particle size after dispersion and improved aerosol property, possibly due to the faster sublimation rate in the freeze-drying step that led to the formation of less aggregating or more fragile particles. Moreover, Breezhaler®, which has a low intrinsic resistance, was able to generate the best aerosol performance of the spray freeze dried voriconazole powders in terms of FPF.

Keywords

Aerosol performance, Antifungal agent, Factorial design, Freeze drying, Inhalation, Pulmonary delivery, Spray freeze drying

Evaluation of Process Conditions for Ultrasonic Spray-Freeze Drying of Transglutaminase

Evaluation of Process Conditions for Ultrasonic Spray-Freeze Drying of Transglutaminase

Hilal İşleroğlu, Izzet Turker

Abstract

In this study, a commercial transglutaminase enzyme was dried using an ultrasonic spray freeze drying method and the effects of the process conditions were optimized to maximize the final transglutaminase activity. Accordingly, process parameters affecting enzyme activity were selected, such as nozzle frequency (48 and 120 kHz), flow rate (2, 5 and 8 mL/min) and plate temperature for secondary drying (25, 35 and 45 °C). Moreover, the effects of different pH values (pH=2.0 and 9.0) and high temperature (80 °C) on enzyme activity, physical properties and particle morphology of transglutaminase were discussed. According to the results, transglutaminase preserved its activity despite ultrasonic spray freeze drying. Sonication enhanced the enzyme activity. Using the desirability function method, the optimum process conditions were determined to be flow rate 3.10 mL/min, plate temperature 45 °C and nozzle frequency 120 kHz. The predicted activity ratio was 1.17, and experimentally obtained ratio was 1.14±0.02. Furthermore, enzyme produced by ultrasonic spray freeze drying had low moisture values (2.92-4.36 %) at 8 h of drying. When the morphological structure of the transglutaminase particles produced by ultrasonic spray freeze drying under the optimum conditions was examined, spherical particles with pores on their surfaces were observed. In addition, flow properties of the transglutaminase powders were considered as fair under most conditions according to the Carr index.

Application of Spray Freeze Drying to Theophylline-Oxalic Acid Cocrystal Engineering for Inhaled Dry Powder Technology

Application of Spray Freeze Drying to Theophylline-Oxalic Acid Cocrystal Engineering for Inhaled Dry Powder Technology

Ryoma Tanaka, Yusuke Hattori, Makoto Otsuka, Kazuhide Ashizawa

Abstract

Spray freeze drying (SFD) produces suitable particles for the pharmaceutical formulation of dry powders used in dry powder inhalers (DPIs). However, SFD particles have large specific surface area and are partially made up of amorphous solids; this state is hygroscopic and would lead to changes in physicochemical properties by humidity when the particles are stored over the long-term or under high humidity conditions such as in the lungs. This study focused on the application of SFD with a cocrystal technique which can add humidity resistance to the active pharmaceutical ingredients (APIs), and the investigation of the physicochemical properties under high humidity conditions. Cocrystal samples containing theophylline anhydrate (THA) and oxalic acid (OXA) in a molar ratio of 2:1 were prepared by SFD. The crystalline structure, thermal behavior, solid-state, hygroscopicity, stability, and aerodynamic properties were evaluated. Simultaneous in situ measurement by near-infrared and Raman (NIR-Raman) spectroscopy was performed to analyze the humidification process. The SFD sample had a porous particle and an optimal aerodynamic particle size (3.03 μm) although the geometric particle diameter was 7.20 μm. In addition, the sample formed the THAOXA cocrystal with partial coamorphous. The hydration capacity and pseudopolymorphic transformation rate of the SFD sample were much lower than those of THA under conditions of 96.4% relative humidity and 40.0 °C temperature because of the cocrystal formation. The reasons were discussed based on the crystalline structure and energy. The SFD technology for cocrystallization would enable the pharmaceutical preparation of DPI products under environmentally friendly conditions.

Dense and homogeneous MOX fuel pellets manufactured using the freeze granulation route

Dense and homogeneous MOX fuel pellets manufactured using the freeze granulation route

F. La Lumia, L. Ramond, C. Pagnoux, P. Coste

Abstract

MOX fuels (UO2‐PuO2) are used in light water nuclear reactors of several countries and are also potential candidates for fast neutron reactors. Industrial MOX is currently manufactured by a dry‐route process, involving steps with fine powders. To reduce dusting, enhance MOX powder flow properties and decrease manufacturing scrap rate, a new wet‐route process is investigated: the freeze granulation of concentrated water‐based powder suspensions having optimized rheology and dispersion properties. Highly flowable, dustless and easy‐to‐press MOX granules have been elaborated. Sintering green compacts made of such granules gives highly dense and defect‐free pellets which have a very homogeneous U‐Pu spatial distribution, thus improving the fuel characteristics. Indeed, MOX fuels devoid of large Pu‐rich aggregates are thought to have a better behavior under irradiation in reactors by limiting/preventing the formation of the typical high burnup structure.

Rapid freezing using atomized liquid nitrogen spray followed by frozen storage below glass transition temperature for Cordyceps sinensis preservation: Quality attributes and storage stability

Rapid freezing using atomized liquid nitrogen spray followed by frozen storage below glass transition temperature for Cordyceps sinensis preservation: Quality attributes and storage stability

You Tian, Dongmei Li, Wenhuang Luo, Zhiwei Zhu, Wenjia Li, Zhengming Qian, Guangrong Li, Da-Wen Sun

Abstract

Fresh Cordyceps sinensis (CS) is rich in bioactive components but perishable with a short shelf-life and drying is the most common method for its preservation. For better retention of its quality and nutritional values, an innovative preservation technique using rapid freezing based on atomized liquid nitrogen (LN) spray followed by frozen storage below glass transition temperature (Tg) was developed in the current study. Atomized LN spray freezing of CS at −60 °C (LN-60), −80 °C (LN-80) and −100 °C (LN-100) was performed. Freezing rates and quality attributes of CS including electronic conductivity (EC), drip loss (DL), total sugar content (TSC), superoxide dismutase activity (ASOD), basic colour information (L*, a* and b* values) and total colour difference (ΔE) were investigated, and the stability of CS stored at −40 °C, which was below the Tg, for 16 weeks was evaluated. The Tg of CS was determined as −34.86 °C through differential scanning calorimeter (DSC) analysis. Multivariate data analyses including principal component analysis (PCA) and cluster analysis (CA) verified that LN-80 and LN-100 provided CS with better quality indicators, among which, ΔE, DL, and EC were the most predominant ones. The stability test suggested that LN-80 and LN-100 minimized the quality deterioration of CS during the frozen storage.

Keywords

Rapid freezing, Quality preservation, Multivariate data analysis, Principal component analysis, Cluster analysis

Binder Jetting Additive Manufacturing of Ceramics: Comparison of Flowability and Sinterability Between Raw and Granulated Powders

Binder Jetting Additive Manufacturing of Ceramics: Comparison of Flowability and Sinterability Between Raw and Granulated Powders

Wenchao Du, Guanxiong Miao, Lianlian Liu, Zhijian Pei, Chao Ma

Abstract

The objective of this study is to compare three different feedstock powders for the binder jetting process by characterizing their flowability and sinterability. Binder jetting additive manufacturing is a promising technology for fabricating ceramic parts with complex or customized geometries. Granulation is a promising material preparation method due to the potential high sinterability and flowability of the produced powder. However, no study has been made to systematically compare raw and granulated powders in terms of their flowing and sintering behaviors. This paper aims at filling this knowledge gap. Two raw powders (i.e., fine raw powder of 300 nm and coarse raw powder of 70 μm) and one granulated powder from spray freeze drying were compared. Different flowability metrics, including volumetric flow rate, mass flow rate, Hausner ratio, Carr index, and repose angle were measured. Different sinterability metrics, including sintered bulk density, volume shrinkage, and densification ratio were compared for all three powders. Results show that granulated powder achieved comparably high flowability to that of the coarse raw powder and also comparably high sinterability to that of the fine raw powder. Moreover, suitable metrics for the characterization of the sinterability and flowability for these three powders are recommended. This study suggests spray freeze drying produces high-quality feedstock powder for binder jetting process.

Keywords

Additive manufacturing, Binders (Materials), Ceramics, Drying, Feedstock, Flow (Dynamics), Sprays, Density, Materials preparation, Shrinkage (Materials), Sintering