News

Comparative Study on Compaction and Sintering Behavior of Spray and Freeze Granulated Magnesium Aluminate Spinel Powder

Swathi Manivannan, Papiya Biswas, Prasenjit Barick, Sweety Kumari, Bhaskar Prasad Saha & Roy Johnson

Abstract

Commercially procured magnesium aluminate (MgAl2O4) spinel powder with average particle size of 300 nm and irregular morphology were spray and freeze granulated. The granules were characterized for the texture, strength, granule size and its distribution. In order to evaluate the flowability of granules, rheological parameters, such as Carr index and Hausner ratio were measured. The granules were further subjected to quasi-static compaction under loading, unloading conditions and compaction curves were constructed. Compaction coefficients thus obtained were correlated with granulation conditions and other parameters including green densities. Compacted green samples were also subjected to flexural strength measurements following ASTM standards and fractographs were observed under FESEM. A Carr index of 13.7 and Hausner ratio of 1.16 were obtained for freeze dried granules indicating the superiority in flow behavior as compared to its spray granulated counterpart, thereby showing a better compaction behavior: compaction coefficient of 5.9 in combination with higher true and predicted green density values and lower granule strength of 1.22 MPa. The green samples exhibited a flexural strength of 11 and 12.5 MPa and compressive strength of 2.44 and 1.22 MPa for spray and freeze granulated sample, respectively. The above observations were also complemented by the fractographs.

Keywords

Spray granulation, Freeze granulation, Spinel, Compaction curve

Morphology of alumina granules obtained by spray freeze drying with twin-fluid atomization

Ruslan Kuzmin, Sergey Veselov, Nina Cherkasova, Vladimir Bataev

Abstract

This study presents the results of the morphological dependence of alumina granules obtained by spray freeze drying (SFD) with twin-fluid atomization. It is shown that the introduction of 1-, 2- and 4-wt.% polyvinyl alcohol (PVA) as a binder in an alumina suspension leads to the formation of irregular granules. Depending on atomization conditions, spherical, “tadpole-like,” granule-satellite and granule aggregates may form during SFD. Increasing the flight time of droplets before the fixing of their shape when they come in contact with liquid nitrogen effectively contributes to the spheroidization of alumina granules. Compacting PVA-free SFD granules leads to the formation of diagonal flaws in a green-body structure. Adding PVA prevents the abovementioned defects by increasing the strength of alumina granules. Increasing the amount of PVA leads to an increase in “tadpole-like” granule content and, consequently, a decrease in a green-body density.

Combination of copigmentation and encapsulation strategies for the synergistic stabilization of anthocyanins

Chen Tan, Younas Dadmohammadi, Michelle C. Lee, Alireza Abbaspourrad

Abstract

Copigmentation and encapsulation are the two most commonly used techniques for anthocyanin stabilization. However, each of these techniques by itself suffers from many challenges associated with the simultaneous achievement of color intensification and high stability of anthocyanins. Integrating copigmentation and encapsulation may overcome the limitation of usage of a single technique. This review summarizes the most recent studies and their challenges aiming at combining copigmentation and encapsulation techniques. The effective approaches for encapsulating copigmented anthocyanins are described, including spray/freeze-drying, emulsification, gelation, polyelectrolyte complexation, and their combinations. Other emerging approaches, such as layer-by-layer deposition and ultrasonication, are also reviewed. The physicochemical principles underlying the combined strategies for the fabrication of various delivery systems are discussed. Particular emphasis is directed toward the synergistic effects of copigmentation and encapsulation, for example, modulating roles of copigments in the processes of gelation and complexation. Finally, some of the major challenges and opportunities for future studies are highlighted. The trend of integrating copigmentation and encapsulation has been just started to develop. The information in this review should facilitate the exploration of the combination of multistrategy and the fabrication of robust delivery systems for copigmented anthocyanins.

Effect of drying techniques on yield, nutritional, minerals of wild banana pulp (Musa balbisiana Colla): physicochemical and morphological characterization thereof

Twinkle Borah, Nooreen Washmin, Nayan Jyoti Bora, Jadumoni Saikia, Padma Sangmu Bomzon, Tobiul Hussain Ahmed, Prasenjit Manna, Siddhartha Proteem Saikia, Dipanwita Banik

Abstract

Purpose

The study was aimed to compare the effect of three drying techniques viz., spray, freeze and hot air oven (HAO) drying on yield, nutritional parameters, minerals and physicochemical and morphological characterization of wild banana pulp (Musa balbisiana Colla).

Design/methodology/approach

Contents of carbohydrate was estimated by Anthrone reagent, protein by Kjeldahl, fat by Soxhlet, dietary fiber and ash by Association of Official Analytical Chemists (AOAC), minerals by Atomic Absorption Spectrophotometry, gross calorific value by Bomb calorimeter, moisture by moisture analyzer, water activity by water activity meter, morphological characterization by Scanning Electron Microscopy (SEM), statistical level of significance at p < 0.05 by ANOVA, predictive modeling by simple and multiple linear regression.

Findings

Freeze and HAO drying were standardized with matured (stage 2) and spray drying with ripe bananas (stage 6). Freeze drying showed highest yield (76.69 ± 0.15%), minerals viz., K (1175.67 ± 1.41), Fe (2.27 ± 0.09), Mg (120.33 ± 0.47), Mn (4.40 ± 0.28) mg/100 g, protein (7.53 ± 0.14%), lesser moisture (7.95 ± 0.01%), water activity (0.17 ± 0.02aw), hygroscopicity (6.37 ± 1.09%), well dispersed particles by SEM. HAO drying exhibited highest dietary fiber (18.95 ± 0.24%), gross calorific value 357.17 kcal/100 gm, higher solubility (47.22 ± 0.86%). Spray drying showed highest carbohydrate (85.29 ± 0.01%), lowest yield (28.26 ± 0.32%), required 30.5% adjuncts.

Research limitations/implications

Effect of three drying techniques and use of adjuncts were not uniform for ripe and matured bananas.

Practical implications

Commercial utilization of seeded wild banana.

Social implications

Value addition of wild banana in Assam, India

Originality/value

Freeze drying of mature wild banana pulp (M. balbisiana) was found as best technique utilizing lesser energy.

Keywords

Musa balbisiana, Wild banana, Pulp, Powder, Spray, Oven, Freeze drying, Nutritional, Physicochemical

Thermolysis and Sensitivities of Nanometer Ammonium Nitrate Prepared by Ultra-low Temperature Spray Freeze Drying Method

Yi Wang, Xiaolan Song, Fengsheng Li

Abstract

Nanometer (nano) ammonium perchlorate (AP) and ammonium nitrate (AN) were prepared with 2D network structures by the ultra-low temperature spray method. Scanning electron microscopy (SEM), X-ray diffractometry (XRD), differential scanning calorimetry (DSC) and thermogravimetric analysis/infrared spectrometry (TG-IR) were employed to probe the micron structure, crystal phase, and thermal decomposition of nano AP and nano AN. SEM images revealed that the sizes of nano AP and AN were in the nanometer scale (<100 nm) in one dimension. XRD patterns showed that the crystal phases of nano AP and AN were in accordance with those of raw AP and raw AN, respectively. DSC traces indicated that the thermal decomposition process of AP depended on its particle size, while the thermolysis of AN was independent of the particle size of AN. TG-IR analyses illustrated that the decomposition products of nano AP were NO2, N2O, HCl and H2O, with a small amount of NOCl, and the main decomposition products of nano AN were N2O and H2O, with a small amount of NH3. The results of mechanical sensitivity tests indicated that nano AP was more sensitive than raw AP and both nano AN and raw AN were very insensitive to impact and friction stimuli.

Keywords

nano AP; nano AN; liquid nitrogen; freeze drying; thermolysis

Effects of Non-covalent Functionalization and Initial Mixing Methods on SWNT/PP and SWNT/EVOH Composites

Mahesh Parit, Virginia A. Davis

Abstract

We report that a simple, low-cost type of spray-freeze drying (SFD) significantly improves the dispersion of single-walled carbon nanotubes (SWNTs) in thermoplastic polymers. Conventional SFD requires costly specialized equipment and large amounts of material, both of which are impediments to laboratory research on nanomaterial composites. Our method uses more readily available equipment and can be adapted to use milligrams to grams of material. A household spray bottle containing an aqueous nanomaterial dispersion is used to spray the dispersion into a dish of liquid nitrogen. The resulting material is then lyophilized in a standard laboratory freeze dryer. The usefulness of this simplified method was explored by comparing the properties of polypropylene (PP) composites produced by this method to those produced by a previously reported rotary evaporation method in which the dispersion is vacuum-dried onto the polymer. The role of the initial dispersion state was explored by using pristine SWNTs as well as SWNTs stabilized by two common SWNT stabilizers: polyvinylpyrrolidone (PVP) and sodium dodecyl sulfate. Based on rheological, thermal, and morphological characterization, the porous friable structures produced by SFD resulted in better SWNT dispersion compared to composites produced by a previously reported rotary evaporation method. However, the PP/PVP-SWNT nanocomposites produced by both methods contained large aggregates. To verify that this aggregation behavior was the result of thermodynamic incompatibility between PP and PVP, ethylene vinyl alcohol (EVOH) nanocomposites containing PVP-SWNT were also produced using the SFD method. The results of this research show how a low-cost alternative to SFD along with careful consideration of compatibility is a promising approach to produce nanocomposites.

Keywords

Functionalization, Colloids, Nanocomposites, Carbon nanotubes, Polymers

Inhalable Protein Powder Prepared by Spray-Freeze-Drying Using Hydroxypropyl-β-Cyclodextrin as Excipient

Jason C. K. Lo, Harry W. Pan, Jenny K. W. Lam

Abstract

The prospect of inhaled biologics has garnered particular interest given the benefits of the pulmonary route of administration. Pertinent considerations in producing inhalable dry powders containing biological medicines relate to aerosol performance and protein stability. Spray-freeze-drying (SFD) has emerged as an established method to generate microparticles that can potentially be deposited in the lungs. Here, the SFD conditions and formulation composition were evaluated using bovine serum albumin (BSA) as a model protein and 2-hydroxypropyl-beta-cyclodextrin (HPβCD) as the protein stabilizer. A factorial design analysis was performed to investigate the effects of BSA content, solute concentration of feed solution, and atomization gas flow rate on dispersibility (as an emitted fraction), respirability (as fine particle fraction), particle size, and level of protein aggregation. The atomization gas flow rate was identified as a significant factor in influencing the aerosol performance of the powder formulations and protein aggregation. Nonetheless, high atomization gas flow rate induced aggregation, highlighting the need to further optimize the formulation. Of note, all the formulations exhibited excellent dispersibility, while no fragmentation of BSA occurred, indicating the feasibility of SFD and the promise of HPβCD as an excipient.

Keywords

Aerosolization, cyclodextrin, factorial design, inhalation, protein delivery, pulmonary delivery, spray-freeze-drying

Spray Freeze Drying: A novel process for the drying of foods and bioproducts

Padma Ishwarya S, Anandharamakrishnan Chinnaswamy, Andrew George Frederick Stapley

Abstract

Spray-freeze-drying (SFD) is an unconventional freeze drying technique that produces uniquely powdered products whilst still including the benefits of conventionally freeze dried products. SFD has potential applications in high value products due to its edge over other drying techniques in terms of product structure, quality, and the retention of volatiles and bioactive compounds. In cases where other drying techniques cannot provide these product attributes, SFD stands out despite the costs and complexities involved. This paper outlines the principles, methods, significant process parameters, particle morphology and quality aspects of SFD. Recent developments in this technique are reviewed including ultrasonic spray-freeze-drying, the application of computational fluid dynamics and mathematical modelling, and the incorporation of new technologies to improve product quality. In addition, the advantages, limitations and future scope for research in the field of SFD are discussed.

A meticulous overview on drying-based (spray-, freeze-, and spray-freeze) particle engineering approaches for pharmaceutical technologies

Abstract

Drying is an indispensable operation in the preparation of pharmaceutical powders and always remained one of the energetic tasks in the pharmaceutical industry. Improving the stability, solubility, and dissolution of pharmaceutical products are being prime objectives of the drying process, intending to produce the products loving the dry state. Although there are voluminous literatures available concerning drying operations, there is scant information available regarding the applicability of drying in drug delivery and process scale-up. The current communication embodies the different particle engineering technologies of drying viz. spray-, freeze-, and spray-freeze drying. In addition, potential uses of drying in the taste masking, and the development of inhalable powders presented briefly. Recent advancements in the drying of novel drug delivery systems is the major focus of the present review. In our opinion, the commercial aspects, regulatory guidelines, and scale-up strategies presented herein provide an opportunity to readers, researchers, and industrialists to ruin the critical issues during drying operations and aid in developing quality pharmaceutical technologies.

Keywords

Particle engineering, shell formation, spray drying, freeze drying, solubility, crystallinity

Development and validation of an asymptotic solution for a two-phase Stefan problem in a droplet subjected to convective boundary condition

Saad Akhtar, Minghan Xu, Agus P. Sasmito

Abstract

Droplet solidification is governed by classical Stefan problems which have been commonly treated as a single-phase problem by the majority of the studies in the literature. This approach, however, is unable to capture the initial temperature and the start of freezing time correctly. The treatment of two-phase Stefan problem in spherical coordinates is limited. No known exact solution exists, albeit numerical solutions and asymptotics have proven to be useful. We present a singular perturbation solution in the limit of low Stefan number and arbitrary Biot number for the two-phase Stefan problem in a finite spherical domain. An asymptotic solution is developed for a droplet at a non-freezing initial temperature subjected to a convective boundary condition at the surface. The solution is developed for both long-time and short-time scales. The results from asymptotic expansion method are validated with the experimental results in the literature and are further verified by a numerical model of a freezing droplet using enthalpy–porosity method. The sensitivity of the asymptotic solution to the droplet initial temperature, Biot number, and Stefan number has also been studied. The results indicate that the solution from perturbation series and enthalpy–porosity method agrees to within 1%–10% for temperature profile and overall freezing times over a wide range of practical values for initial temperature, Stefan and Biot numbers for the application of spray freezing. Our perturbation series solution is also able to capture the effect of initial temperature on the overall freezing time of the droplet.

Keywords

Perturbation series solution, Asymptotic expansion, Droplet freezing, Two-phase Stefan problem, Enthalpy–porosity method