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In this review, recent advances in the methods of pre-treatment of plant material for the extraction of secondary metabolites with high biological activity are presented. The correct preparation of the material for extraction is as important as the selection of the extraction method. This step should prevent the degradation of bioactive compounds as well as the development of fungi and bacteria. Currently, the methods of preparation are expected to modify the particles of the plant material in such a way that will contribute to the release of bioactive compounds loosely bonded to cell wall polymers. This review presents a wide range of methods of preparing plant material, including drying, freeze-drying, convection drying, microwave vacuum drying, enzymatic processes, and fermentation. The influence of the particular methods on the structure of plant material particles, the level of preserved bioactive compounds, and the possibility of their release during the extraction were highlighted. The plant material pre-treatment techniques used were discussed with respect to the amount of compounds released during extraction as well their application in various industries interested in products with a high content of biologically active compounds, such as the pharmaceutical, cosmetics, and food industries.

The success of mRNA vaccines against SARS-CoV-2 has prompted interest in mRNA-based pharmaceuticals due to their rapid production, adaptability, and safety. Despite these advantages, the inherent instability of mRNA and its rapid degradation in vivo underscores the need for an encapsulation system for the administration and delivery of RNA-based therapeutics. Lipid nanoparticles (LNPs) have proven the most robust and safest option for in vivo applications. However, the mid- to long-term storage of mRNA-LNPs still requires sub-zero temperatures along the entire chain of supply, highlighting the need to develop alternatives to improve mRNA vaccine stability under non-freezing conditions to facilitate logistics and distribution. Lyophilization presents itself as an effective alternative to prolong the shelf life of mRNA vaccines under refrigeration conditions, although a complex optimization of the process parameters is needed to maintain the integrity of the mRNA-LNPs. Recent studies have demonstrated the feasibility of freeze-drying LNPs, showing that lyophilized mRNA-LNPs retain activity and stability. However, long-term functional data remain limited. Herein, we focus on obtaining an optimized lyophilizable mRNA-LNP formulation through the careful selection of an optimal buffer and cryoprotectant and by tuning freeze-drying parameters. The results demonstrate that our optimized lyophilization process maintains LNP characteristics and functionality for over a year at refrigerated temperatures, offering a viable solution to the logistical hurdles of mRNA vaccine distribution.

Liposomes have been utilized as a drug delivery system to increase the bioavailability of drugs and to control the rate of drug release at the target site of action. However, the occurrence of self-aggregation, coalescence, flocculation and the precipitation of aqueous liposomes during formulation or storage can cause degradation of the vesicle structure, leading to the decomposition of liposomes. To increase the stability of liposomes, post-processing techniques have been applied as an additional process to liposomes after formulation to remove water and generate dry liposome particles with a higher stability and greater accessibility for drug administration in comparison with aqueous liposomes. This review covers the effect of these techniques including freeze drying, spray drying and spray freeze drying on the stability, physicochemical properties and drug encapsulation efficiency of dry liposomes. The parameters affecting the properties of liposomes during the drying process are also highlighted in this review. In addition, the impact of using a protective agent to overcome such limitations of each process is thoroughly discussed through various studies.

Freeze-drying, also known as lyophilization, is a process in which water in the form of ice under low pressure is removed from a material by sublimation. This process has found many applications for the production of high quality food and pharmaceuticals. The main steps of the freeze-drying process, such as the freezing of the product and primary and secondary drying, are described in this paper. The problems and mechanisms of each step of the freeze-drying process are also analyzed. The methods necessary for the selection of the primary and secondary end processes are characterized. The review contains a description of the effects of process conditions and the selected physical properties of freeze-dried materials, such as structural properties (shrinkage and density porosity), color, and texture. The study shows that little attention is given to the mechanical properties and texture of freeze-dried materials obtained from different conditions of the lyophilization process.

Vacuum freeze-drying of biological materials is one of the best methods of water removal, with final products of highest quality. The solid state of water during freeze-drying protects the primary structure and the shape of the products with minimal volume reduction. In addition, the lower temperatures in the process allow maximal nutrient and bioactive compound retention. This technique has been successfully applied to diverse biological materials, such as meats, coffee, juices, dairy products, cells, and bacteria, and is standard practice for penicillin, hormones, blood plasma, vitamin preparations, etc. Despite its many advantages, having four to ten times more energy requirements than regular hot air drying, freeze-drying has always been recognized as the most expensive process for manufacturing a dehydrated product. The application of the freeze-drying process to plant-based foods has been traditionally dedicated to the production of space shuttle goods, military or extreme-sport foodstuffs, and specialty foods such as coffee or spices. Recently, the market for ‘natural’ and ‘organic’ products is, however, strongly growing as well as the consumer’s demand for foods with minimal processing and high quality. From this perspective, the market for freeze-dried plant-based foods is not only increasing but also diversifying. Freeze-dried fruits and vegetables chunks, pieces, or slices are nowadays majorly used in a wide range of food products such as confectionaries, morning cereals, soups, bakeries, meal boxes, etc. Instant drinks are prepared out of freeze-dried tea, coffee, or even from maple syrup enriched with polyphenol concentrated extracts from trees. The possibilities are endless. In this review, the application of freeze-drying to transform plant-based foods was analyzed, based on the recent research publications on the subject and personal unpublished data. The review is structured around the following related topics: latest applications of freeze-drying to plant-based foods, specific technological problems that could be found when freeze-drying such products (i.e., presence of cuticle; high sugar or lipid concentration), pretreatments and intensification technologies employed in freeze-drying of plant-based foods, and quality issues of these freeze-dried products.

The current lyophilization technology for biopharmaceuticals and vaccine products is capital and energy-intensive, largely due to the use of indirect, conductive heat transfer. The heat removal and input in freezing, primary drying, and secondary drying are via contact between the product and shelves cooled or heated by a circulating working fluid such as silicone oil. This is slow, inefficient, and leads to non-uniform freezing and drying, especially in large-scale production systems. To address the current throughput limitations of conventional lyophilization, this collaborative project by Purdue University, Merck and IMA Life develops the next generation of tunable randomized-field microwave lyophilization system demonstrating significant acceleration over conventional freeze-drying processes. The system uses a microwave source delivering electromagnetic energy to the lyophilization chamber at frequencies between 8 GHz and 18 GHz at power levels below 400 W and mechanical stirrers for field randomization to achieve uniform heating. The frequency range is selected due to its greater efficiency for heating ice relative to traditional industrial microwave frequencies of 915 MHz and 2.45 GHz. During operation, temperature is measured directly using optical sensors, providing robust real-time product data. Closed-loop control algorithms enable direct control of the product temperature throughout the drying process, ensuring the material is dried at an optimal rate. The results of quasi-Random Field (qRF) microwave drying for several benchmark formulations, including an attenuated live virus vaccine, are presented and compared with the corresponding conventional lyophilization processes. A model for the product temperature and primary drying time is developed and validated against experimental cases.

Highly porous, lightweight versatile cellulose materials were prepared via dissolution–coagulation and subsequent various drying routes. Cellulose was dissolved in ionic liquid/DMSO mixture and coagulation was performed in ethanol. The as prepared wet precursors were used to make materials with three different drying methods: supercritical CO 2 drying, freeze-drying and vacuum drying. The influence of cellulose concentration and drying method on the density, porosity, specific surface area and morphology of cellulose materials is presented and discussed. We provide the understanding of morphology development as a function of processing conditions and give the “recipes” for porosity control.

PurposeInsomnia is a major health concern, and melatonin (MLT) is key for initiating sleep. Delivering MLT nasally can enhance brain bioavailability by targeting the olfactory region. This study aimed to fabricate MLT embedded microparticles for nasal delivery.MethodsMLT-cyclodextrin (CD) derivatives complex microparticles (MCCMPs) were fabricated by spray drying and spray freeze drying MLT and CD derivative solutions. Phase solubility and 1H-1H ROSEY NMR analysis assessed MLT-CD assembly. The effects of formulation compositions and process parameters on microparticle structural attributes were investigated. The in vitro nasal release and deposition performances were evaluated by a modified paddle-over-disk apparatus and 3D-printed nasal cavity cast, respectively.ResultsSodium sulphobutylether-β-cyclodextrin (SBE-β-CD) exhibited the best complexation ability with MLT, with the indole structure of MLT included in its cavity. Spray dried MCCMPs showed dense structure with high density, while the spray freeze dried counterpart showed the brittle and porous structure with low density. Despite the porous structure may promote the release rate of spray freeze dried samples, the high hydrophilicity of the CD derivative overshadows this advantage. Samples prepared by spray drying not only exhibited rapid release rates but also could deposit more effectively in the olfactory region, as they avoid breakage due to their higher mechanical strength. The optimal sample showed ~ 86.70% of the MLT released at 20 min and ~ 10.57% of the deposition fraction in the olfactory region.ConclusionsThis work compares MCCMPs fabricated by spray drying and spray freeze drying, providing the optimal formulation and process combinations.

Probiotics and prebiotics together work synergistically as synbiotics and confer various health benefits. Many studies on synbiotic foods only focus on the survival of probiotics but fail to evaluate their functional properties. The impact on functional properties should be explored to better understand its therapeutic efficacy. In this work, probiotics (Lactiplantibacillus plantarum NCIM 2083) were encapsulated with prebiotics (fructooligosaccharide + whey protein + maltodextrin) using spray-drying (SD), freeze-drying (FD), spray-freeze-drying (SFD), and refractance window-drying (RWD) techniques. Aggregation, intestinal adhesion, antagonistic activity, and bile salt hydrolase (BSH) activity of probiotics were studied before and after the encapsulation process. The SFD probiotics showed better aggregation ability (79% at 24-h incubation), on par with free cells (FC) (81% at 24-h incubation). The co-aggregation ability of encapsulated probiotics has drastic variations with each pathogenic strain. The adhesion ability of probiotics in chicken intestinal mucus was assessed by the crystal violet method, indicating no significant variations between FC and SFD probiotics. Also, encapsulated probiotics exhibit antagonistic activity (zone of inhibition in mm) against gut pathogens E. coli (11.33 to 17.34), S. faecalis (8.83 to 15.32), L. monocytogenes (13.67 to 18), S. boydii (12.17 to 15.5), and S. typhi (2.17 to 6.86). Overall, these studies confirm the significance and impact of various drying techniques on the functionality of encapsulated probiotics in synbiotic powders.Key points• Understanding the relevance of processing effects on the functionality of probiotics.• Spray-freeze-dried probiotics showed superior functional properties.• The encapsulation process had no significant impact on bile salt hydrolase activity.

Permanent preservation of genetic resources may be indispensable for the future of humanity. This requires liquid nitrogen, as is the case for preserving animal sperm. However, this technique is expensive and poses a risk of irrecoverable sample loss on non-replenishment of liquid nitrogen in case of natural disasters. In this study, we demonstrate that lyophilization may be used as a reliable method for long-term preservation of mouse sperm at room temperature. Sperm from four mouse strains were freeze-dried and stored in a non-temperature controlled room for 5–6 years. Although the ability of the stored sperm to activate oocytes had diminished slightly, healthy offspring were obtained by artificially activating the oocytes after sperm injection. Moreover, the birth rate did not decrease even after ≤ 6 years of storage. Furthermore, owing to its low cost, safety, and ease of storage at any location, we believe that this method could be a major mode of preserving mammalian genetic resources in the future.