Search Results (218)

This study describes both experimental and numerical investigations into the heat and mass transfer processes governing the vacuum freeze drying of camel milk, with a specific focus on improving the energy efficiency. A three-dimensional model was developed and solved using the finite element method to simulate temperature evolution and sublimation interface progression during drying. The numerical model was validated against experimental data, achieving strong agreement, with an $R^2$ value of 0.94. A detailed parametric analysis examined the effects of the shelf temperature, sample thickness, and chamber pressure on the drying kinetics and energy input. The results indicate that optimising these parameters can significantly reduce the energy consumption and processing time while maintaining product quality. Notably, reducing the sample thickness to 4 mm shortened the drying time by up to 40% and reduced the specific energy consumption (SEC) from 358 to 149 kWh/kg. These findings offer valuable insights for the design of more energy-efficient freeze drying systems, with implications for sustainable milk powder production and industrial-scale process optimisation. Full article

The efficient use of renewable lignocellulosic biomass has attracted wide interest, as it promises to reduce the environmental impact of fossil fuel consumption. A recently developed batch-scale process, which produces glycol lignin (GL) from softwood biomass, generates a considerable amount of cellulose-rich solid residues (SRs) as a byproduct. In this study, usable cellulose was isolated from SRs in the form of carboxylated cellulose nanocrystals (O-CNCs). The properties of O-CNCs were investigated to establish a possible integrated biomass utilization system based on the GL production technology. Three different forms of purified SRs—never-dried (N-Cel), freeze-dried (F-Cel), and vacuum-dried (V-Cel) cellulose—were subjected to oxalic acid (OA) hydrolysis at 95 °C for 4 h. The average length of O-CNCs ranged from 90 to 120 nm and the height ranged from 3 to 6 nm for separate particles and from 8 to 20 nm for aggregates. The carboxyl group content was 0.11–0.23 mmol/g O-CNCs. The overall results indicated that the yields, dimensions, surface charges, and thermal stability of the O-CNCs were largely influenced by the nature of the starting cellulose. In addition, O-CNCs prepared from recycled OA exhibited similar properties to those prepared from fresh OA. Full article

Grain drying technology is a core process for ensuring food quality, extending storage life, and improving processing adaptability. With the continuous growth of global food demand and the increasing requirements for food quality and energy efficiency, traditional drying technologies face multiple challenges. This paper reviews six major grain drying technologies, comprising hot air drying, microwave drying, infrared drying, freeze drying, vacuum drying, and solar drying. It provides an in-depth discussion of the working principles, advantages, and limitations of each technology, and analyzes their performance in practical applications. In response to challenges such as high energy consumption, uneven drying, and quality loss during the drying process, the paper also explores the research progress of several hybrid drying systems, such as microwave–hot air drying combined systems and solar–infrared drying systems. Although these emerging technologies show significant potential in improving drying efficiency, energy saving, and maintaining food quality, their high costs, scalability, and process stability still limit large-scale applications. Therefore, future research should focus on reducing energy consumption, improving drying precision, and optimizing drying system integration, particularly by introducing intelligent control systems. This would maximize the preservation of food quality while improving the system’s economic efficiency and sustainability, promoting innovation in food production and processing technologies, and further advancing global food security and sustainable agricultural development. Full article

Ammonia borane (AB), with a theoretical hydrogen content of 19.6 wt%, is constrained by its low crystalline density (0.758 g/cm³) and poor thermal stability (decomposing at 100 °C). In this study, AB/ammonium perchlorate (AP) composites were synthesized via freeze-drying at a 1:1 molar ratio. The integration of AP introduced intermolecular interactions that suppressed AB decomposition, increasing the onset temperature by 80 °C. Subsequent vacuum calcination at 100 °C for 2 h formed oxygen/fuel-integrated ammonium perchlorate borane (APB), which achieved decomposition temperatures exceeding 350 °C. The proposed mechanism involved AB decomposing into borazine and BN polymers at 100 °C, which then NH₃BH₂⁺/ClO₄⁻ combined to form APB. At 350 °C, APB underwent the following redox reactions: 4NH₃BH₂ClO₄ → N₂↑ + 4HCl↑ + 2B₂O₃ + N₂O↑ + O₂↑ + 7H₂O↑ + H₂↑, while residual AP decomposed. The composite exhibited improved density (1.66 g/cm³) and generated H₂, N₂, O_2, and HCl, demonstrating potential for hydrogen storage. Additionally, safety was enhanced by the suppression of AB’s exothermic decomposition (100–200 °C). APB, with its high energy density and thermal stability, was identified as a promising high-energy additive for high-burning-rate propellants. Full article

This study aims to identify the chemical structure and immunomodulatory activity of exopolysaccharides (EPSs) from Acetilactobacillus jinshanensis BJ01 and suggest its potential applications in the pharmaceutical field and as functional food additives. The EPS-1 produced by A. jinshanensis BJ01 was purified using column chromatography. The lyophilized powder obtained by vacuum freeze-drying was used for structural characterization and immunomodulatory activity analysis. Gel permeation chromatography (GPC) determined its molecular weight as 156.58 kDa. High-performance anion-exchange chromatography (HPAEC) identified that the EPS-1 is composed of mannose, xylose, and glucose. The structural characterization of EPS-1 by gas chromatography–mass spectrometry (GC-MS) and 1D/2D nuclear magnetic resonance (NMR) spectroscopy demonstrated that EPS-1 is primarily composed of α-D-Manp-(1→, →2,6)-α-D-Manp-(1→, →2)-α-D-Manp-(1→, and →3)-α-D-Manp-(1→. Scanning electron microscopy (SEM) and atomic force microscopy (AFM) illustrated that EPS-1 exhibited a round, flake-like morphology. In vitro experiments with RAW264.7 macrophages demonstrated the high immunomodulatory activity of EPS-1. Significant upregulation of iNOS, IL-6, and TNF-α mRNA levels was confirmed by qRT-PCR (p < 0.05). Western blotting revealed that EPS-1 (6.25 μg/mL) induced phosphorylation of NF-κB (p65, IκBα) and MAPK (ERK) signaling proteins. This study provides the first structural and immunomodulatory characterization of an exopolysaccharide from A. jinshanensis BJ01, highlighting its potential as a novel immune adjuvant. Full article

Drying constitutes an essential step in aerogel fabrication, where the drying method directly determines the pore structure and consequently influences the material’s functionality. This study employed various drying techniques to prepare balsa-wood-derived aerogels, systematically investigating their effects on microstructure, density, and performance characteristics. The results demonstrate that different drying methods regulate aerogels through distinct pore structure modifications. Supercritical CO₂ drying optimally preserves the native wood microstructure, yielding aerogels with superior thermal insulation performance. Freeze-drying induces the formation of ice crystals, which reconstructs the microstructure, resulting in aerogels with minimal density, significantly enhanced permeability, and exceptional cyclic water absorption capacity. Vacuum drying, oven drying, and natural drying all lead to significant deformation of the aerogel pore structure. Among them, oven drying increases the pore quantity of aerogels through volumetric contraction, thereby achieving the highest specific surface area. However, aerogels prepared by air drying have the highest density and the poorest thermal insulation performance. This study demonstrates that precise control of liquid surface tension during drying can effectively regulate both the pore architecture and functional performance of wood-derived aerogels. The findings offer fundamental insights into tailoring aerogel properties through optimized drying processes, providing valuable guidance for material design and application development. Full article

Yak meat jerky, a traditional high-protein food commonly consumed in high-altitude regions, is often produced via air-drying, which may adversely affect its nutritional quality and digestibility. This study systematically compared the gastrointestinal digestion profiles of air-dried yak meat (ADM) and vacuum freeze-dried yak meat (VFDM) using a dynamic in vitro human stomach–intestine (DHSI-IV) system. Key digestive parameters, including gastric emptying kinetics, particle size distribution, and protein hydrolysis, were evaluated under physiologically relevant conditions. VFDM exhibited superior hydration capacity, contributing to delayed gastric emptying of the mixed solid–liquid phase (t_1/2 = 85.1 ± 1.0 min) compared to ADM (t_1/2 = 80.4 ± 1.2 min), indicating increased gastric satiety. Conversely, VFDM showed a faster solid-phase gastric emptying (t_1/2 = 107.2 ± 0.8 min) relative to ADM (t_1/2 = 113.1 ± 2.7 min), likely due to improved texture and rehydration. Both jerky types exhibited progressive particle disintegration; by 180 min, large particles (>2.0 mm) decreased to 16.88% ± 2.63% in ADM and 20.04% ± 0.64% in VFDM (p > 0.05). Protein digestibility, measured by SDS-PAGE and the degree of hydrolysis (DH), was significantly higher in VFDM (38.5 ± 3.6%) than in ADM (34.0 ± 0.1%, p < 0.05), with VFDM demonstrating more rapid and extensive protein degradation across gastric and intestinal phases. These improvements may be attributed to the porous microstructure and reduced processing-induced protein cross-linking in VFDM, facilitating enhanced enzyme access. Overall, vacuum freeze-drying substantially improved yak jerky protein digestibility, offering the potential for the development of meat-based functional foods targeted at individuals with compromised gastrointestinal function. Full article

The purpose of this study was to investigate the effect of different drying methods on the structure and properties of semicrystalline polymer aerogels. Aerogels, consisting of either globular or strut-like morphologies, were prepared from poly(ether ether ketone) (PEEK) or poly(phenylene sulfide) (PPS) and dried using vacuum drying, freeze-drying, or supercritical CO₂ extraction. Vacuum drying was found to result in aerogels with a higher shrinkage, smaller mesopores (with pore widths of 2–50 nm), and smaller surface areas compared to the use of supercritical extraction as the drying method. Freeze-dried aerogels tended to have properties between those of vacuum-dried aerogels and aerogels prepared with supercritical extraction. High network connectivity was found to lead to improved gel modulus, which increased the ability of aerogels to resist network deformation due to stresses induced during drying. The PEEK and PPS aerogel networks consisting of highly connected strut-like features were considerably stiffer than those composed of globular features, and thus shrank less under the forces induced by vacuum drying or freeze-drying. The aerogels prepared from PPS were found to have larger mesopores and smaller surface areas than the aerogels prepared from PEEK. The larger mesopores of the PPS aerogels induced lower capillary stresses on the aerogel network, and thus shrank less. This work demonstrates that preparing PEEK and PPS gels with strut-like features can allow aerogel processing with simpler evaporative drying methods rather than the more complex supercritical drying method. Full article

This study aims to examine the effects of various drying methods, namely convective drying (CD), vacuum drying (VD), infrared drying (IRD), low-temperature vacuum drying (LTVD), and freeze-drying (FD), on the microstructure and in vitro bioaccessibility of red cabbage bioactive compounds and antioxidant activity. Total polyphenol content (TPC), total flavonoid content (TFC), total anthocyanin content (TAC), total glucosinolate content (TGC), individual phenolic profile, and antioxidant potential (DPPH, ABTS, FRAP) were examined experimentally in original and digested samples. Overall, SEM images of dried red cabbage showed more porous structures and minimal parenchyma deformation, enhancing bioactive compound bioaccessibility. Specifically, the bioaccessibility of TPC in IRD-dried samples was remarkably higher than that of FD- and LTVD-dried samples, although the latter two proved more TAC and TGC bioaccessible, respectively. Notably, hydroxycinnamic acids, such as ferulic and p-coumaric acids, markedly increased after digestion, especially in FD-dried samples. In vitro digestion revealed that CD-dried samples showed stronger DPPH and FRAP radical scavenging, whereas FD-dried samples had significantly higher ABTS scavenging activity. These findings suggest that LTVD and FD are the most suitable drying methods for red cabbage to enhance relevant bioactive compounds and, to some extent, antioxidant activity after digestion. Full article

This study aimed to investigate the impact of ultrasonic pretreatment vacuum drying (UAVD) and temperature on drying kinetics and qualitative attributes of blood oranges in comparison to several drying methods: hot air drying (HAD), vacuum drying (VD), and freeze drying (FD). The drying kinetics and modeling, total phenolic content (TPC), antioxidant capability (assessed using DPPH and ABTS tests), individual phenolic profiles, vitamin C concentration, and color factors were meticulously examined. Drying times were recorded as 22.5 h, 12.5 h, and 9 h for HAD; 11.5 h, 9.5 h, and 8.5 h for VD; and 10 h, 8.5 h, and 7.5 h for UAVD at 50, 60, and 70 °C, respectively. The HAD, VD, and UAVD procedures were conducted at 50, 60, and 70 °C, resulting in reduced drying periods with increasing temperature. The integration of ultrasound markedly lowered drying durations. Eleven thin-layer drying models were utilized to recreate the drying process precisely. The D_eff values of the HAD, VD, and UAVD dried samples varied from 9.08 × 10⁻⁶ to 2.82 × 10⁻⁵ m²/s, from 2.60 × 10⁻⁵ to 2.96 × 10⁻⁵ m²/s, and from 2.20 × 10⁻⁵ to 2.99 × 10⁻⁵, respectively. Among the desiccated blood orange slices, the greatest total phenolic content (TPC) was observed in freeze-dried samples (131.27 mg GAE/100 g), followed by those dried using ultrasonic-assisted vacuum drying (UAVD) at 50 °C (128.77 mg GAE/g DM). Dried blood orange slices had a vitamin C content of 29.79 to 49.01 mg/100. The drying process substantially impacted the color parameters L*, a*, and b*. These findings highlight the efficacy of ultrasound-assisted drying in decreasing drying duration while improving the retention of bioactive components in blood orange slices. Full article

In general, the acceptance of edible insects by consumers is low. Therefore, the aim of this research was to develop protein supplements from desiccated crickets. The objectives of this research were to study the effects of four different drying methods on the chemical properties of crickets and the effects of cricket powder fortification in vegetable chips on the chemical and physical qualities and consumer acceptance. Through an analysis of the chemical composition of cricket powder dried using hot air, vacuum, microwave, and freeze-drying methods, it was found that freeze-drying resulted in the highest protein content in the cricket powder, followed by vacuum drying, hot air drying, and microwave drying. However, the antioxidant activity, which was analyzed using DPPH, showed no significant differences across the four drying methods (p > 0.05). The sensory testing of chips by 30 consumers revealed that the chips with a 10:10 ratio of vegetable powder to cricket powder received the highest satisfaction results in all of the test attributes, ranging from “like” to “like very much”. When studying the chemical composition, hardness, and color of the chips, it was found that increasing the amount of cricket powder resulted in a decrease in lightness and yellowness, while redness and hardness increased. The antioxidant activity and phenolic content of the chips increased with the addition of cricket powder, while the flavonoid and potassium contents decreased as vegetable powder was replaced with cricket powder. In the formula most preferred by consumers, the antioxidant activity, phenolic content, flavonoid content, and potassium content were 60.90%, 6.25 ± 0.46 mg GAE/mg sample, 11.16 ± 0.1 mg QE/mg sample, and 0.66 ± 0.01%, respectively. Full article

The use of vacuum impregnation with onion and beetroot juice can help with the challenge of modifying plant tissue and fits in with current trends in the development of plant-based snacks. This study aimed to determine the effect of vacuum impregnation (VI) as a pretreatment before drying on the volatile compounds, texture profile, color, dry matter, water activity, and density of cauliflower. The pretreatment was carried out at a pressure of 0.06 MPa, and the total process time was 21 min. Two types of impregnation solutions were used: onion juice and beetroot juice. The samples were dried by freeze-drying and vacuum. Numerous volatile compounds were identified: twenty-two for raw cauliflower, twenty-nine for cauliflower after VI with beetroot juice, and twenty-four for cauliflower after vacuum impregnation with onion juice. The following volatile compounds were present in the highest amounts: 1-heptene, 2-methyl-(>60%), 2-ethylcyclobutanol (>4%), nona-3,5-dien-2-one (>1.8%), and two unidentified compounds, unknown 1 (probably an isomer of nona-3,5-dien-2-one (>1.8%)) and unknown 2 (probably a fatty acid) (>9.8%). The pretreatment had a significant effect on water activity, density, texture profile and color. The freeze-drying method proved to be effective in obtaining lower values of water activity and density. In addition, dried products obtained by this method were characterized by a higher degree of color recovery after rehydration and textural properties similar to fresh raw material. The use of different impregnation solutions had a significant impact on the properties studied. The greatest color change occurred in cauliflower treated with beetroot juice. Full article

In this study, the compositional shifts in free and bound phenolic compounds of Morinda citrifolia L. (Noni) processed by different drying methods were investigated. Twenty-seven phenolic compounds, predominantly rutin and quinic acid, were discovered in fresh Noni fruit. Vacuum freeze-drying retained the highest free phenolic content, with rutin (1809.83 mg/kg DW) and quinic acid (198.72 mg/kg DW) as the primary constituents, while bound phenolics were dominated by benzoic acid (35.56 mg/kg DW). Hot-air drying reduced the free phenolics by 51.59% (80% methanol) and the bound phenolics (base hydrolysis) by 35.55%, with a significant degradation of rutin and quinic acid. Microwave drying similarly decreased the free phenolics, though the caffeic acid increased to 46.45 mg/kg DW due to the thermal stability. Bound phenolics showed the highest content (alkaline hydrolysis) in fresh fruits, primarily benzoic acid (220.67 mg/kg DW) and rutin (77.02 mg/kg DW), surpassing the acid/enzyme methods. While vacuum freeze-drying effectively preserved the free phenolics, thermal methods (hot-air/microwave drying) promoted the release of quercetin (free phenols) and 3,4-dihydroxybenzoic acid (bound phenols). The findings of this study elucidate the species-specific compositional dynamics of phenolic compounds under different drying regimes, while providing quantitative guidelines for advancing the understanding of the underlying health-promoting phytochemical profiles of Noni. Full article

In this study, figs were dried by hot air drying (HD), vacuum freeze-drying (FD), vacuum drying (VD) and far-infrared drying (FID). Four fig polysaccharides (FPs) were extracted from different dried figs, and the corresponding names were FPH, FPF, FPV and FPFI. The effects of different drying methods on the structural properties, rheological properties and biological activities of FPs were compared. The result shows that the extraction rate of polysaccharides after FD (2.49%) treatment was 58.60%, 50% and 28.35% higher than that of HD (1.57%), VD (1.66%) and FID (1.94%), respectively. Drying methods result in varying molar ratios of monosaccharides. FPFI has more stable gel properties. HD, VD and FID caused damage to the surface structure of the polysaccharides. FPF exhibited the highest uronic acid content (25.56%), along with relatively low apparent viscosity and molecular weight (1.45 × 10⁵ Da), which contributed to its superior antioxidant and lipid-lowering activities. Therefore, FD is a drying method to obtain fig polysaccharide with high antioxidant and hypolipidemic activity. The results provided a scientific basis for the drying process of fig polysaccharide and a reference for the development of potential hypolipidemic products of fig polysaccharide. Full article

α-Tocopherol (α-T) predominates in photosynthetic tissues, while tocotrienols (T3s) are reported very rarely. The genus Hypericum stands out as one of the few exceptions. Given the potential health benefits associated with tocotrienols, sourcing them from natural origins is of interest. The proper selection of plant material and the drying conditions are crucial steps in this process. Therefore, in the present study, we investigated the effects of four different drying techniques (freeze-drying, microwave–vacuum-, infrared oven and air-drying) on the tocochromanol content in leaves of three Hypericum species: H. androsaemum, H. pseudohenryi, and H. hookerianum and one hybrid H. × inodorum. The total tocochromanol content in the freeze-dried leaves harvested in September was 68.1–150.6 mg/100 g dry weight. α-T constituted 66.7–85.9% (w/w), while tocotrienols constituted 13–32% (w/w). H. pseudohenryi was characterized by the lowest tocotrienol content, while H. androsaemum and H. hookerianum had the highest, with δ-T3 and γ-T3, respectively, being predominant. Tocotrienols were more stable during drying than α-T. The greatest decrease in α-T content was observed during air-drying in the presence of sunlight, with a 27% difference compared to the absence of sunlight. The species and harvest time are factors that more strongly affect the tocotrienol content in the Hypericum leaves than the selected drying method. Full article