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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 a...
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... these parameters are important for a proper evaluation of many other properties of freeze-dried foods, it has been noticed that many investigators do not always measure and control the values of the water content and water activity after freeze-drying. Table 1 shows the values of water activity and water content obtained for freeze-dried materials in different operational conditions. The water content for most of the freeze-dried products varied from 0.01 to 0.1 g/g d.m., and water activity ranged from 0.08 to 0.330. ...Similar publications
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Citations
... Tropical fruits, particularly watermelon, orange, and mango, represent significant economic value in both fresh and processed forms due to their distinctive organoleptic properties and rich nutritional profiles, including vitamins, minerals, antioxidants, and bioactive compounds (Vicente et al., 2022). The freezedrying process involves the removal of water through sublimation under vacuum conditions, resulting in a highly porous structure that preserves the original shape and volume of the product (Nowak & Jakubczyk, 2020). While this process yields superior-quality products, the resulting porous structure makes freeze-dried materials particularly susceptible to moisture absorption, which can lead to various degradation phenomena including loss of crispness, structural collapse, enzymatic reactions, and microbial growth (Ngamwonglumlert & Devahastin, 2018). ...
The moisture adsorption characteristics of freeze-dried watermelon, orange, and mango composite fruit purees were determined using the standard gravimetric method at 20, 25, 30, 40 and 50°C respectively over a water activity range of 0.11-0.95 and the data analyzed using the BET, GAB and Oswin sorption models. The data obtained and moisture permeability characteristics of commercial aluminium pouches, low density polyethylene (LDPE), Melinex 813, and Propafilm C flexible materials were used for shelf life prediction at various ambient storage temperatures. Sorption data exhibited type III isotherms, typical of foods rich in soluble components. The GAB model provided the best fit for the experimental data compared to the other tested models. BET monolayer moisture contents (4.72 – 8.80 g H2O/100g solids) decreased with increasing temperature indicating reduced water binding sites at higher temperatures. Net isosteric heats (0.00012 to 0.0052 kJ/mol) decreased while the entropy of adsorption (-0.1343 to -0.0312 kJ/mol.oC) increased with moisture content. The predicted shelf life was highest for Aluminum pouch followed by, Propafilm C, LDPE and Melinex 813 in that order. This study provides valuable insights for optimizing storage conditions and packaging selection for freeze-dried composite fruit products, with practical implications for commercial applications in the food industry.
... Polyvalent lyophilization (freeze-drying) approaches are widely used in the preservation of heat-sensitive and delicate biological substances/tissues, notably in the food industry and in medical/pharmaceutical applications [16][17][18][19][20][21][22][23][24][25][26]. Specifically, slow and controlled moisture removal notably enhances sample stability while maintaining nutritional integrity and the critical properties of enzymes and antioxidants [16,23,25]. ...
... Polyvalent lyophilization (freeze-drying) approaches are widely used in the preservation of heat-sensitive and delicate biological substances/tissues, notably in the food industry and in medical/pharmaceutical applications [16][17][18][19][20][21][22][23][24][25][26]. Specifically, slow and controlled moisture removal notably enhances sample stability while maintaining nutritional integrity and the critical properties of enzymes and antioxidants [16,23,25]. Thus, obtaining an extended product shelf-life through lyophilization is achieved by reducing water activity, inhibiting microbial growth, oxidation processes, and enzymatic degradation [24,[27][28][29]. ...
... Thus, obtaining an extended product shelf-life through lyophilization is achieved by reducing water activity, inhibiting microbial growth, oxidation processes, and enzymatic degradation [24,[27][28][29]. By preserving cellular and protein structures and by preventing the degradation of sensitive compounds during dehydration, the stability and bioavailability of lyophilized tissuebased extracts are optimally conserved [16,23,27]. Furthermore, lyophilized materials and foodstuffs possess preserved nutritional values, are lightweight and condensed, retain flavors, and are easily rehydrated [16,[23][24][25][26]. ...
Lyophilized organ extracts from livestock such as beef or elk are widely commercially proposed as animal-sourced nutraceuticals. Such preparations contain blends of vitamins and nutrients that may be employed for general or specific dietary supplementation. The first objective of this study was to develop an optimized and function-oriented manufacturing process for stabilized organ-specific extracts of American buffalo (Bison bison). The second objective of the study was to perform functional benchmarking of the obtained stabilized extracts by focusing on antioxidant attributes, which are key properties of nutraceuticals. Methodologically, a two-step lyophilization process, hard-shell capsule formulation, and process quality control elements were adapted from pharmaceutical technology practices. Stabilized extracts (300 mg capsules) were derived from the spleen, heart, liver, kidneys, lungs, and thymus of grass-fed and grass-finished American bison (born and raised in a tempered climate in Geneva, Switzerland). Functional benchmarking of the obtained extracts was performed using orthogonal methods of antioxidant activity determination (TEAC, FRAP, and H2O2 challenge assays). Firstly, the developed biomass transformation process enabled the considered organs to be effectively stabilized while reaching the desired quality attributes. Secondly, functional characterization of the formulated extracts revealed significant and organ-specific antioxidant attributes, wherein liver-derived materials were found to be the most potent. Thirdly, key quality and functional parameters (residual moisture levels and TEAC) were found to be stable over 12 months of storage following extract preparation. Overall, the present study provides an evidence-based technical/functional rationale for the preparation and control of American bison organ-specific lyophilized extracts to be included in nutraceutical preparations.
... However, VFD faces several challenges, such as stringent equipment standards, high initial capital investment, and relatively low yield and operational efficiency. 7 In addition, the complexity of the process and the maintenance requirements necessitate skilled operators. Precise control of temperature and pressure during material preparation is crucial to preserve material properties. ...
Vacuum freeze-drying (VFD) technology has gained extensive application across various sectors, particularly in environmental applications, where it is primarily utilized for the fabrication of environmental functional materials and the conservation of environmental organisms. This technology is applicable to soil enhancement, the remediation of aquatic pollutants, energy storage in thermoelectric materials, and the preservation of bacterial cultures. This review synthesizes the most recent advancements in VFD technology within the environmental domain, elaborating on its technical fundamentals, operational procedures, practical applications, and distinctive benefits. Furthermore, the article explores the prospective development trajectory and potential challenges for this technology in the environmental sector, offering scientific guidance for its continued application and insights into its innovative progression.
... Consistent with our findings, an evaluation of the effects of different drying methods (sun drying, hot air drying, microwave drying, vacuum drying, and freeze drying) on the bioactive compounds, antioxidant activity, and antidiabetic effects of wild guava leaves revealed that freeze-dried leaves had the highest levels of total phenolic content, gallic acid, total flavonoids, and antioxidant capacity compared with the other methods. In contrast, sun-dried leaves exhibited the lowest values for these parameters [55]. Freeze-drying, known as lyophilization, involves freezing water into ice under low pressure and then removing it through sublimation. ...
Background
Drying is a critical post-harvest process for medicinal plants, which are typically high in moisture and microorganisms. To prevent spoilage and quality loss, it is essential to dry these plants promptly. The drying method significantly impacts the levels of secondary metabolites and the organoleptic characteristics of medicinal plants. This study aimed to investigate the effects of various drying methods on the total phenolics, flavonoids, anthocyanins, antioxidant activity, and phenolic acids in caper (Capparis spinosa L.) fruits. The experiment was performed using a completely randomized design with three replications and included 11 treatments: shade drying, sun drying, oven drying (at 50 °C, 60 °C, and 70 °C), microwave drying (at 300 W, 600 W, and 900 W), freeze-drying, salt-drying, and a fresh plant sample as a control.
Results
Among the drying methods tested, microwave drying consistently produced the highest levels of flavonoids, anthocyanins, and antioxidant activity, regardless of wattage. Specifically, the highest total phenol content was observed in samples dried at 900 W microwave, 600 W microwave, and 70 °C in the oven (5.3, 5.37, and 5.31 mg GAE/g DW, respectively). Drying at 600 W microwave yielded the highest levels of caffeic, cinnamic, ferulic, vanillic, and protocatechuic acids (13.03, 3.85, 4.28, 9.73, and 5.6 µg/g, respectively) while drying at 900 W microwave also resulted in elevated levels of caffeic, ferulic, protocatechuic, and p-coumaric acids. The 70 °C oven drying method also showed high levels of caffeic, cinnamic, ferulic, vanillic, and protocatechuic acids. Freeze-drying achieved the highest levels of rosmarinic, gallic, and m-coumaric acids (320.17, 175.3, and 12.99 µg/g, respectively), while shade drying produced high levels of p-hydroxybenzoic, cinnamic, ferulic, m-coumaric, protocatechuic, and p-coumaric acids.
Conclusions
Overall, microwave drying (especially at 600 W), oven drying at 70 °C, and freeze-drying emerged as effective alternatives to traditional drying methods. These methods not only preserved the color, texture, and taste of the fruits but also enhanced their bioactive compound levels.
... As the FD operation is carried out under low temperature and vacuum conditions, it prevents browning and maximally retains the intrinsic nutritional components of the material. 7 Compared with other singular drying methods, the product after FD exhibits minimal shrinkage, fully preserving the appearance of the food. Structurally, it presents a porous formation, facilitating rapid rehydration. ...
BACKGROUND
Fresh Cistanche deserticola, a valuable medicinal and dietary ingredient with exceptional functional properties, exhibits a high moisture content and is susceptible to deterioration due to its high moisture content. Therefore, it is imperative to identify an appropriate dehydration method. This study primarily focuses on enhancing the efficiency and quality of dried C. deserticola, through a hybrid drying process that combines freeze‐drying (FD) and infrared drying (IRD). The samples were first dehydrated by FD and then transferred to IRD until the end of drying, with different moisture transition points (based on FD durations of 5.5, 6.0, 6.5, and 7.0 h, and the corresponding groups are marked as FD5.5h‐IR, FD6.0h‐IR, FD6.5h‐IR, and FD7.0h‐IR).
RESULTS
The FD6.5h‐IR method proved to be 32.08% more energy efficient than the sole FD method. The microscopic examination revealed that the surfaces of samples treated using the FD6.5h‐IR and FD7h‐IR techniques were smoother and clearer with smaller and more uniform pores, similar to the microstructure of the solely FD sample. Furthermore, the FD6.5h‐IR treatment has been demonstrated to be highly effective in maintaining the retention of active ingredients in products.
CONCLUSION
Given the disadvantage of FD7h‐IR treatment in terms of energy consumption, FD6.5h was identified as the best moisture transition point. This investigation offers a theoretical basis for enhancing quality control and refining the process during the FD–IRD processing of newly harvested C. deserticola slices. © 2025 Society of Chemical Industry.
... Under conditions of low temperature and high vacuum, the removal of ice crystals via sublimation leads to cell lysis. The FD process, characterized by moderate temperature exposure and an anaerobic environment, effectively preserves thermolabile compounds, making it a mild and effective dehydration method that maintains the integrity of sensitive bioactive constituents [46]. ...
The abundant yet underutilized olive leaves, a renewable by-product of olive cultivation, offer untapped potential for producing high-value bioactive compounds, notably oleacein. Existing extraction methods are often inefficient, yielding low quantities of oleacein due to enzymatic degradation of its precursor, oleuropein, during conventional processing and storage. This study aimed to overcome these limitations by exploring a novel methodology based on freeze-drying, to facilitate the in situ enzymatic biotransformation of oleuropein into oleacein directly within the plant matrix. Olive leaves were subjected to three drying methods—ambient air drying, microwave drying, and freeze-drying—and their phenolic profiles were analyzed. The findings demonstrated that FD uniquely promotes the selective activation of β-glucosidase and esterase enzymes while simultaneously inhibiting oxidative enzymes, such as polyphenol oxidase and peroxidase, resulting in significantly enriched OLEA content. This process eliminates the need for extensive post-extraction transformations, providing a cost-effective, scalable, and sustainable approach to OLEA production. The proposed methodology aligns with circular economy principles and holds substantial potential for applications in pharmaceuticals, nutraceuticals, and functional food industries.
... Quá trình đông khô bao gồm đóng băng vật liệu, giảm áp suất và gia nhiệt để vật liệu thăng hoa. Quy trình đông khô đã được sử dụng rộng rãi trong ngành dược phẩm và công nghệ sinh học để bảo quản vắc-xin, dược phẩm, sản phẩm máu và mô [11]. Tuy nhiên, việc áp dụng và tối ưu hóa quy trình đông khô, đặc biệt cho sản phẩm PRF còn hạn chế. ...
Sợi huyết giàu tiểu cầu (PRF) là sản phẩm tự thân chiết xuất từ máu toàn phần đã được sử dụng như vật liệu tái tạo tự thân. Việc sử dụng PRF còn hạn chế do thời gian phân huỷ nhanh và tính ổn định cơ học thấp. Mục tiêu của nghiên cứu này là chế tạo sợi huyết giàu tiểu cầu dạng đông khô và xác định tính chất hóa học của chúng sau khi chế tạo. Một tình nguyện viên, khoẻ mạnh, không ghi nhận bệnh lý toàn thân hay lây nhiễm được lấy máu toàn phần A-PRF và S-PRF. 10mL máu toàn phần được quay ly tâm lần lượt với lực quay 250g trong 14 phút và 200g trong 14 phút. Lớp PRF được thu về và được đông khô bằng cách lưu trữ ở nhiệt độ -80oC qua đêm và sấy khô bằng máy đông khô Labconco ở -51oC trong 12 giờ. Các mẫu PRF đông khô (Ly-APRF và Ly-SPRF) được kiểm tra lần lượt bằng kính hiển vi điện tử quét và phương pháp phổ hồng ngoại biến đổi Fourier. Hình ảnh SEM thể hiện cấu trúc sợi huyết còn lưu giữ sau quá trìnhh đông khô. FTIR cho thấy các nhóm amide I, II, III tương đồng giữa Ly-APRF và Ly-SPRF. Việc đông khô PRF là phương pháp tiềm năng để cải thiện tính chất và lưu trữ vật liệu tự thân này.
... Conventional methods for drying fruits and vegetables include vacuum drying, sun drying, freeze-drying, fluidised bed drying, tray drying, and oven drying (Doymaz, 2004;Kaleta et al., 2013;Antal, 2015a;Li et al., 2020). Freeze-drying (FD), which involves the removal of water through sublimation (Nowak and Jakubczyk, 2020), is highly favoured by food processors and consumers due to the excellent physical and chemical qualities of the resulting dried product. These qualities include faster rehydration, minimal shrinkage, high colour retention, low bulk density, and high nutrient and bioactive phytochemical content (Que et al., 2008;Antal, 2015a;Valadez-Carmona et al., 2017;Zhou et al., 2021). ...
Introduction: An effective and efficient drying method for preserving fresh carrots is essential in food processing. Combined drying represents a novel approach that addresses the shortcomings of conventional methods by balancing energy consumption, cost, and product quality.
Methods: This study evaluated the impact of combining oven drying (OD) with freeze-drying (FD) on drying behavior, energy requirements, costs, enzyme activity, and the physicochemical and sensory properties of dried carrots. Drying conditions included 36 hours of FD, OD, and combinations of OD and FD at 1 h of OD + 21 h of FD (OD1-FD21), 2 h of OD + 18 h of FD (OD2-FD18), 3 h of OD + 15 h of FD (OD3-FD15), and 9 h of OD.
Results and discussion: Compared to FD alone, the OD-FD combination reduced drying time by 39–50% and decreased energy consumption and costs by 40–56%. FD and OD-FD reduced polyphenol oxidase activity by 71–85% and peroxidase activity by 29–52% compared to OD alone. FD carrot slices retained significantly higher levels of β-carotene (11.67–25.96 mg/100 g DM), lycopene (9.91–21.85 mg/100 g DM), total phenolic content (7.12–10.24 mg GAE/100 g DM), and DPPH radical scavenging activity (16.44–19.38 mM AAE/100 g DM) than OD and OD-FD slices. OD-FD slices exhibited the highest levels of volatile compounds, including aldehydes, terpenes, esters, alcohols, ketones, and acids, indicating superior flavor preservation.
Conclusion: The OD2-FD18 combination emerged as the optimal method, significantly reducing energy consumption and costs while maintaining better β-carotene, total phenolic content, DPPH radical scavenging activity, and volatile compound profiles. This study highlights the potential of combined drying methods to enhance drying efficiency and product quality.
... However, the dehydration percentages were higher in fillets with smaller masses (2,500 kg) freezedried for 30 and 36 hours. Different factors can influence the results of food freeze-drying, such as heating temperature, use of pre-treatments, equipment load capacity, degree of vacuum and freezing, which can interfere with the quality of the product, whether in appearance, moisture content or nutritional composition (Nowak and Jakubczyk, 2020). ...
... According to the researchers, these effects were attributed to the processing time, which directly affected the skin properties by removing water (bound, retained, and free) during drying. In freeze-dried products, porosity is an essential element for predicting quality since the distribution and size of pores especially influence crispness (Nowak and Jakubczyk, 2020 The appearance of the fillets changed during the process, especially with increasing L* (luminosity) and with the samples darkening. Fish muscle discoloration can be affected by different factors: drying, postmortem storage, microbial and biochemical changes, salting and brining, modified atmosphere packaging using CO2 and thermal processing (Singh et al., 2022). ...
... crystals directly affect the properties and structures(Nowak and Jakubczyk, 2020;Tan et al., 2021). In addition to the morphological characteristics of the products, in freeze-drying, the shape and size of the ice can also interfere with the sublimation rates (Petzold andAguilera, 2009). ...
This study aims to investigate the effects of freeze-drying on the structure of freeze-dried Oreochromis niloticus tilápia fish at different processing times. Foram analyzed water activity (Aw), texture, core and Varredura Electron Microscopy (MEV). The results demonstrate alterations in the theory of mass and structure of two fibers over a long period of time, with the formation of fissures and detachment of muscle fibers. The effects of the process are greater than we file them with less mass theory (2.5 kg) freeze-dried for 36 hours. The use of freeze-drying for dehydration of tilápia fish has been shown to be effective, providing the removal of water theory from two tissues. Meanwhile, its use causes alterations in the physical-chemical and structural properties of the food. For this reason, even sensory analysis is necessary, aiming to better understand the effects of the process on the other characteristics and oilability of the product, such as the flavor of the filé.
... In recent years, there has been a growing interest in the freeze-drying of traditional foods like rendang to extend their shelf life while maintaining their sensory attributes. Freeze-drying, or lyophilization, is a dehydration process typically used to preserve perishable materials, where water is removed by sublimation under low pressure and temperature conditions [7]. This method is particularly suitable for rendang, which, after its prolonged cooking, already has a relatively low moisture content, making it an excellent candidate for freezedrying. ...
Beef rendang, a traditional prolonged cooking dish from Malaysia and Indonesia, reflects the Quranic principles of preservation and nourishment, emphasizing the consumption of pure, lawful, and wholesome food (Surah Al-Baqarah 2:172). Its preparation, combining meat protein, coconut milk, and spices, symbolizes the bounty and sustenance provided by Allah. While the dish is known for its rich flavors and extended shelf life, prolonged cooking can lead to moisture loss and alterations in water activity (aw), both crucial for maintaining food safety and quality. This study examines the impact of varying coconut milk concentrations on the moisture content and water activity of freeze-dried beef rendang. Samples were prepared with coconut milk concentrations of 0%, 25%, 50%, 75%, 100%, and 125%, cooked for durations ranging from 0 to 4 hours at 120°C, and subjected to freeze-drying. Moisture content analysis revealed reductions ranging from 2% to 10%, demonstrating effective moisture removal across samples. However, water activity analysis indicated significant differences in the availability of free water, likely influenced by coconut milk's fat and water-binding properties. These findings highlight how coconut milk affects initial moisture levels, while freeze-drying stabilizes the final moisture content. The nuanced understanding of water activity reflects the balance in preservation processes, resonating with the Quranic call for equilibrium and purity in food preparation (Surah Al-Baqarah 2:168). This study emphasizes optimizing cooking methods to preserve the quality and safety of beef rendang while aligning with Islamic values of sustainability and stewardship.