Literature search strategy

This study was designed as a narrative review focusing on colostrum drying technologies and the use of fluidized bed drying as a post-drying approach for improving powder functionality. Relevant literature published in English between 2000 and 2025 was retrieved from scientific databases including Scopus, Web of Science and Google Scholar. Keywords such as ‘colostrum’, ‘spray drying’, ‘freeze drying’, ‘fluidized bed drying’, ‘agglomeration’ and ‘functional food’ were used during the literature search process. Studies related to the preservation, drying, powder properties and functional applications of colostrum were primarily considered for inclusion.

Colostrum

Colostrum is the mammary gland secretion produced immediately after birth, generally defined as milk secreted within the first 72 h postpartum, although some studies extend this period up to 7 days (Abd El-fattah et al., Reference Abd El-fattah, Abd Rabo, El-dieb and El-kashef2012; McGrath et al., Reference McGrath, Fox, McSweeney and Kelly2016). It provides the first supply of vital nutrients, including high concentrations of protein, fat, carbohydrate, water, and fat-soluble vitamins and minerals, as well as antibodies and growth factors necessary for nutrition, protection, development, immunological defence and a healthy life of the newborn (Abd El-fattah et al., Reference Abd El-fattah, Abd Rabo, El-dieb and El-kashef2012). Both the newborn calf’s immunoglobulin concentration in blood and intestinal permeability decrease rapidly in the first 24 h after birth, and are therefore dependent on their mothers’ colostrum for immunity (McGrath et al., Reference McGrath, Fox, McSweeney and Kelly2016).

Compared to mature milk, colostrum contains less lactose and more fat, protein, peptides, non-protein nitrogen, ash, vitamins and minerals, hormones, growth factors, cytokines and nucleotides (McGrath et al., Reference McGrath, Fox, McSweeney and Kelly2016). The important components of colostrum fall into three main categories: nutritional factors, immune factors and growth factors. Colostrum is particularly rich in immunoglobulins, lactoferrin, and growth and antimicrobial factors, which promote tissue growth, digestive system maturation and immune function in newborn animals and humans. Bovine colostrum contains lactose, oligosaccharides, glucolipids, glycoproteins and nucleotide sugars as carbohydrates. Lactose is the predominant carbohydrate in colostrum, at approximately 2.5%. The lactose content in colostrum is lower than that found in bovine and human milk, but it contains 1 g/l of dietary oligosaccharides, which is approximately twice the amount in milk. Since dietary oligosaccharides cannot be digested in the intestine, they act as prebiotics. Bovine colostrum contains approximately 7% fat and is mainly composed of milk fat globules, approximately twice that of the fat content in milk. Most vitamins found in colostrum, especially vitamins B2, B12, E and D, and many essential minerals, including calcium, copper, iron, zinc, magnesium, manganese and phosphorus, are in higher amounts than in milk (Abdelsattar et al., Reference Abdelsattar, Rashwan, Younes, Abdel-hamid, Romeih, Mehanni, Vargas-Bello-Pérez, Chen and Zhang2022; Borad and Singh, Reference Borad and Singh2018).

After calving, the composition of colostrum changes significantly. Therefore, feeding the calf with colostrum when it is born (within 0.5–1 h) is very important. The highest quality colostrum containing the maximum concentration of bioactive compounds is obtained by milking the animal within 6 h after birth (Puppel et al., Reference Puppel, Gołębiewski, Grodkowski, Slósarz, Kunowska-Slósarz, Solarczyk, Łukasiewicz, Balcerak and Przysucha2019).

Colostrum preservation methods

In food processing, the aim is to ensure food safety, enhance quality and extend its shelf life without changing the nutritional content of the food. The applied process aims to reduce the microorganisms that cause spoilage, eliminate pathogenic microorganisms, inactivate natural enzymes, slow down spoilage and protect natural food elements.

The processing and preservation of colostrum is essential in creating a colostrum bank for newborn calves whose mothers cannot feed them immediately after birth (Abdelsattar et al., Reference Abdelsattar, Rashwan, Younes, Abdel-hamid, Romeih, Mehanni, Vargas-Bello-Pérez, Chen and Zhang2022). In addition, excess colostrum obtained after birth can provide passive immunity to newborn calves when the amount of colostrum is insufficient or lacks quality. However, the shelf life of liquid colostrum is quite limited (Salar et al., Reference Salar, Jafarian, Mortazavi and Nasiraie2021). It is reported that giving colostrum at a rate of 7–10% of the body weight of calves is sufficient for developing passive immunity (Borad and Singh, Reference Borad and Singh2018). Therefore, colostrum may be in excess on large farms. If the farm’s colostrum processing and preservation technologies are lacking, the nutraceutical properties of colostrum cannot be utilized.

Furthermore, since colostrum has recently found a place of use in human health and nutrition, it is important to produce colostrum in a form suitable for the food matrix in functional food production (Borad and Singh, Reference Borad and Singh2018). Colostrum should be produced in a suitable powder form, so that it can be used not only in human nutrition but also in the nutrition of different animals other than the animal from which it is secreted (Gorbannejhad Parapary et al., Reference Gorbannejhad Parapary, Nobakht and Mehmannavaz2021). All these reasons make it important to develop appropriate processing methods for colostrum milk.

To extend the shelf life of bovine colostrum without reducing its hygienic quality and immunoglobulin level, some preservation methods such as cooling, freezing, chemical preservation, freeze drying, spray drying and pasteurization should be applied. The most common preservation methods used for colostrum are pasteurization and drying (Abd El-fattah et al., Reference Abd El-fattah, Abd Rabo, El-dieb and El-kashef2014; Abdelsattar et al., Reference Abdelsattar, Rashwan, Younes, Abdel-hamid, Romeih, Mehanni, Vargas-Bello-Pérez, Chen and Zhang2022; Sotudeh et al., Reference Sotudeh, Rabbani Khorasgani, Etemadifar and Zarkesh-esfahani2018). Colostrum preservation methods, including heat treatments, chemical applications and emerging technologies, and the effect of each treatment are given in Table 1.

Table 1.

Colostrum preservation methods including heat treatments, chemical applications and emerging technologies

Table 1 Long description

Two columns list treatment and effects on colostrum components. Cooling and freezing entries include cooling to 4 degrees C with a small gradual IgG decrease; storage at minus 20 degrees C for 1 year with no change in IgA or IgM but decreased IgG after 32 weeks; storage at 4.0 degrees C up to 240 hours with no change in chemical composition and microbiological properties; storage at 4 degrees C for 3 months with reduced IgG; storage at 4 degrees C up to 48 hours and at minus 20 degrees C or minus 80 degrees C for at least 6 months without losing immunological properties; and minus 20 degrees C for 3 months with about a 10.42 percent IgG decrease. Heat treatment entries include pasteurization at 57 degrees C for 10 minutes with IgG reduced by 37.84 percent and CFU decreased; pasteurisation at 60 degrees C for 60 minutes with no effect on IgG activity and viscosity; pasteurisation at 63 degrees C for 30 minutes or 72 degrees C for 15 seconds with decreased IgG and increased viscosity; and heating above 65 degrees C with a sharp IgG decrease. Chemical applications include potassium sorbat with citric acid, where potassium sorbate has lower coliform and aerobic microorganism counts, and citric acid with a significant decrease in Ig concentration. Combined methods include glycerol before heat treatment at 56 degrees C for 1 hour with improved bacterial reduction without affecting immune properties in goat colostrum, propylene glycol before the same heat treatment with reduced various immune variables in goat colostrum, and pasteurization at 60 degrees C for 60 minutes before storage at minus 20 degrees C reducing total plate counts and total coliform counts. Comparing methods includes heat at 56 degrees C for 60 minutes and 63 degrees C for 30 minutes versus high pressure homogenization at 400 and 500 MPa for 10 minutes at 20 degrees C, with almost similar bacterial reduction but significant IgG loss at 500 MPa, and heat for 20 seconds at 70 degrees C versus high pressure processing at 345 MPa for 4 minutes at 30 degrees C, with 5 log E. coli reduction in both and 25 percent Ig loss in high pressure. Emerging technologies include microfiltration at 0.22 micrometers with 9.0 percent IgG loss, microfiltration at 1.4 micrometers with a 4 log decrease in live bacteria and a 10 to 30 percent IgG decrease, gamma irradiation around 14 kGy with more sterile but lower Ig and increased bioactive protein denaturation, ultraviolet light with decreased bacterial count and 50 percent Ig decrease, high pressure homogenization with slight IgG decreases at 200, 300, and 500 bar in 10 minutes and the highest IgG loss at 500 MPa, and high hydrostatic pressure where 300 MPa or above inhibits several bacterial counts and 400 MPa or above causes gelling and immunoglobulin denaturation.

Heat treatment is a widely used process in the food and dairy industries. Long-term storage of high-quality colostrum without microbial contamination is one of the main challenges in producing colostrum-based products for human consumption. Although colostrum may be contaminated by various pathogenic microorganisms, particular concern has been raised regarding Mycobacterium avium ssp. paratuberculosis, Mycoplasma spp., Escherichia coli and Salmonella spp. Pathogenic bacteria can be transmitted to newborns via colostrum. These pathogens are usually transferred to colostrum during milking and develop during storage, posing a potential risk to the final product. Therefore, heat treatments such as pasteurization and sterilization are required to effectively destroy pathogens and obtain high-quality colostrum (Abd El-fattah et al., Reference Abd El-fattah, Abd Rabo, El-dieb and El-kashef2014; Kaplan et al., Reference Kaplan, Arslan, Duman, Karyelioğlu, Baydemir, Günar, Alkan, Bayraktar, Tosun and Ertürk2022). Pasteurization at 60°C for 60 min before storage at −20°C was reported to reduce total plate counts and total coliform counts by 1–2 log10, which reduced morbidity and mortality in calves from 15% to 5.2% and from 6.5% to 2.8%, respectively (Armengol and Fraile, Reference Armengol and Fraile2016). It has been reported that temperature treatments above 65°C for goat colostrum cause a sharp decrease in the amount of IgG (Shao et al., Reference Shao, Cheng, Zhang, Wang and Jiang2021).

Drying methods of colostrum

Drying of foods is one of the oldest and most common food preservation methods. It is an important process that consumes large amounts of energy in the food industry and is very effective in determining the quality of the final product. Dried foods are stable under ambient conditions, have a long shelf life, are easy to use and are easily incorporated into food formulations. At the same time, the final product’s weight and volume are reduced by drying processes, facilitating packaging, transportation, and storage and reducing costs. Certain drying technologies can reduce water activity (aw) to below 0.2, resulting in improved microbial and chemical stability (Ahmed et al., Reference Ahmed, Singh, Chauhan, Anjum and Kour2013; Borad and Singh, Reference Borad and Singh2018). The findings summarizing the effects of drying methods on the biofunctional properties of colostrum are shown in Table 2.

Table 2.

The effect of drying methods on the biofunctional properties of colostrum

Table 2 Long description

Two columns list drying methods and reported effects on colostrum components. Freeze drying entries report a linear increase in colour difference with a slight IgG decrease, colostrum powder with significant amino acids, minerals and IgG, dromedary milk powder with nutritional and superior FRAP antioxidant properties, no changes in secondary structures with higher recovered IgG than IgM and IgA, a decrease in DPPH radical scavenging activity and IgG content, and a small IgG decrease of 6.55 percent. Spray drying entries report 88 percent of Ig preserved in colostrum protein preparations, and a significant IgG decrease during the first 30 days with an increase in HMF. A section labeled, Comparing methods includes spray and freeze drying studies reporting a statistically significant difference in lactoferrin concentration but not IgG protein, immune protein preservation described as better in freeze drying and aroma and antioxidant properties described as better in spray drying, and high IgG concentration with good loose bulk density, fluidity, wettability and solubility properties in freeze dried colostrum. Additional comparisons report slight protein denaturation in both processes with no significant difference in radical scavenging activities, higher IgG concentration in freeze drying at 36.97 plus or minus 6.79 milligrams per millilitre than spray drying at 30.65 plus or minus 6.95 milligrams per millilitre, 30 percent more vitamin C loss in a frozen sample than freeze dried mare colostrum after 12 months storage, and high intestinal absorption in freeze dried colostrum compared with commercial powder.

Spray drying

Spray drying is a technique used to convert liquids into powders. It is widely used in the food, chemical, pharmaceutical and cosmetic industries (Eijkelboom et al., Reference Eijkelboom, Van boven, Siemons, Wilms, Boom, Kohlus and Schutyser2023). The spray-drying system has three main components: an atomiser, a drying chamber and a collector. In the spray-drying process, a solution or suspension of raw materials is sprayed into a hot environment with an atomizer. When the product comes into contact with a hot environment, its moisture evaporates quickly, the droplets turn into dry particles and the process lasts only a few seconds (Alhajj et al., Reference Alhajj, O'Reilly and Cathcart2021).

A study by Borad et al. (Reference Borad, Singh, Meena, Arora, Raju and Sabikhi2021) showed that inlet temperatures did not significantly affect Ig contents of colostrum powders dried with the spray-drying method at different temperatures (150°C, 165°C and 180°C). It was also stated that 88% of the Ig was preserved due to spray drying. In another study, cow and buffalo colostrum powder with 12% and 15% yields were produced using a spray dryer at an inlet temperature of 160°C (Sahana et al., Reference Sahana, Ramasamy, Pugazhenthi and Manikkavasagan2018). Fatima et al. (Reference Fatima, Sajid, Saima, Nadeem, Ahmad, Mehmood, Zubair Khalid, Ali Alharbi, Ansari and Kasongo2024) compared the properties of powdered colostrum samples dried by freezing and spray drying (inlet temperature: 125°C). According to the research, freeze-dried colostrum powder had higher levels of defence proteins (IgG and IgA), DPPH activity and higher sensory appearance scores. The spray-dried powder’s FRAP (ferric reducing antioxidant power), ABTS (2,2-azino-bis-3-ethylbenzothiazoline-6-sulphonic acid) and TPC (total phenolic content) values, flavour, and aroma sensory scores were determined to be higher than those in the freeze-dried powder. In the study by Borad et al. (Reference Borad, Singh, Meena and Raghu2020), diluted non-fat colostrum and colostrum whey samples subjected to ultrafiltration were dried in a spray dryer. The loss of IgG activity in the retentate colostrum whey powder was found to be significantly greater than the loss of IgG activity in the retentate non-fat colostrum powder. In the study by Yu et al. (Reference Yu, Zheng and Li2015), bovine colostrum powders produced using spray drying were stored for 90 days under different storage conditions, and the powders’ shelf life and storage stability were evaluated. As the storage period increased, the moisture and HMF content of the spray-dried colostrum powders gradually increased. The IgG content significantly decreased during the first 30 days, followed by a gradual decline throughout the remaining storage period. In a study conducted to determine the shelf life of powdered colostrum, the shelf life of spray-dried colostrum powder was determined to be 425.5 and 86.5 days in aluminium-laminated polyethylene (ALPE) and polyethylene terephthalate (PET) bags, respectively, under conditions of 25°C and 50% relative humidity (RH) (Yu et al., Reference Yu, Zheng and Li2015).

Although spray drying is relatively cheaper and faster, the changes in morphology and particle size, loss of aroma and thermal degradation observed in the drying of dairy products are the main disadvantages of this method. Especially, as colostrum proteins are sensitive to heat, the production of colostrum powder by spray drying has remained limited. Given the heat-sensitive nature of colostrum, it is conceivable that traditional pasteurization of colostrum before spray drying may be omitted. However, the dried powder product may contain pathogens and spoilage microorganisms. Therefore, it is necessary to optimize spray-drying conditions and evaluate thermal preservation effectiveness to ensure microbial safety (Borad and Singh, Reference Borad and Singh2018; Borad et al., Reference Borad, Singh, Meena, Arora, Raju and Sabikhi2021).

Freeze drying

Freeze drying, also known as lyophilization, is a dehydration method. The method involves freezing the product, reducing the pressure and removing the frozen water in the product by sublimation (Castro-albarrán et al., Reference Castro-Albarrán, Aguilar-Uscanga, Calon, St-amour, Solís-Pacheco, Saucier and Ratti2016; Jia et al., Reference Jia, Jiang, He and Wang2021).

Compared to raw colostrum, the thermal stability of freeze-dried colostrum was reported to increase from 109°C on day 1 to 132.4°C on day 5, according to differential scanning calorimetry analysis (Umar et al., Reference Umar, Ruktanonchai, Makararpong and Anal2023. Additionally, simulated in vitro gastrointestinal digestion showed that immunoglobulins in freeze-dried colostrum were partially resistant to gastrointestinal digestion, resulting in a considerable proportion of bioaccessible immunoglobulins, particularly in colostrum collected during the first 2 days postpartum (Umar et al., Reference Umar, Ruktanonchai, Makararpong and Anal2023). A linear increase in colour difference and a slight decrease in IgG concentration were detected in freeze-dried colostrum powder packaged in ALPE bags and observed during storage at 25°C, 50% RH for 60 days. The shelf life was 243 days (Yu et al., Reference Yu, Zheng and Li2013). Mehra et al. (Reference Mehra, Kumar, Singh, Kumar, Rathore, Nayik, Alabdallah, Monteiro, Guiné and Kumar2022) obtained colostrum whey powder by THE freeze-drying method. It was stated that freeze-dried colostrum powder contains many amino acids, minerals and IgG, which can be used in functional product development. The physicochemical properties and antioxidant activities of dromedary colostrum powder and milk powder produced by freeze drying were compared in a study. When antioxidant properties were examined, DPPH and ABTS radical scavenging activities were almost similar, whereas both ferric reducing power and ferrous chelating activity (FRAP) were reported to be more pronounced in dromedary skimmed colostrum powder (Oussaief et al., Reference Oussaief, Jrad, Dbara, Khorchani and El Hatmi2021). Sharma et al. (Reference Sharma, Mondal, Raguvaran, Das and Yadav2020) investigated the effects of freeze drying (−40°C) on the immunoglobulin and total antioxidant contents of bovine colostrum. The freeze-drying process caused an average decrease of 26.05% in IgG content. Bovine colostrum’s average radical scavenging activity was 50.46%, and 32.75% in freeze-dried samples.

Colostrum powder should be brought into a suitable form for purposes other than a food matrix. For this purpose, in one study, colostrum was prepared in a gelatin–gum Arabic matrix by a complex coacervation method and then freeze-dried. The obtained colostrum powder was added to traditional clay masks, peelable gel masks and sleeping gel mask formulations and its usage potential was investigated (Chuesomboon et al., Reference Chuesomboon, Rades and Chaiyana2025).

Despite all these advantages, freeze drying is an expensive process as it requires a vacuum environment for a long period, demanding high energy consumption (Castro-albarrán et al., Reference Castro-Albarrán, Aguilar-Uscanga, Calon, St-amour, Solís-Pacheco, Saucier and Ratti2016).

Fluid bed drying

The fluidized bed dryer is considered a post-drying process that can give instant properties to colostrum after it has been converted into powder form. Fluidized bed technology is used in applications such as drying, agglomeration and encapsulation in the food, pharmaceutical and chemical sectors (Atalar, Reference Atalar2021). The general design of the fluidized bed system is as shown in Figure 1.

Figure 1.

General design of a fluidized bed dryer (created with ChatGPT).

Figure 1 Long description

The design of a fluid bed dryer is illustrated, detailing the flow and components involved in the process. On the left, a container labeled ′Binder solution (colostrum or additive)′ is connected to a peristaltic pump. This pump directs the binder solution to an atomizing nozzle at the top of a large vertical chamber. Inside this chamber, fluidized particles are shown, with arrows indicating the movement of binder droplets and powder particles. Below the chamber, an ′Air distributor plate′ is present, leading to a ′Product outlet (agglomerated powder)′ at the bottom. To the right, a blower is connected to the chamber, supplying ′Heated air inlet (temperature controlled)′ through a pipe. This air moves upwards, passing through the fluidized particles and exiting as ′Exhaust air′ at the top, which is directed into a filter bag. The diagram includes a legend indicating the symbols for ′Binder solution′, ′Process air′, ′Powder particles′ and ′Binder droplets′.

Fluidized bed drying can be performed as a batch or continuous process. In a fluidized bed dryer, the air has a higher velocity than the settling velocity of the solid particle to be fluidized, so the solid particle is blown away and remains suspended. This situation is called the fluidized state. The use of hot air in a fluidized bed increases the drying speed of food. The fluidized bed contains a stainless-steel chamber with a removable perforated bottom. The product to be dried is placed in this chamber and air is supplied from below and heated to the desired temperature with heaters (Senapati et al., Reference Senapati, Varshney, Sharma and Patel2021). The fluidized bed process is classified as top spray, bottom spray, Wurster spray and tangential spray according to the position of the nozzle (Pawar et al., Reference Pawar, Surwase, Bhamare and Pagar2020; Teunou and Poncelet, Reference Teunou and Poncelet2002).

Agglomeration encourages particles to bind in a controlled manner and form larger aggregates, improving particle properties. The most common method used for agglomeration in industry is the fluidized bed agglomeration process. This process occurs through two mechanisms: (1) the aggregation of particles by spraying the binder solution (wet agglomeration) and (2) fluidization of the powder with hot air and the formation of more stable and drier agglomerated particles (dry agglomeration) (Cardona et al., Reference Cardona, Cortés-Rodríguez and Galeano2022). In particular, powders obtained by spray drying have very small particle sizes and low densities, resulting in poor fluidity and poor reconstitution properties (solubility, wettability, dispersibility, etc.). In this case, the agglomeration process should be applied to improve the fluidity and other properties of the powder particles after spray drying (Bozkurt et al., Reference Bozkurt, Altay, Koç and Ertekin2020).

Encapsulation/coating using a fluidized bed dryer increases molecules’ stability and improves bioactive molecules’ functional properties in general (Bellumori et al., Reference Bellumori, De Marchi, Mainente, Zanoni, Cecchi, Innocenti, Mulinacci and Zoccatelli2021). It is a particularly suitable method for encapsulating solid particles (Lin et al., Reference Lin, Meletharayil, Kapoor and Abbaspourrad2021). This method has been used to mask odour or bad taste, protect active ingredients against environmental conditions such as oxygen, light and moisture, and improve the flowability of powders (Chen et al., Reference Chen, Yang, Mujumdar and Dave2009). In the fluidized bed encapsulation process, the particles to be coated are fluidized using hot air in a coating chamber. A multilayer structure is created by spraying the coating solution onto the surface of particles, which are kept in motion in the fluidized bed using a nozzle and drying them. The coating material can be a concentrated solution, dispersion or an emulsion. This method was developed for pharmaceutical applications but has also been applied to functional additive ingredients in the food industry (Coronel-aguilera and San Martín-gonzález, Reference Coronel-aguilera and San Martín-gonzález2015; Lin et al., Reference Lin, Meletharayil, Kapoor and Abbaspourrad2021). Although the agglomeration process does not change the chemical content (Murrieta-pazos et al., Reference Murrieta-pazos, Gaiani, Galet and Scher2012), it does modify the surface properties when different binders are used (Szulc and Lenart, Reference Szulc and Lenart2013).

Fluidized bed dryers are used to produce instant powders, such as dairy-based milk powders, cereal powders, gum powders, and fruit and vegetable powders in the food industry. If it is focused on dairy products, there are studies in the literature that have used fluidized bed dryers to develop instant properties to milk-based products such as whole/semi-skimmed milk powder (Barkouti et al., Reference Barkouti, Turchiuli, Carcel and Dumoulin2013), milk protein isolate (Ji et al., Reference Ji, Cronin, Fitzpatrick, Fenelon and Miao2015, Reference Ji, Fitzpatrick, Cronin, Fenelon and Miao2017), whey protein isolate (Ji et al., Reference Ji, Fitzpatrick, Cronin, Fenelon and Miao2017), Yoghurt powder (Atalar and Yazici, Reference Atalar and Yazici2018) and dairy-based multi-component powders (Szulc and Lenart, Reference Szulc and Lenart2013). These studies have demonstrated that a fluidized bed dryer can produce milk-based products with increased particle size, improved wettability, higher porosity and instant properties.

The schematic representation of the agglomeration and encapsulation/coating processes carried out with the fluidized bed dryer is shown in Figure 2.

Figure 2.

The schematic representation of the agglomeration (a) and encapsulation/coating (b) processes by a fluidized bed dryer (created with ChatGPT).

Figure 2 Long description

The image consists of two diagrams illustrating different mechanisms. The first diagram, labeled ′Agglomeration Mechanism,′ shows six steps: 1. Powder particles, 2. Binder spraying, 3. Liquid bridge formation, 4. Part icle growth, 5. Solid bridge formation and 6. Porous agglomerate. Each step is represented by a visual of particles and arrows indicating progression. Powder particles are shown as small circles, binder droplets as dotted lines, liquid bridges as connected circles, solid bridges as clustered particles and porous agglomerates as larger clusters. The second diagram, labeled ′Coating Mechanism,′ includes five steps: 1. Core particle, 2. Binder spraying, 3. Film spreading, 4. Drying and 5. Uniform coated particle. Core particles are depicted as single circles, binder spraying as dotted lines, film spreading as shaded circles, drying as lighter circles and uniform coated particles as blue circles. The diagrams use visual symbols to represent powder particles, binder droplets, liquid bridges, solid bridges and coating layers, with arrows indicating the process flow.

Fluidized bed dryers are extensively employed not only for encapsulation and surface coating applications but also as a post-processing technique to enhance the instant characteristics – such as wettability, dispersibility and solubility – of spray- or freeze-dried powders. In particular, powders obtained by spray drying have very small particle sizes and low densities, resulting in poor fluidity and poor reconstitution properties (solubility, wettability, dispersibility, etc.). In this case, the agglomeration process should be applied to improve the fluidity and other properties of the powder particles after spray drying (Bozkurt et al., Reference Bozkurt, Altay, Koç and Ertekin2020). In another study, spray-dried Yoghurt powders were subjected to an agglomeration process in fluidized bed dryers to improve their hydrophilic character and to make them more soluble in water (Atalar and Yazici, Reference Atalar and Yazici2019). For wet agglomeration, freeze-dried colostrum powder was agglomerated with different binders (distilled water, lactose, maltodextrin and sucrose) using a fluidized bed dryer (Özgeçen, Reference Özgeçen2024). It was reported that the solubility of colostrum powder, which was 74%, increased to 83% with the fluidized bed dryer. Furthermore, the Carr index, an indicator of fluidity, decreased from 41% to 20%, indicating increased fluidity of the agglomeration in the fluidized bed dryer. As a result, agglomerated colostrum powders with improved fluidity and thermal properties were obtained (Özgeçen, Reference Özgeçen2024). In another study, where boza beverage was processed into instant form, it was reported that the wetting time of boza powder obtained by the spray-drying method was 335 s, while the wetting time of agglomerated boza powder was 26–39 s (Gül et al., Reference Gül, Atalar, Özgeçen, Gül, Törnük, Sert and Yazıcı2025). The angle of repose below 30° indicates good fluidity. In a study in which mushroom powder was attempted to be instantized, the angle of repose of the control mushroom powder was 52.25°, and it was reported to be in the medium fluidity class. After the fluidized bed dryer agglomeration process, the angle of repose of the mushroom powder was determined to be 21.98–26.1° (Atalar et al., Reference Atalar, Kurt, Saricaoğlu, Gül and Gençcelep2021). All these studies have paved the way for the fluidized bed dryer to improve the instant properties (high solubility, high wettability, high flowability, etc.) of the colostrum powder. Powders exhibiting enhanced instant properties are characterized by superior dispersibility and solubility in various food matrices or application environments, facilitating processing operations and contributing positively to consumer acceptance (Atalar, Reference Atalar2021).

The main advantages of fluidized bed drying include a large contact surface area between solid and gas, rapid heat and moisture transfer, short drying time, instant powder production with improved properties and prevention of overheating due to continuous mixing with air (Daud, Reference Daud2008; Sivakumar et al., Reference Sivakumar, Saravanan, Elaya Perumal and Iniyan2016). However, there are also some limitations to the application of fluidized bed technology. It is difficult to reliably predict the performance of a fluidized bed dryer before pilot plant trials are conducted. This is because reliable mathematical models for fluidized bed dryers are not available. Therefore, a fluidized bed dryer used to dry a particular material can be scaled using experimental pilot plant data, not mathematical models (Daud, Reference Daud2008). Another disadvantage is that fragile and fine solid particles can easily be entrained in the gas, leading to product loss (Sivakumar et al., Reference Sivakumar, Saravanan, Elaya Perumal and Iniyan2016). Furthermore, particle aggregation can significantly alter the product size distribution. A wide particle size distribution can also reduce fluidization quality and consequently product quality (Daud, Reference Daud2008; Sivakumar et al., Reference Sivakumar, Saravanan, Elaya Perumal and Iniyan2016).

Comparing methods

Spray and freeze drying are commonly used to produce powdered products from liquids. On the other hand, the fluidized bed dryer uses powdered food products, not liquids. It is a post-drying process used to improve the instant properties of powdered products. The methods used to obtain instant colostrum powder are given in Figure 3.

Figure 3.

Drying methods used to obtain instant colostrum powder.

Figure 3 Long description

A textual illustration arranged as a process flow with arrows connecting labelled items. A boxed section contains three headings: Nutritional composition, Immune factors, Growth Factors. Under each heading are small scientific style icons. A central label reads, COLOSTRUM. Nearby are a cow icon and a container with liquid. A heading reads, Drying methods. Three labelled steps are shown with equipment icons: Spray drying, Freeze drying, Fluid bed drying. A label below reads, Colostrum powder. A label at the end reads, Instant colostrum powder.

Studies in the literature compare the properties of colostrum powders dried by freeze-drying and spray-drying methods. In the study conducted by Sotudeh et al. (Reference Sotudeh, Rabbani Khorasgani, Etemadifar and Zarkesh-esfahani2018), spray-drying and freeze-drying processes were applied to the first milking bovine colostrum samples after birth and investigated their effects on IgG content. When the average IgG contents of bovine colostrum samples were examined, the order from the highest IgG content to the lowest was the control sample, freeze-dried and spray-dried, respectively. Although there was no significant difference between the samples dried with different methods, a smaller loss in IgG content was observed in the freeze-dried samples. In a study investigating the effects of different drying methods (freeze drying and spray drying) on colostrum powder, it was concluded that the drying methods did not result in a statistically significant difference in the activity of IgG protein. However, the highest lactoferrin content was detected in freeze-dried colostrum powder (Wu, Reference Wu2024). In the study by Borad et al. (Reference Borad, Singh, Meena, Arora, Raju and Sabikhi2021), spray drying was applied to fat-free diluted colostrum and retentate colostrum whey samples under different conditions. Freeze-dried samples were used as controls. As a result, the IgG contents of spray-dried samples were lower than those of freeze-dried control samples. It was observed that different inlet air temperatures did not significantly affect IgG contents. Furthermore, when examined in terms of technofunctional properties, the loose bulk density, fluidity, wettability and solubility properties of freeze-dried colostrum were superior to those of spray-dried colostrum powder. Salar et al. (Reference Salar, Jafarian, Mortazavi and Nasiraie2021) investigated the effects of different drying methods (spray drying and freeze drying) and different pasteurization conditions (57°C, 60°C and 63°C for 30, 45 and 60 min) applied to bovine and buffalo colostrum samples on bioactive protein contents (IgG and lactoferrin) and antioxidant activity. When the effect of drying methods on bioactive proteins of colostrum was examined, a slight protein denaturation occurred in both drying processes. However, the stability of lactoferrin against drying processes was found to be greater than that of IgG. When the effect of drying method on antioxidant activity was examined, there was no significant difference between the radical scavenging activities of spray-dried and freeze-dried samples. However, there was a smaller decrease in antioxidant activity compared to spray drying. It was observed that freeze drying did not have a significant effect on the antioxidant activity of colostrum. The ability of colostrum obtained by different drying methods to pass through the intestinal wall of calves was compared. For this purpose, Holstein calves were fed two different colostrum powders with the same IG concentration: commercially dried and freeze-dried. It was reported that the highest absorption occurred in calves fed freeze-dried colostrum (Wereme et al., Reference Wereme, Strabel, Grongnet and Piot2001). Fatima et al. (Reference Fatima, Sajid, Saima, Nadeem, Ahmad, Mehmood, Zubair Khalid, Ali Alharbi, Ansari and Kasongo2024) examined bovine colostrum’s nutritional and functional properties by spray-drying and freeze-drying methods. The results showed that freeze-dried bovine colostrum exhibited higher levels of defence proteins (IgG and IgA) and DPPH. Spray-dried samples, on the other hand, exhibited superior properties in terms of some antioxidant properties (FRAP, TPC and ABTS). Sensory evaluation revealed that spray-dried colostrum received higher scores for flavour and aroma, while freeze-dried samples were preferred for appearance. In a study, equine colostrum was dried using the freeze-drying method. A slight decrease (6.55%) in IgG concentration was reported after the freeze-drying process (De Lima et al., Reference De Lima, De Sobral, De França Queiroz, Chinelate, Porto, Oliveira and Carneiro2024).

In summary, while spray drying is a fast and cost-effective method, it can cause a decrease in the amount of IgG and other immune proteins due to high temperatures. Another drying method, freeze drying (lyophilization), is slower and more costly, but studies have reported superior protein preservation and functional properties.

The advantages and limitations of these methods are listed in Table 3.

Table 3.

The advantages and limitations of drying methods

Table 3 Long description

Drying methods are compared across two columns, Advantages and Disadvantages, for freeze drying, spray drying, and fluid bed drying. Freeze drying advantages list high yield, suitability for temperature sensitive components, minimal structure change, and high porosity and rehydration capacity of products; disadvantages list high operating and capital costs and being a time consuming process. Spray drying advantages list producing products with small particle sizes, excellent quality powder, high temperature operation, suitability for high moisture foods, and large contact surface area; disadvantages list low product yield between 20 and 70 percent, degradation of thermolabile compounds due to exposure to high temperature, product and quality losses, and difficulty drying sugar rich foods due to stickiness. Fluid bed drying advantages list superior heat mass transfer, highly soluble powders, large contact surface area between solids and gas, less drying time, high level intermixing of particulate phase, and preventing overheating due to continuous mixing; disadvantages list higher capital and operational costs requiring a more powerful compressor, a broader particle size distribution, too much undesirable dust, and restriction on particle size.

Colostrum powder as a food ingredient or food supplement

Due to its rich bioactive compound composition, colostrum is considered a high-value functional food ingredient. When available in surplus quantities, it should be subjected to appropriate processing and preservation techniques – such as drying, encapsulation or formulation into derivative products – to enhance its shelf life and enable its incorporation into functional food matrices intended for human consumption (Ceniti et al., Reference Ceniti, Costanzo, Morittu, Tilocca, Roncada and Britti2023). Foods prepared using colostrum are given in Table 4.

Table 4.

Foods prepared using colostrum

Table 4 Long description

Columns list colostrum form, colostrum source, final product, country, and references for 20 entries. Colostrum form is most often fresh colostrum, with additional entries for steamed bovine colostrum, colostrum powder, colostrum powder with 30 percent IgG, freeze dried colostrum powder, and freeze dried colostrum powder. Colostrum source is usually bovine or cow, with specific sources including cow and buffalo, Jersey cow, and buffalo. Final products include Khees in Northern India, Avuz in Turkiye, paneer based products described as sweet rice and tikka masala in India, pudding described as soft gel in Germany, fermented product in India, and infant formula in Iraq. Yoghurt appears in Romania and Egypt, plus Greek style yoghurt in Brazil, and yoghurt and kefir in Turkiye. Cheese products include spreadable cheese in Mexico and fresh and matured cheeses in Brazil, plus butter and milk beverages in Brazil. Fermented beverage appears twice in Romania, and ice cream appears in the USA and Egypt, with antimicrobial gummy candy listed in Lithuania.

Hege et al. (Reference Hege, Ghebremedhin, Joshi, Schreiber and Vilgis2021) produced colostrum pudding and investigated the properties of colostrum soft gel. Mouton and Aryana (Reference Mouton and Aryana2015) produced slower-melting ice cream with increased aerobic microorganism count and apparent viscosity using colostrum powder with 30% IgG. In another study on the use of colostrum milk in ice cream production, colostrum-fortified ice creams with higher protein, carbohydrate and antioxidant activity were obtained as the colostrum ratio used increased. It was also reported that ice creams with colostrum added had a low melting rate and enhanced textural properties (Saleh et al., Reference Saleh, Moussa, Hassabu and Ewis2020). A study used colostrum in Yoghurt production to increase biological and nutritional benefits (Ahmadi et al., Reference Ahmadi, Velciov, Scurtu, Ahmadi and Olariu2011). In another study where colostrum milk was used in Yoghurt production, Greek-type Yoghurts with high fat and protein content and sensory acceptance of over 70% were produced (Silva et al., Reference Silva, Anaya, Bezerra, Macedo, Urbano, Borba, Barbosa, Ramalho, Cipolat-gotet and Galdino2021). A fermented product was developed using different ratios of cow milk to colostrum. According to sensory results, the fermented colostrum product scored highest (Nazir et al., Reference Nazir, Pal and Manzoor2018). Saleh et al. (Reference Saleh, Hassabo, Hassabo and Ewis2019) investigated the physical, chemical, microbiological and sensory properties of stirred Yoghurt products fortified with different proportions (10%, 20% and 30%) of cow and buffalo colostrum. It was reported that, with the increase in the colostrum ratio, there was an increase in coagulation time, protein content, viscosity, water-holding capacity and antioxidant activity and that colostrum-fortified Yoghurt has the potential for increased demand and consumer appeal. Functional Yoghurt was prepared using 3% fat buffalo milk, 5% date syrup and bovine colostrum (5%, 10% and 15%) (Abdel-ghany and Zaki, Reference Abdel-ghany and Zaki2018). It was reported that adding date syrup and bovine colostrum significantly increased the content of total dry matter, total protein, IgG, lactoferrin and minerals compared to the control. It was reported that the addition of date syrup and bovine colostrum significantly increased the content of total dry matter, total protein, IgG, lactoferrin and minerals compared to the control. It was also reported that Yoghurt supplemented with 10% and 15% bovine colostrum had significantly higher viscosity values than other samples and Yoghurt containing 15% bovine colostrum had significantly lower syneresis than other Yoghurt samples at 12 days of storage (Abdel-ghany and Zaki, Reference Abdel-ghany and Zaki2018). Milk beverages were developed from bovine colostrum by Saalfeld et al. (Reference Saalfeld, Pereira, Silveira, Diniz, Kringel, Alves, Gularte and Leite2012). It was reported that bovine colostrum has superior protein, fat, ash and dry matter percentages and nutritional quality to milk, and is beneficial for human diets. The study was conducted by Ayar et al. (Reference Ayar, Sıçramaz and Çetin2016) to determine the effect of freeze-dried bovine colostrum on the lactic flora of Yoghurt and kefir. It was reported that the number of Streptococcus thermophilus and Lactobacillus bulgaricus was higher in Yoghurt samples with added colostrum powder. They concluded that colostrum could be added to Yoghurt and kefir to increase their functional properties. Colostrum kefir was produced by Windayani et al. (Reference Windayani, Kurniati and Listiawati2019) using 250 ml of colostrum and 20% kefir grains through fermentation at 28°C for 48 h under optimum physicochemical conditions (pH: 3.31–3.65; lactic acid content: 1.96–2.83%; alcohol content: 0.38–0.59%; specific gravity: 1.030–1.046 mg/ml) and organoleptic properties (yellow-orange colour, sour, soft drink and intense, typical kefir aroma). It has been reported that the functional product obtained by fermenting bovine colostrum with kefir grains and Candida lipolytica strains exhibits Angiotensin-Converting Enzyme (ACE) inhibitory and antioxidant activity. This fermented colostrum enables the diversification of value-added dairy products with functional properties that improve human health (Gaspar‐pintiliescu et al., Reference Gaspar‐pintiliescu, Oancea, Cotarlet, Vasile, Bahrim, Shaposhnikov, Craciunescu and Oprita2020). In the study conducted by Cotârleţ et al. (Reference Cotârleţ, Vasile, Gaspar-pintiliescu, Oancea and Bahrim2020), the tribiotic (pre-, pro- and postbiotic) functional product obtained by two-stage biotransformation (enzymatic conversion and fermentation) of bovine colostrum using starter cultures (bacteria and yeasts) exhibited radical scavenging and ACE-inhibitory activities, thus providing a new perspective for the development of colostrum-based nutraceutical formulations. Bartkiene et al. (Reference Bartkiene, Ruzauskas, Lele, Zavistanaviciute, Bernatoniene, Jakstas, Ivanauskas, Zadeike, Klupsaite and Viskelis2018) developed an antimicrobial gummy candy based on combinations of freeze-dried fermented bovine colostrum, essential oils and probiotic lactic acid bacteria. According to the study, gummy candies with good texture and high general acceptability could be developed with the formulation containing fermented bovine colostrum (3%) together with thyme, tangerine and grapefruit essential oils (2%–2%–2%), and such antimicrobial candies could reach the nutraceutical form that consumers would prefer (Bartkiene et al., Reference Bartkiene, Ruzauskas, Lele, Zavistanaviciute, Bernatoniene, Jakstas, Ivanauskas, Zadeike, Klupsaite and Viskelis2018). In another study, functional spreadable cheese with high yield and protein content was produced using colostrum milk (Reyes-portillo et al., Reference Reyes-portillo, Quintero-Lira, Piloni-Martini, Fajardo-espinoza, Hernández-Sánchez and Soto-Simental2021). In a study in which fresh and matured cheese was produced using various ratios of cow’s milk to colostrum, all cheeses received acceptable approval ratings. In contrast, the cheese sample containing 25% colostrum received the highest approval rating (Barbosa et al., Reference Barbosa, Anaya, Macêdo, Coelho, Cipolat-gotet, Silva, Araújo, Chagas, Oliveira and Boari2023). In a study investigating the effectiveness of infant formula containing anti-E. coli colostral antibodies from hyperimmunized cows in preventing diarrhoea in infants and children, Tawfeek et al. (Reference Tawfeek, Najim and Al-mashikhi2003) reported that the rate of diarrhoea in infants fed with formula containing colostral antibodies was lower than in infants receiving control formula. Diarrhoea attacks were shorter in infants receiving supplemented formula.

Traditional products are also produced using colostrum. For instance, khees is a traditional dessert prepared in India that uses the gelling properties of colostrum. It is also known as kharwas, posu or ginnu in different parts of India. Colostrum from the first to fourth milking is used to prepare khees. Sugar is usually added to the colostrum to give the desired flavour, and saffron or cardamom is used as a flavouring agent. The mixture is then kept in a boiling water bath. Cuttable khees is obtained with gelation in about 15 min (Manikant Kumar and Sudhir Uprit, Reference Manikant Kumar and Sudhir Uprit2014; Poonia and Dabur, Reference Poonia and Dabur2012). The paneer-based sweet rice and tikka masala, another popular Indian dish, recipes were enriched by adding steamed cake of bovine colostrum (Dande and Nande, Reference Dande and Nande2020). Ağuz, also called avuz in various regions of Türkiye, is a paste-like food consumed as breakfast by adding salt to the colostrum strained from calving cows and cooking it, and then serving it with sugar on it (Karlıdağ, Reference Karlıdağ2020).

Although colostrum has attracted considerable interest as a functional food component, its application in human food systems requires regulatory frameworks worldwide. The use of bovine colostrum in human food and nutraceutical applications is subject to varying regulatory frameworks across different countries. These regulatory differences influence product development, market access and standardization of colostrum-based functional foods. Therefore, regulatory harmonization and clearer product-specific guidelines would be beneficial to support the safe and consistent use of colostrum in human food systems and functional food development.

Conclusion and future perspectives

In recent years, colostrum has become the subject of various scientific studies because it is an excellent source of biologically active components. The immune factors in colostrum have the potential to be used as immunological additives in infant formula and other food supplements. Research on the development of functional foods and nutraceuticals has focused on the ability of colostrum to provide health benefits to the adult population. Researchers have shown that colostrum and its role in neonatal nutrition may be effective against adult disease conditions such as Alzheimer’s disease, microbial infection, diarrhoea and gastrointestinal disorders. Colostrum preparations are safe, effective, natural, readily bioavailable and may offer disease prevention and treatment options for neonates and adults. They also have high potential for use as a natural ingredient in formulating innovative functional foods and nutraceuticals.

Colostrum milk needs to be processed into a form suitable for human consumption, not only for the nutrition and immune enhancement of the offspring but also for human benefit. Colostrum milk can be added to different food formulations to create functional foods for human consumption. For this purpose, it is important to transform colostrum into a form with a long shelf life suitable for food matrices as a functional ingredient. In this review, fluidized bed drying technology emerges as a promising post-processing approach to improve the instant properties such as dispersibility, wettability and solubility of dried powder products. As evidenced by previous studies, this method can significantly enhance the physical functionality of spray- or freeze-dried powders, contributing to better reconstitution properties in food systems. Despite its proven advantages, the application of fluidized bed drying to bovine colostrum powder remains relatively underexplored. Studies should monitor the changes in nutritional and biological substances in colostrum after fluidized bed drying. Also, studies should focus on the optimization of process parameters within fluidized bed systems, including investigations on both dry and wet agglomeration techniques. The impact of critical variables such as inlet air temperature, binder type and concentration, atomization rate, and fluidization air velocity on particle morphology, powder flowability, and rehydration behaviour are also issues that need to be investigated. Optimizing process parameters such as inlet air temperature, binder concentration and fluidization air flow can yield colostrum powders with superior technological and functional properties. In addition, the selection of appropriate binder agents (e.g. maltodextrin, lactose and sucrose) and their influence on the physicochemical stability of the colostrum powder during storage merit detailed evaluation. Monitoring changes in moisture content, hygroscopicity, bulk density and IgG retention over time would provide valuable insights for shelf-life prediction and quality control.

Ultimately, the outcomes of such studies are expected to support the development of instant colostrum-based formulations with superior functional properties, thereby facilitating their incorporation into various food matrices, such as ready-to-drink beverages, infant formulas or clinical nutrition products, and enhancing consumer acceptability and product marketability.