Physical and morphological properties of whole milk powder produced by dynamic freeze-drying

This study was designed to compare the quality characteristics of spray-dried (SD) and freeze-dried (FD) Pueraria thunbergiana extracts powder hot water extracts. Quality characteristics of the SD and FD powder including moisture content, color value, water absorption index, water solubility index, dynamic angle and antioxidant activities were evaluated. The moisture content of SD powder (1.50%) was lower than that of FD powder (2.92%). L* and b* values of SD powder was lower than of FD powder. The water absorption index was higher in FD powder (1.40) and water solubility index in SD powder (94.10%) was higher than that FD powder (90.69%). Dynamic angle of SD powder (36.46°) was higher than that of FD powder (33.30°). The DPPH radical scavenging activities of 5 mg/mL solution of SD powder and FD powder were 85.38 mg/mL, 59.38 mg/mL, respectively. And, the same trend was observed for the ABTS radical scavenging activities of the drying powder as that observed for their DPPH radical scavenging activities. There were relatively higher contents of phenolic compounds in SD powders than in FD powders. In conclusion, spray-dried Pueraria thunbergiana extracts showed the high WSI, polyphenol, DPPH and ABTS radical scavenging activities and low moisture content and dynamic angle than freeze dried powder.

The main goal of this study was to compare glass transition temperature (Tg)– aw relations, critical water activity (awc) values, particle morphology, moisture sorption behavior, total phenolic content, and stability of freeze-dried (FD) and spray-dried (SD) sour cherry powders. The Tg of the SD and FD powders decreased from 57°C to 14°C and from 47°C to 15°C, respectively, as the aw increased from 0.03 to 0.35. Higher Tg values were observed for SD powder compared to FD powder in the aw range (0.03–0.35) covered in this work. The awc was 0.29 for SD powder and 0.26 for FD powder. Scanning electron microscopy images showed that FD sour cherry powder exhibited a more porous morphology compared to SD powder. Total phenolic content of SD and FD powders was found to be similar (16.1 ± 0.3 mg GAE/g sour cherry dry matter). The results of this study suggest that physicochemical properties of spray-dried sour cherry powders are comparable to those obtained by freeze drying. Practical applications Stability of fruit-based powders is mostly determined by their Tg and awc values. Such data are scarce for sour cherry powders. The present study provides useful information on Tg and awc of sour-cherry powders produced with two drying methods. The results of this study clearly demonstrated that properties of spray-dried sour cherry powders compare favorably with those obtained by freeze drying. The findings of this study can be useful in determination of storage conditions for commercial sour cherry powders based on the awc values.

Effect of drying methods on the physical properties and microstructures of mango (Philippine ‘Carabao’ var.) powder

Effect of spray and freeze drying on physico-chemical, functional, moisture sorption and morphological characteristics of camel milk powder

This study was designed to compare the quality characteristics of spray-dried (SD) and freeze-dried (FD) powders prepared with hot water extracts of sea mustard (Undraia pinnatifada) and sea tangle (Laminaria longissima). The moisture content of FD seawed was lower than that of SD, and sea mustard had a higher overall moisture content than sea tangle. The alginic acid content of SD seaweed was significantly higher than that of FD seaweed for both species. There were relatively higher contents of phenolic compounds in SD powders than in FD powders. DPPH radical scavenging ability was significantly greater in SD seaweed, and also, SOD-like activity in SD powders was higher than those of FD powders. However, the nitrite scavenging activity of FD powders of sea mustard (10 mg/mL) was higher than that of SD. In conclusion, spray-dried sea mustard and sea tangle extracts exhibited higher physiological functionalities than their freeze-dried counterparts.

The aim of this study was to evaluate the effect of air outlet temperature (75 and 85 °C) and milk type on proximate composition, water activity, particle size distribution, color, and rehydration ability of spray-dried skim dromedary and cow’s milk powders. While the water activity of powders was close to 0.4 when spray-dried at 75 °C air outlet temperature, it ranged from 0.2 to 0.3 for a production at 85 °C air outlet temperature. Skim dromedary milk powder had a lower water activity than skim cow’s milk powder after spray-drying at 85 °C air outlet temperature. Spray-drying yields were greater at the higher air outlet temperature (85 °C) for both skim milk powders. The particle size distributions of spray-dried skim milk powders were centered around 14–20 µm. The particles of skim dromedary milk powders were smaller than those of skim cow’s milk powders as skim dromedary milk was less viscous, leading to smaller sprayed droplets. No significant influence of spray-drying conditions on particle size distribution was observed for dromedary milk powders. Regardless of the spray-drying conditions and the milk type, the produced powders were very bright and had a low color saturation. Scanning electron microscopy images showed that spray-dried powders appeared as agglomerates of small particles with angular shapes rather than individual particles. All investigated spray-dried powders were considered non-wettable, hardly dispersible, and fairly soluble. Skim dromedary milk powder produced at 85 °C air outlet temperature showed a significantly higher solubility index than the same formulation spray-dried at 75 °C outlet air temperature. The opposite was obtained for skim cow’s milk powder. These results demonstrated that the outlet drying air temperature significantly influenced water activity, spray-drying yield and solubility of spray-dried dairy powders.

Reduction of water activity in the formulations of mosquito biocontrol agent, Bacillus thuringiensis var. israelensis is very important for long term and successful storage. A protocol for spray drying of B. thuringiensis var. israelensis was developed through optimizing parameters such as inlet temperature and atomization type. A indigenous isolate of B. thuringiensis var. israelensis (VCRC B-17) was dried by freeze and spray drying methods and the moisture content and mosquito larvicidal activity of materials produced by the two methods were compared. The larvicidal activity was checked against early fourth instars Aedes aegypti larvae. Results showed that the freeze-dried powders retained the larvicidal activity fairly well. The spray-dried powder moderately lost its larvicidal activity at different inlet temperatures. Between the two types of atomization, centrifugal atomization retained more activity than the nozzle type atomization. Optimum inlet temperature for both centrifugal and nozzle atomization was 160 degrees C. Keeping the outlet temperature constant at 70 degrees C the moisture contents for the spray-dried powders through centrifugal atomization and freeze-dried powders were 10.23% and 11.80%, respectively. The LC(50) values for the spray-dried and freeze-dried powders were 17.42 and 16.18 ng/mL, respectively. Spore count of materials before drying was 3 x 10(10) cfu/mL and after spray drying through nozzle and centrifugal atomization at inlet and outlet temperature of 160 degrees C/70 degrees C were 2.6 x 10(9) and 5.0 x 10(9) cfu/mL, respectively.

Egg white protein (EWP) was phosphorylated with Sodium Tripolyphosphate (STP) at pH 4.5. Freeze drying and spray drying were used for drying purpose and the effects of these drying methods on the functional properties were investigated. The functional properties of native and modified proteins were also determined. The results demonstrated that phosphorylation of EWP markedly improved its functional properties, and that it was more effective for the food industry. The freeze-dried STP-EWP powders were superior in terms of solubility, emulsion stability, water holding capacity, oil and water absorption capacity and heat gel strength than spray-dried STP-EWP powders. The results in viscosity showed no significant differences between freeze-dried and spray dried. The spray-dried powders were better in terms of foaming ability and foam stability than freeze-dried powders. However, the spray drying required the longest time to produce. Freeze drying was found to be the best method in terms of production of modified EWP powders with superior functional properties. Keywords: freeze drying, spray drying, egg white protein, phosphorylation, functional properties DOI: 10.3965/j.ijabe.20150804.1942 Citation: Liu L L, Wang H, Ren G Y, Duan X, Li D, Yin G J. Effects of freeze-drying and spray drying processes on functional properties of phosphorylation of egg white protein. Int J Agric & Biol Eng, 2015; 8(4): 116－123.

Development of oral solid dosage forms containing biologics has attracted intense interests recently due to the high patient convenience and the commercial potential of related products. The aim of this study was to understand how the difference in the particle properties prepared using two different drying principles, i.e. freeze-drying and spray-drying, may influence the compaction behavior of particulate protein systems. Here, trypsin was used as a model protein drug and lactose as a filler. The raw freeze-dried (FD) powder composed mostly of trypsin and lactose was dissolved in Milli-Q water and processed by spray-drying to produce spray-dried (SD) powder. Meanwhile, the raw FD powder was micronized by a ball mill into fine ball-milled (BM) powder with a comparable particle size to that of SD powder. Next, the FD, BM and SD powders were characterized with regard to morphology, residual moisture content (RMC), solid form, and surface chemistry using scanning electron microscope (SEM), thermogravimetric analysis (TGA), X-ray powder diffraction (XRPD), and X-ray photoelectron spectroscopy (XPS), respectively. Subsequently, a compaction simulator was employed to prepare tablets within the compaction pressure range of 25 to 400 MPa. The results showed that FD and BM powders could be compressed into tablets within the investigated compaction pressure range. In contrast, tablets compacted from SD powder displayed capping/lamination tendency under high compaction pressures and thus had poor tabletability. XPS analyses revealed that there were more surface enrichments of trypsin in the SD powder compared to that of FD powder. It implies that there would be more hydrophobic inter-particulate trypsin-trypsin interactions and less hydrophilic lactose-lactose interactions during the compression of SD powder compared to the compaction of FD powder. The weak hydrophobic inter-particulate trypsin-trypsin interactions may not be maintained during the decompression phase especially when compacted at high compaction pressure ranges, resulting in capping/lamination of the SD tablets. This study demonstrates that the two drying principles, i.e. freeze-drying and spray-drying, can result in different particle properties of biologics, which can in turn influence the tabletability of the resulting solid materials.

Two plant-based emulsifiers, soybean lecithin and pea protein isolate, were studied for their emulsifying and encapsulating capacities of an antimicrobial molecule, trans-cinnamaldehyde (TC), at two different pH values, three and seven, and after drying with two different techniques, spray-drying and freeze-drying. To characterize the obtained capsules, various physicochemical tests were conducted to examine particle size, encapsulation efficiency, thermal and moisture stability, and powder morphology. The spray-dried (SD) and freeze-dried (FD) powders had an average particle size of 8.35 µm and 144.49 µm, respectively. The SD powders showed similar encapsulation efficiency (EE) for soybean lecithin and pea protein isolate with an average value of 95.69%. On the other hand, the FD powders had lower EE compared to SD powders, with an average of 58.01% for lecithin-containing powders and 83.93% for pea-protein-containing powders. However, the water content of FD powders (2.83%) was lower than that of SD powders (4.72%). The powders prepared at pH 3 showed better thermal stability. Morphological analysis showed spherical particles for SD powders and irregular shapes for FD powders. Nanoemulsions as well as dried powders showed interesting antimicrobial activities against Escherichia coli and Listeria innocua, confirming their potential use as natural preservatives in foods.

In this research, some microbiological and physicochemical properties of milk powder produced by freeze dryer and spray dryer were determined during the storage period. Firstly, milks were divided into two groups. First group was dryed with freeze dryer. Second group was dryed with spray dryer. Total aerobic mesophilic bacteria, mould-yeast, total coliform and fecal coliform, moisture, hunter colour determination, water activity, pH analyses were performed in 2., 4. and 6. days of storage at room temperatures. Water absorption index, water solubility index, protein and microscopy analysis was performed in 2.day, 6.day and 6.day of storage, respectively. Moisture, water activity, microbiological analysis, L value and water absorption index values of freeze dryed milk powders were found lower than spray dryed samples in all days of storage. Microbiological quality of freeze dryed milk powder is better. It was thaught that the milk powder produced by freeze drying may have a longer shelf life at room temperature.

This study evaluated the encapsulation of cherry laurel (Prunus laurocerasus) fruit extracts by spray drying and freeze-drying using gum arabic, maltodextrin, and their mixture. Powder yields ranged from 63.57% (MD165) to 98.33% (MD-L), with freeze-dried samples showing higher recovery. Encapsulation efficiencies varied between 23.89% and 83.82%, highest in gum arabic-coated powders. Moisture contents ranged from 2.85% to 7.55%, with water activity below 0.32 for all samples. The highest total phenolic content (469.14 mg GAE/100 g) and antioxidant capacity (514.39 mg TE/100 g) were observed in freeze-dried samples. Thirty-three volatile compounds were identified by GC-MS; alcohols and hydrocarbons were found at higher levels in freeze-dried samples, whereas ketones were primarily formed in spray-dried powders. PCA and heatmap analyses confirmed that drying method and coating material significantly affected volatile profiles. PCA score plots clearly separated freeze-dried and spray-dried groups, with PC1 and PC2 explaining over 60% of total variance. Heatmap clustering showed gum arabic improved retention of acetic acid and esters, while maltodextrin preserved aldehydes like benzaldehyde. SEM images revealed smooth, spherical particles in spray-dried samples and porous, fractured structures in freeze-dried powders. Overall, freeze-drying combined with gum arabic achieved the best retention of bioactive and volatile compounds, while spray drying with maltodextrin produced powders with good morphology and flowability. These results highlight how encapsulation method and wall material selection optimize the functional quality of cherry laurel powders for use in value-added functional food products.

The influence of milk flow rate and inlet drying air temperature on the physical, optical and thermal properties of laboratory spray-dried camel milk powders is investigated. The physical, thermal and optical properties of laboratory spray-dried camel milk powders at three inlet drying air temperatures (110, 120 and 130 °C) and two milk flow rates (166 and 248 cm3/h) were evaluated. These properties are fundamental to understanding the quality, stability, final application and portability of the milk powders. Following this, the results were compared to commercial milk powder (CMM). Specifically, we evaluated the influence of the inlet drying air temperatures and feed rates on the reconstitution properties, particle properties, bulk, colour and thermal properties. Using response surface methodology (RSM), the findings indicated that the inlet drying air temperatures significantly influenced moisture content, and the L* a* b* colour properties (p < 0.0001) of the powders. However, the bulk and reconstitution properties were significantly influenced by the milk flow rate (p < 0.0001). The thermograms of all the milk powders had three endothermic peaks and two shifts. The onset of the glass transition increased in temperature with decreasing moisture content of the powders varying from 37.49 to 44.21 °C. Scanning electron microscopy (SEM) images of the laboratory spray dried powders were hollow and collapsed compared with the commercial samples which were spherical and rough with small cracks, dents and pores. The results demonstrated that both the inlet drying air temperature and the milk flow rate influenced the thermal, optical and physical properties of laboratory spray-dried powders.

This study compared the quality of organic strawberry powders, obtained by convective drying (CD), freeze drying (FD) and spray drying (SD) methods. In the study, such analyses were performed: the content of vitamin C and polyphenols by liquid chromatography method, antioxidant activity using ABTS+• radicals, microstructure using a scanning microscope, sensory quality by profile method and the determination of the physicochemical properties. The FD powders were characterised by the highest content of vitamin C and polyphenols, obtained values were close to fresh strawberries after conversion to the dry matter content. The content of these ingredients in CD and SD powders was lower by 55%–80% for vitamin C, and 80% for the polyphenols content. Strawberry flavour was most beneficial for the FD powders, while smoothness and homogeneity of appearance were equally rated for the FD and SD powders. Strawberry powders are a concentrate source of bioactive compounds and, therefore, the FD powders should especially be mainly used as a valuable component of high-value foods, especially functional foods, while CD and SD powders can be used to enrich food with vitamin C and as a valuable natural flavour and colouring component, replacing food additives.

Changes in the structure and composition of milk fat globules in spray- and freeze-dried milk powders have recently garnered notable attention. This study investigated changes in milk fat globular membrane (MFGM) proteins from bovine, goat, and horse milk powders, both spray- and freeze-dried, using a label-free proteomic approach, and quantified surface free fatty acids and their composition using GC. The results showed that several proteins, including αS2-CN and β-LG, increased, whereas fibrinogen α and β chain and mucin-1 decreased in the MFGM fractions of the studied spray-dried milk powders. Additionally, lactoperoxidase and polymeric immunoglobulin receptor levels were elevated in the studied freeze-dried milk powders. Several proteins exhibited variations in both dried milk powders depending on the species; of these, nucleobindin-1, complement C3, and sulfhydryl oxidase were increased in spray-dried bovine and goat milk powders, and lactoferrin was increased in freeze-dried horse milk powder, compared with their raw milk counterparts. Conversely, butyrophilin subfamily 1 member A1 and xanthine dehydrogenase/oxidase were decreased in spray-dried bovine and goat milk powders, S100 calcium-binding protein and aldehyde dehydrogenase were decreased in freeze-dried bovine and goat milk powders, and mucin-4 and paraoxonase were decreased in horse milk powder. Additionally, spray-dried milk powders had lower surface free fatty acid contents than freeze-dried milk powders. The findings underscore that drying methods exert varied effects on MFGM components of the studied milk sources, thereby providing a valuable reference for improving the nutritional quality of dried dairy products.