Changes in the flow properties of potato starch supplemented with super-fine eggshell powder

Abstract

Tons of eggshell waste contribute to the reduction in landfill capacity worldwide. This situation necessitates the development of diverse applications to expand their effective use. To develop new applications for eggshell, this study investigated the effects of eggshell powder on the flow properties of potato starch. Changes in the flow properties were evaluated by adding fine eggshell powder to potato starch at a concentration of 0.5–2.0 % (w/w). The angle of repose of potato starch without eggshell powder was 63 °. However, it decreased to 38 ° following the addition of eggshell powder at 2.0 % (w/w). In addition, eggshell powder positively affected the dynamic flow, bulk, and shear properties, indicating improvement in the flow properties of potato starch. Furthermore, eggshell powder changed the pasting properties of potato starch, with low and stable viscosities observed during heating. The findings demonstrate that the addition of eggshell powder improves the flow properties of potato starch. This could expand the applicability of this powder as an additive in food production.

Introduction

Eggs are a protein-rich food that is frequently consumed daily because of their high nutritional value. Egg production in 2020 reached 93 million tons, a significant increase from the 15 million tons produced in 1961ⁱ⁾. Asia is a major egg-producing region, with China being the largest producer in the world (Yang et al., 2018). This increase in egg production has been supported by an increase in global consumption, owing to changes in income and consumption habits (Waheed et al., 2020). Eggs are typically consumed directly as food, or industrially processed into other foods. However, the tons of eggshells are generated as byproducts are mainly disposed of as waste in landfills. However, since landfill capacity is limited (Ahmed et al., 2021), the effective use of eggshells is necessary in order to reduce waste and reduce environmental impacts.

Eggshells from industrial processes are used to modify the pH of acidic soils in the agricultural sector (Oliveira et al., 2013). In the food industry, they are used as a source of calcium supplementation because their main component is calcium carbonate (Murakami et al., 2007). This mineral is important for bone health, as calcium deficiency increases the risk of osteoporosis (Arnold et al., 2022). In the United States, it is estimated that osteoporosis of the femoral neck or lumbar spine affect 4.4 % and 19.6 % of males and females aged >50 years, respectivelyⁱⁱ⁾. Animal studies have shown that the calcium in eggshell powder is more digestible than that in purified CaCO₃, demonstrating that eggshells are well suited for use as a calcium supplement (Schaafsma and Beelen, 1999). Similarly, Sakai et al. (2017) showed that eggshell calcium results in a higher bone mass than calcium carbonate, making eggshells an attractive material for developing calcium-enriched foods. Previous studies have attempted to add eggshells to yogurt, muffins, and cookies for calcium fortification (Aditya et al., 2021; Shahnila et al., 2022). However, further development of diverse applications is required to expand their effective use.

This study examined the application of eggshell powder (EP) as an additive to improve the flow properties of food powders. Although the nutritional value, taste, and flavor are important elements of food powders, another key factor affecting food production includes flow properties. Powder flow properties are important in several processing stages, including storage, packaging, transportation, and manufacturing (Irie et al., 2021; Teunou et al., 1999). Thus, challenges can arise due to poor flow properties in these processes. The flow properties of powders depend on many factors, including particle size distribution, particle shape, moisture content, and interparticle cohesion (Ganesan et al., 2008; Fathollahi et al., 2020). Flow agents, such as silica, silicates, stearates, and phosphates, may be added to mediate insufficient flow properties (Onwulata et al., 1996). These flow agents can adhere to powder surfaces and act as lubricants to reduce friction between material particles (Chinwan and Castell-Perez, 2019). Thus, they are effective additives for avoiding production-line problems caused by powder flowability. Utilizing EP as a flow agent to improve flow properties could contribute to the development of new eggshell applications and a considerable reduction of the environmental impact of egg shells. To our knowledge, no reports have verified the changes in powder flow properties with the application of EP. Therefore, this study aimed to elucidate changes in the flow properties of potato starch (PS) after augmentation with EP, and to verify the applicability of EP as a flow agent.

Materials and Methods

Test materials　Commercially available EP (Calhope, Kewpie Egg Corporation, Tokyo, Japan) was finely ground and used as a flow agent. A 100 g sample of EP contains 38 g of calcium, 41.6 mg of potassium, 87 mg of sodium, 99.3 mg of phosphorus, 0.5 mg of iron, and 375 mg of magnesium (Kuroda and Kuno, 1999). Commercial food-grade PS (Kuroyanagi Seifun Co. Ltd., Aichi, Japan) was used for the flow property evaluation. The moisture contents of the EP and PS were 0.8 and 16.5 % w.b., respectively.

Milling conditions　A jet mill (IDS-2; Nippon Pneumatic Manufacturing Co., Ltd., Osaka, Japan) was used to reduce the EP size. Compressed air was injected into the equipment to enable high-speed airflow. The accelerated airflow reduced EP size upon impact with the collision plate, resulting in only fine particles being transported to the sample container. The particles were subsequently collected through a classifier that separated coarse and fine particles by airflow. The internal pressure of the nozzle was maintained at 0.6 MPa during milling.

Measurement of particle size distribution　Particle size was measured using a laser scattering diffraction particle size analyzer (LS 13 320, Beckman Coulter Inc., Brea, CA, USA) as described previously (Nei et al., 2022). A dry powder system module was used to obtain the 50 % cumulative volume (D50). To calculate the particle size, the refractive index of the sample was assumed to be 1.60.

EP addition and mixing　EP was added to PS at 0.5, 1.0, 1.5, and 2.0 % (w/w) (abbreviated as PS/EP0.5, PS/EP1.0, PS/EP1.5, and PS/EP2.0, respectively). The mixed powder was processed using stirring equipment (PM-1, AS ONE Corporation, Osaka, Japan) set to a rotational speed of 60 rpm for 1 h.

Scanning electron microscopy　The morphology of the PS powder was examined using a scanning electron microscope (JFC-1500; JEOL Ltd., Tokyo, Japan) at an acceleration voltage of 5 kV. Samples were sputter-coated with gold using a sputter coater (JFC-1500; JEOL Ltd., Tokyo, Japan) before imaging.

Measurement of aerated bulk density and angle of repose　The aerated bulk density and angle of repose were determined using a powder property tester (MT-1001; Seishin Enterprise Co., Ltd., Tokyo, Japan), as described previously (Nei et al., 2022), with slight modification. The samples were passed through a sieve with a mesh size of 355 µm and collected using a 100 mL container. Excess powder was removed from the top of the container, and the aerated bulk density was calculated. The PS was passed through a sieve with a mesh size of 355 um and spontaneously dropped onto the center of a circular table (diameter = 80 mm). Then, the angle of repose was measured as the angle of the cone formed by the deposited PS.

Evaluation of dynamic flow properties (stability and variable flow rate)　Flow properties of the powdered samples were measured using an FT4 powder rheometer (Freeman Technology, Ltd. Worcestershire, UK) with a 25-mm accessory kit. PS flow properties were evaluated using dynamic flow property (stability and variable flow rate tests), bulk property (compressibility and permeability tests), and shear cell tests. Moreover, the samples were analyzed using standard FT4 powder rheometer programs. Further descriptions of the instrument configuration and methods for analyzing the powder properties can be found in Freeman (2007) and Leturia et al. (2014).

Stability and variable flow rate test　The powder samples were transferred to volumetric vessels and pre-treated to remove excess particles before beginning measurements. Then, stability tests were conducted to measure the torque and axial force required for the blade to move through a powder layer. The blades were subsequently moved downward and upward through the powder bed, and the total energy was measured using analysis software. This process was repeated for seven cycles (Tests 1–7), with the blade travel speed set at 100 mm/s. Next, the basic flow energy (BFE), stability index (SI), and specific energy (SE) were determined. The BFE corresponded to the fluidization energy recorded in Test 7 of the seven-cycle repetition. SE was calculated based on the mass of the powder and the energy detected when the blade moved upward. The SE indicates powder flowability under unconstrained or low-stress conditions (Leturia et al., 2014). The SI was obtained from the ratio of the total energy detected at the first and seventh cycles of a seven-cycle repetition, as follows:

  

This indicator was used to assess the variability of the powders after fluidization (Leturia et al., 2014). Following the stability test, a variable flow rate test was conducted as described previously (Freeman, 2007). The sensitivity of the powders to changes in the flow rate was evaluated by decreasing the blade travel speed to 100 (Test 8), 70 (Test 9), 40 (Test 10), and 10 (Test 11) mm/s. The parameter obtained from the variable flow rate test was the flow rate index (FRI), which was determined using the ratio of the flow rate energy at 100 and 10 mm/s, as follows:

  

Bulk property test　Bulk property tests were used to evaluate the compressibility and permeability of the powder samples. This test is typically used to identify the changes that occur under normal stress in powder packing. Here, the samples were placed in a vessel and conditioned by moving the rotating blade downward and upward in the powder bed. The conditioning was performed three times. Next, the rotating blade was changed to a 23.5 mm vent piston after removal of excess powder from the vessel. The vent piston was then moved at a rate of 0.05 mm s⁻¹, and the volume change of the powder bed was measured while applying a normal stress of 1–15 kPa. The compressibility of the powders was compared by plotting the applied normal stress against the rate of volume change. In the permeability test, the rotating blade was changed to a 23.5 mm vent piston after three cycles of conditioning and removal of excess powder. Air was introduced at 2 mm s⁻¹, normal stress in the range of 1–15 kPa was applied to the powder bed, and the pressure drop was measured. Finally, the relationship between the applied normal stress and pressure drop was plotted to evaluate permeability.

Shear property test　 A shear test was performed to investigate the behavior of the powders as they changed from a static compacted state to a flow state. The 24-mm rotating shear cell accessory provided with the FT4 powder rheometer was used for this test. Powder samples were initially conditioned to a homogeneous and reproducible state using a rotating blade. Next, the powder samples were pre-compressed using a vent piston with a normal stress of 9 kPa. The vent piston was replaced with a shear cell head, and the powder sample was recompressed and pre-sheared at 9 kPa to achieve critical consolidation. Normal stress was decreased in increments of 1 kPa over a range of 7–3 kPa, and the shear stress required to fracture the consolidated powder bed was recorded. A normal-versus-shear stress diagram (yield locus) was obtained from the shear test results. Then, the cohesive strength and flowability index of the powder samples were determined based on the yield locus. The cohesion strength was obtained from the intercept of the linear regression of the shear stress versus the normal stress line at zero normal stress. The flowability index ff (–) is defined as the ratio of the major principal stress to the unconfined yield stress. Moreover, a higher ff value indicates better flowability of the powder.

Pasting properties　 Pasting properties were analyzed to elucidate the changes that occurred in the quality of PS when EP was added to improve the flow properties. Pasting properties were evaluated using a Rapid Visco Analyzer (RVA-4; Newport Scientific Pty. Ltd., Warriewood, NSW, Australia), as described previously (Noda et al., 2004). PS was added to distilled water to obtain a 4 % (w/w) suspension. The suspension was stored at 50 °C for 1 min, heated to 95 °C at a rate of 12.2 °C/min, and then stored for an additional 2.5 min. The suspension was then cooled to 50 °C at 11.8 °C/min and stored for 2 min. Finally, the viscosity value was recorded.

Statistical analysis　The R package (version 4.1.2; R Foundation for Statistical Computing, Vienna, Austria) was used for statistical analyses of the experimental data. All experiments were conducted in triplicate, and significant differences were determined using Tukey’s test. P < 0.05 was considered to be statistically significant.

Results and Discussion

Particle sizes and aerated bulk density of PS and EP　The particle size distribution of the PS and EP used in the tests is shown in Fig. 1. The particle size distributions of PS and EP had a single peak and had a shape that was similar to that of a normal distribution. The D₅₀ of PS and EP were 33 and 5 |im, respectively. The aerated bulk densities of PS and EP were 0.490 ± 0.005 and 0.619 ± 0.004 g/cm³, respectively (data not shown).

Fig. 1

Particle size distribution of potato starch (PS) and eggshell powder (EP). The solid and dashed lines represent the particle size of PS and EP, respectively.

Effects of EP addition on the PS angle of repose　The angles of repose of the powder samples are shown in Fig. 2. The angle of repose of PS without EP was 63°. The addition of EP to PS resulted in a significant decrease in the angle of repose (p < 0.05). The angle of repose is a measure of powder flowability that reflects the interaction forces between powder particles (Shen et al., 2022). A smaller angle of repose results in less friction between the particles and better powder flowability, suggesting that the addition of EP improves flow properties. The decrease in the angle of repose became more pronounced as the EP amount increased, with a decrease to 38 ° observed at 2.0 % (w/w). The addition of EP mitigated PS agglomeration, as shown in Fig. 3. Several large irregularly shaped clumps were observed in PS. However, the addition of EP resulted in a homogeneous powder without clumps.

Fig. 2

Changes in the PS angle of repose following the addition of EP. Data are expressed as the means of triplicate experiments. Error bars represent standard deviation, and different letters indicate significant differences (p < 0.05).

Fig. 3

Appearance of PS supplemented with EP. The EP concentrations are 0.0 (A), 0.5 (B), 1.0 (C), 1.5 (D), and 2.0 (E) % (w/w).

EP is believed to mitigate PS agglomeration, resulting in a lower angle of repose. Cohesive forces between powders are caused by van der Waals, electrostatic, and magnetic forces, as well as liquid cross-linking and interlocking. In addition, van der Waals forces are dominant in dry powders (Tomas and Kleinschmidt, 2009) and are affected by the distance between particles. SEM images of PS mixed with EP are shown in Fig. 4. As reported by Wang et al. (2016), the PS was composed of large ellipsoidal particles and small spherical particles. In general, as the contact area between particles increases, the van der Waals forces become stronger and flowability decreases (Kuakpetoon et al., 2001). Wang et al. (2016) investigated the flowability of PS with different particle sizes and reported that ellipsoidal PS with larger particle sizes has lower flowability than spherical PS with smaller particle sizes because of the larger contact area between particles. The EP adhered to the PS surfaces, and the adhered areas tended to increase with higher EP concentration. Bist et al. (2023) showed that buckwheat starch modified by octenyl succinic anhydride (OSA) esterification resulted in an irregular surface shapes and reduced cohesion between particles. In the present study, the adhered EPs made the surface structure of the PS particles irregular, and the PS cohesion was mitigated as a result of the reduced contact area between the particles. In order to effectively improve flow properties, it is important to mix EP and PS uniformly. As reported by Tran et al. (2019), the mixing conditions of additives have a significant impact on flow properties, and optimization will be a future task for more effective use of EP.

Fig. 4

Scanning electron microscope images of PS (A) and PS with EP added at 0.5 (B), 1.0 (C), 1.5 (D), and 2.0 % (w/w) (E).

Dynamic flow properties of potato starches　Results of the stability and variable flow rate tests are shown in Fig. 5. The total energy detected was represented by a rotating blade speed of 100 mm/s until the seventh test, followed by a decrease in the speed for the subsequent four tests. The parameters obtained from this test are shown in Fig. 6. Total energy increased with the addition of EP (Fig. 5). The BFE values changed with the addition of EP, with higher BFE values (p < 0.05) obtained with 0.5 % (w/w) EP compared to PS alone (Fig. 6). However, BFE values started decreasing when the EP concentration was increased from 0.5 % (w/w). Powders with low BFE values generally exhibit good flowability, whereas those with high BFE values often exhibit poor flowability. However, poor packaging and high porosity leads to contact between the rotating blades and a low-density particle bed with little interparticle contact, resulting in a low BFE (Scicolone et al., 2016). As PS contains many irregularly shaped clumps and is highly cohesive, it is possible that only a portion of the powder flows around the rotating blades, resulting in low BFE detection. In such cases, it may be easier to use SE values to evaluate flow properties (Nei, 2023). The SE value of PS was 6.8 mJ/g, and there was no significant difference in the SE values when EP was added at 0.5 % (w/w) (Fig. 6). However, the addition of EP at ≥ 1.0 % (w/w) significantly decreased SE values (p < 0.05). When EP was added at concentrations of up to 2.0 % (w/w), the SE value decreased substantially as the amount of the EP added increased. At additions of ≥ 1.5 % (w/w) EP, the SE values were < 5 mJ/g, indicating that SE values in this range are typical of “free-flowing” powder in low-stress environments (Leaper et al., 2018), markedly improving handling.

Fig. 5

Energy consumption in the dynamic flow of PS supplemented with various concentrations of EP.

Fig. 6

Parameters obtained from stability and variable flow rate tests. Data are expressed as the means of triplicate experiments. Error bars represent the standard deviation, and different letters indicate significant differences (p < 0.05).

Up to Test 7, the variation in the total energy with cycle repetition was low at a constant blade speed of 100 mm/s (Fig. 5). This was reflected in the SI value, which was expressed as the ratio of the total energy detected in Tests 1 and 7 (Fig. 6). SI values ranged from 1.1 to 1.3, with no significant difference in SI values observed with or without EP addition (p > 0.05). These findings indicate that the degrees of segregation, degradation, and agglomeration during repeated test cycles are not affected by EP addition.

The total energy increased when the blade rotation speed was reduced in Tests 8–11. Air in the powder bed can easily escape at low flow rates, resulting in high stiffness and flow resistance (Freeman, 2007), and thus, detection of higher energy. Furthermore, cohesive powders are generally sensitive to changes in flow rate, whereas the sensitivity to flow rates is considerably lower than their non-cohesive counterparts (Leturia et al. 2014). In the present study, the addition of EP slightly lowered the FRI values compared with the FRI, a measure of sensitivity to varying flow rates. This suggests that mixing EP with PS improved flowability based on the FRI index.

Bulk properties of potato starches　The compressibility test results of the powder samples are shown in Fig. 7a. Compressibility increased with higher normal stress, with and without the addition of EP. The highest compressibility was observed for PS, whereas PS with added EP (PS/EP0.5, PS/EP1.0, PS/EP1.5, and PS/EP2.0) showed reduced compressibility compared to PS alone. The PS compressibility was 17 % when a normal stress of 15 kPa was applied. Conversely, the addition of EP reduced the compressibility to 11.0–12.1 %. Although the compressibility of a powder is not a parameter directly related to flowability, it can be used to determine whether a powder is cohesive (Jan et al., 2017). Thus, highly compressible powders can be regarded as being highly cohesive. Here, the highly cohesive properties of PS were considered to have led to its higher compressibility, owing to the rearrangement of the particles upon the application of normal stress (Jan et al., 2017). As the addition of EP improved flowability, it was hypothesized that the powder was more optimally arranged when the container was filled with the powder. Thus, the particles were less likely to rearrange themselves when normal stress was applied, resulting in decreased compressibility. The pressure decreases under various normal stresses at an air flow rate of 2 mm s⁻¹ across the powder bed are shown in Fig. 7b. Powders with a small pressure drop exhibit high air permeability. The pressure drop increased with increasing normal stress. The increased normal stress could have reduced the distance between the particles, resulting in smaller air pathways (Barretto et al., 2022). The addition of EP affected the pressure drop, with PS having the lowest pressure drop. However, the pressure drop increased as the EP concentration increased. The PS structure contained several irregular clumps, which may have left relatively large air paths when normal stress was applied, resulting in a lower pressure drop. Alternatively, the pressure drop could have increased because the added fine EP blocked the air path when normal stress was applied. However, further investigation is required to determine the exact cause of the observed pressure drop.

Fig. 7

Compressibility (a) and pressure drop (b) of PS supplemented with various concentrations of EP. Data are expressed as the means and standard deviations from triplicate experiments.

Shear properties of potato starches　The parameters obtained from the shear-property tests are shown in Fig. 8. PS had a cohesion strength of 0.9 kPa. Compared to the cohesion of other products, the cohesion strength was reported to be 1.3 kPa for rice flour (Jan et al., 2017), suggesting that PS is less cohesive than rice flour. The addition of EP further reduced the cohesive strength (p < 0.05). The cohesive strength decreased significantly as the amount of ES added increased, and when the amount of EP addition was 2.0 % (w/w), the cohesive strength decreased to 0.3 kPa. This corresponds to one-third of the cohesive strength of PS without ES addition. Cohesion represents the shear stress required to fluidize a powder bed in an unconstrained state (Waiss et al., 2020). Moreover, the addition of EP can fluidize a powder bed at a lower shear stress. In this study, the addition of EP reduced the angle of repose and compressibility (Fig. 2 and 7). This is consistent with the results obtained by Marchetti and Hulme-Smith (2021), who stated that cohesive strength is strongly correlated with the angle of repose and compressibility.

Fig. 8

Cohesion and flowability index (ff) of PS supplemented with various concentrations of EP. Data are expressed as the means of triplicate experiments. Error bars represent the standard deviation, and different letters indicate significant differences (p < 0.05).

The ff value of PS was 5.1, which was the lowest value recorded. Although no significant difference was observed (p > 0.05), the addition of 0.5 % (w/w) and 1.0 % (w/w) EP increased ff values to 6.8 and 9.0, respectively. The ff values of PS/EP1.5 and PS/EP2.0 were significantly higher than those of PS alone (p < 0.05), indicating improved flowability. The ff value of PS/EP1.5 and PS/EP2.0 exceeded 10, which is defined as “free flowing”, according to Jenike’s (1964) classification. This further indicates that super-fine EP can be used to modify PS with excellent flow properties.

Pasting properties of potato starches　The RVA profiles demonstrating the pasting properties of the powder samples are shown in Fig. 9. The peak viscosities obtained from the RVA profiles are shown in Fig. 10. A distinct peak was observed in the analysis of PS paste, whereas the shape of the peak was more gradual in the EP-supplemented condition (PS/EP0.5, PS/EP1.0, PS/EP1.5, and PS/EP2.0). Peak viscosities were significantly lower (p < 0.05) for the samples with added EP than for those with PS alone. Furthermore, peak viscosities decreased with increasing EP concentrations. The peak viscosity of PS was 2 766 mPaꞏs, whereas that of PS/EP2.0 was 842 mPaꞏs. Rong et al. (2022) found no differences between the pasting properties of solutions with 8 % and 0.1 % (w/v) pea starch and EP and those without EP. However, the peak viscosity of a PS and Mesona chinensis Benth polysaccharide mixture decreased when EP concentration reached 0.4 % (w/v), indicating that the peak viscosity of the starch solution may be suppressed at a certain EP concentration threshold. Although the cause of this result remains unclear, one possibility is that the hydrophobic EP covers the surface of PS, subsequently preventing starch grains from absorbing water and swelling. Another possible cause might be a slight decrease in starch content per unit weight due to the addition of EP. In addition, it is also possible that the interaction of calcium with the phosphate groups of PS changed the viscosity properties. Noda et al. (2014) prepared calcium-fortified PS by soaking in CaCl₂ solution and determined viscosity properties and reported decreases in peak viscosity. PS viscosity peaked and then decreased sharply, owing to the collapse of swollen starch (Noda et al., 2004). However, the addition of EP lowered the peak viscosity and maintained a stable viscosity during high-temperature heating. This indicates small viscosity changes during heating and cooking, which could be advantageous depending on the application. On the other hand, a decrease in viscosity would affect thickening during cooking, and further studies on the treatment methods that minimize changes in viscosity properties may be required.

Fig. 9

Pasting behavior of PS supplemented with various concentrations of EP.

Fig. 10

Pasting property (peak viscosity) of PS supplemented with various concentrations of EP. Data are expressed as the means of triplicate experiments. Error bars represent the standard deviation from triplicate experiments, and different letters indicate significant differences (p < 0.05).

Conclusion

Eggshells are a by-product of largescale egg utilization in the food industry. As large quantities of eggshells are currently wasted, developing effective ways to use them would be environmentally and economically advantageous. This study attempted to improve the flow properties of PS by adding fine EP. The findings showed that EP decreased the angle of repose and improved the flow properties of PS. Further, EP also modified the pasting properties of PS, indicating that EP has the potential to markedly improve PS handling characteristics. These findings could contribute substantially to the expanded utilization of this powder as an additive agent for calcium supplementation in food production. However, the changes in viscosity characteristics depending on the processing and cooking application warrant further consideration. Changes in viscosity properties may be reduced by lowering the amount of EP added. Therefore, further investigation is required to improve EP preparation (optimizing particle sizes and/or shapes) for the subsequent improvement of flow properties at lower concentrations.

Acknowledgements　This study was supported by the Kieikai Research Foundation.

Conflict of interest　There are no conflicts of interest to declare.

References

•  Aditya,  S.,  Stephen,  J., and  Radhakrishnan,  M. (2021). Utilization of eggshell waste in calcium-fortified foods and other industrial applications: A review. Trends Food Sci. Technol, 115, 422–432. doi: 10.1016/j.tifs.2021.06.047
•  Ahmed,  T. A. E.,  Wu,  L.,  Younes,  M., and  Hincke,  M. (2021). Biotechnological applications of eggshell: Recent advances. Front. Bioeng. Biotechnol., 9, 675364. doi: 10.3389/fbioe.2021.675364
•  Arnold,  M.,  Rajagukguk,  Y. V.,  Sidor,  A.,  Kulczynski,  B.,  Brzozowska,  A.,  Suliburska,  J.,  Wawrzyniak,  N., and  Gramza-Michalowska,  A. (2022). Innovative application of chicken eggshell calcium to improve the functional value of gingerbread. Int. J. Environ. Res. Public Health, 19(7), 4195. doi: 10.3390/ijerph19074195
•  Barretto,  R.,  Buenavista,  R. M.,  Pandiselvam,  R., and  Siliveru,  K. (2022). Influence of milling methods on the flow properties of ivory teff flour. J. Texture Stud., 53, 820–833. doi: 10.1111/jtxs.12630
•  Bist,  Y.,  Kumar,  Y., and  Saxena,  D. C. (2023). Studies on rheological behavior of native and octenyl succinic anhydride modified buckwheat (Fagopyrum esculentum) starch gel and improved flow properties thereof. J. Food Process Eng., 46, e14193. doi: 10.1111/jfpe.14193
•  Chinwan,  D. and  Castell-Perez,  M. E. (2019). Effect of conditioner and moisture content on flowability of yellow cornmeal. Food Sci. Nutr., 7(10), 3261–3272. doi: 10.1002/fsn3.1184
•  Fathollahi,  S.,  Faulhammer,  E.,  Glasser,  B. J., and  Khinast,  J. G. (2020). Impact of powder composition on processing-relevant properties of pharmaceutical materials: An experimental study. Adv. Powder Technol., 31(7), 2991–3003. doi: 10.1016/j.apt.2020.05.027
•  Freeman,  R. (2007). Measuring the flow properties of consolidated, conditioned and aerated powders - A comparative study using a powder rheometer and a rotational shear cell. Powder Technol., 174(1–2), 25–33. doi: 10.1016/j.powtec.2006.10.016
•  Ganesan,  V.,  Rosentrater,  K. A., and  Muthukurnarappan,  K. (2008). Flowability and handling characteristics of bulk solids and powders - a review with implications for DDGS. Biosyst. Eng., 101(4), 425–135. doi: 10.1016/j.biosystemseng.2008.09.008
•  Irie,  K. R.,  Petit,  J.,  Gnagne,  E. H.,  Kouadio,  O. K.,  Gaiani,  C.,  Scher,  J., and  Amani,  G. N. (2021). Effect of particle size on flow behaviour and physical properties of semi-ripe plantain (AAB Musaspp) powders. Int. J. Food Sci. Technol, 56(1), 205–214. doi: 10.1111/ijfs.14620
•  Jan,  S.,  Ghoroi,  C., and  Saxena,  D. C. (2017). Effect of particle size, shape and surface roughness on bulk and shear properties of rice flour. J. Cereal Sci., 76, 215–221. doi: 10.1016/j.jcs.2017.04.015
•  Jenike,  A. W. (1964). Storage and flow of solids, Bulletin of the University of Utah, 123.
•  Kuakpetoon,  D.,  Flores,  R. A., and  Milliken,  G. A. (2001). Dry mixing of wheat flours: Effect of particle properties and blending ratio. LWT, 34(3), 183–193. doi: 10.1006/fstl.2001.0756
•  Kuroda,  N. and  Kuno,  N. (1999). Uses of Call-Hope, eggshell powder, for food. part 2. Application of eggshell calcium for food. A Technical Journal of Food Chemistry & Chemicals, 15(8), 101–105.
•  Leaper,  M. C.,  Ali,  K., and  Ingham,  A. J. (2018). Comparing the dynamic flow properties and compaction properties of pharmaceutical powder mixtures. Chem. Eng. Technol., 41(1), 102–107. doi: 10.1002/ceat.201600651
•  Leturia,  M.,  Benali,  M.,  Lagarde,  S.,  Ronga,  I., and  Saleh,  K. (2014). Characterization of flow properties of cohesive powders: A comparative study of traditional and new testing methods. Powder Technol., 253, 406–423. doi: 10.1016/j.powtec.2013.11.045
•  Marchetti,  L. and  Hulme-Smith,  C. (2021). Flowability of steel and tool steel powders: A comparison between testing methods. Powder Technol., 384, 402–413. doi: 10.1016/j.powtec.2021.01.074
•  Murakami,  F. S.,  Rodrigues,  P. O.,  de Campos,  C. M. T., and  Silva,  M. A. S. (2007). Physicochemical study of CaCO₃ from egg shells. Ciênc. Tecnol. Aliment., Campinas, 27(3), 658–662. doi: 10.1590/S0101-20612007000300035
•  Nei,  D. (2023). Effect of milling method on shape characteristics and flow, bulk, and shear properties of defatted soybean flours. J. Food Meas. Charact., 17(2), 1823–1830. doi: 10.1007/s11694-022-01755-x
•  Nei,  D.,  Ando,  Y., and  Sotome,  I. (2022). Effect of blanching periods and milling conditions on physical properties of potato powders and applicability to extrusion-based 3D food printing. Food Sci. Technol. Res., 28(3), 207–216. doi: 10.3136/fstr.FSTR-D-21-00283
•  Noda,  T.,  Tsuda,  S.,  Mori,  M.,  Takigawa,  S.,  Matsuura-Endo,  C.,  Salto,  K.,  Mangalika,  W. H. A.,  Hanaoka,  A.,  Suzuki,  Y., and  Yamauchi,  H. (2004). The effect of harvest dates on the starch properties of various potato cultivars. Food Chem., 86(1), 119–125. doi: 10.1016/j.foodchem.2003.09.035
•  Noda,  T.,  Takigawa,  S.,  Matsuura-Endo,  C.,  Ishiguro,  K.,  Nagasawa,  K., and  Jinno,  M. (2014). Preparation of calcium- and magnesium-fortified potato starches with altered pasting properties. Molecules, 19, 14556–14556. doi:10.3390/molecules190914556
•  Oliveira,  D. A.,  Benelli,  P., and  Amante,  E. R. (2013). A literature review on adding value to solid residues: egg shells. J. Clean. Prod., 46, 42–47. doi: 10.1016/j.jclepro.2012.09.045
•  Onwulata,  C. I.,  Konstance,  R. P., and  Holsinger,  V. H. (1996). Flow properties of encapsulated milkfat powders as affected by flow agent. J. Food Sci., 61(6), 1211–1215. doi: 10.1111/j.1365-2621.1996.tb10962.x
•  Rong,  L. Y.,  Shen,  M. Y.,  Wen,  H. L.,  Xiao,  W. H.,  Li,  J. W., and  Xie,  J. H. (2022). Eggshell powder improves the gel properties and microstructure of pea starch-Mesona chinensis Benth polysaccharide gels. Food Hydrocoll., 125, 107375. doi: 10.1016/j.foodhyd.2021.107375
•  Sakai,  S.,  Hien,  V. T. T.,  Tuyen,  L. D.,  Duc,  H. A.,  Masuda,  Y., and  Yamamoto,  S. (2017). Effects of eggshell calcium supplementation on bone mass in postmenopausal Vietnamese women. J. Nutr. Sci. Vitaminol., 63(2), 120–124. doi: 10.3177/jnsv.63.120
•  Schaafsma,  A. and  Beelen,  G. M. (1999). Eggshell powder, a comparable or better source of calcium than purified calcium carbonate: piglet studies. J. Sci. Food Agric., 79(12), 1596–1600. doi: 10.1002/(SICI)1097-0010(199909)79:12<1596::AID-JSFA406>3.0.CO;2-A
•  Scicolone,  J. V.,  Metzger,  M.,  Koynov,  S.,  Anderson,  K.,  Takhistov,  P.,  Glasser,  B. J., and  Muzzio,  F. J. (2016). Effect of liquid addition on the bulk and flow properties of fine and coarse glass beads. AIChE J., 62(3), 648–658. doi: 10.1002/aic.15004
•  Shahnila,  Arif,  S.,  Pasha,  I.,  Iftikhar,  H.,  Mehak,  F., and  Sultana,  R. (2022). Effects of eggshell powder supplementation on nutritional and sensory attributes of biscuits. Czech J. Food Sci., 40(1), 26–32. doi: 10.17221/309/2020-CJFS
•  Shen,  C. P.,  Li,  Y. X., and  Xu,  X. M. (2022). Analysis of the compressibility of edible powders under low pressure. J. Food. Eng., 316, 110828. doi: 10.1016/j.jfoodeng.2021.110828
•  Teunou,  E.,  Fitzpatrick,  J. J., and  Synnott,  E. C. (1999). Characterisation of food powder flowability. J. Food Eng., 39(1), 31–37. doi: 10.1016/S0260-8774(98)00140-X
•  Tomas,  J. and  Kleinschmidt,  S. (2009). Improvement of flowability of fine cohesive powders by flow additives. Chem. Eng. Technol., 32(10), 1470–1483. doi: 10.1002/ceat.200900173
•  Tran,  D. T.,  Majerová,  D.,  Veselý,  M.,  Kulaviak,  L.,  Ruzicka,  M. C., and  Zámostný,  P. (2019). On the mechanism of colloidal silica action to improve flow properties of pharmaceutical excipients. Int. J. Pharm., 556, 383–394. doi: 10.1016/j.ijpharm.2018.11.066
•  Waheed,  M.,  Yousaf,  M.,  Shehzad,  A.,  Inam-Ur-Raheem,  M.,  Khan,  M. K. I.,  Khan,  M. R.,  Ahmad,  N.,  Abdullah, and  Aadil,  R. M. (2020). Channelling eggshell waste to valuable and utilizable products: A comprehensive review. Trends Food Sci. Technol., 106, 78–90. doi: 10.1016/j.tifs.2020.10.009
•  Waiss,  I. M.,  Kimbonguila,  A.,  Abdoul-Latif,  F. M.,  Nkeletela,  L. B.,  Matos,  L.,  Scher,  J., and  Petit,  J. (2020). Effect of milling and sieving processes on the physicochemical properties of okra seed powders. Int. J. Food Sci. Technol., 55(6), 2517–2530. doi: 10.1111/ijfs.14503
•  Wang,  C.,  Tang,  C.,  Fu,  X.,  Huang,  Q., and  Zhang,  B. (2016). Granular size of potato starch affects structural properties, octenylsuccinic anhydride modification and flowability. Food Chem., 212, 453–459. doi: 10.1016/j.foodchem.2016.06.006
•  Yang,  Z.,  Rose,  S. P.,  Yang,  H. M.,  Pirgozliev,  V., and  Wang,  Z. Y. (2018). Egg production in China. World’s Poult. Sci. J., 74(3), 417–426. doi: 10.1017/S0043933918000429
• i)  https://www.fao.org/faostat/en/#data/QCL (Oct. 10, 2023)
• ii)  https://www.cdc.gov/nchs/products/databriefs/db405.htm (Oct. 10, 2023)