Liquid lactoferrin either from skim milk, cheese, or whey is converted into dry powder form to extend its shelf-life and preserve its functional properties.
Industrially, bovine lactoferrin (bLF) powders are produced using spray drying or freeze drying.
With the recent increase in the market demand for bLF powders, people start to look over the difference between the quality of powder produced from the two options to assess which will best fit their requirements and purposes.
Manufacturers usually receive these questions: Which has higher antioxidant capacity? Higher water solubility? Lower denaturation? More intact molecular configuration? Higher protein content? Higher moisture content?
However, manufacturers seem to provide conflicting responses.
To help shed light on the debate around the two drying technologies, let’s examine two known studies, to date, comparing the effects of both methods on the resultant powders.
Denaturation
Before we start, let’s define denaturation. Denaturation occurs when there is a partial or total alteration of the molecule’s native secondary, tertiary, and/or quaternary structures.
In the 2017 study by Wang et. al., results showed that spray-dried and freeze-dried lactoferrin powders had insignificant denaturation changes compared to the liquid bLF.
They used a laboratory scale spray dryer with outlet temperatures of 70 ◦C and 95 ◦C and a laboratory scale freeze dryer for this study.
Researchers suggested that the low temperature used in freeze drying and the fast-drying rate and the very short residence time during spray drying help preserve the native molecular configuration, not causing significant structural modification. Time of exposure and availability of water is considered more critical factors than the drying temperature in denaturing liquid bLF.
On the other hand, in the 2022 study by Morel et. al., researchers mimicked industrial production conditions. For spray drying, they used a larger spray drier and longer powder residence than the previously mentioned study. They also set a higher inlet temperature. Meanwhile, freeze-dryers were set to higher temperatures during the primary and secondary drying steps simulating “industrial practice.”
Results showed that spray-dried lactoferrin was more highly denatured than freeze-dried and liquid bLF. However, they also noted that the spray-dried powders produced were significantly drier, indicating a harsher thermal history.
Moisture Content, Water Activity, and Solubility
The 2017 study revealed that the solubility of the freeze-dried powder was lower than the spray-dried ones. Spray-dried powders and freeze-dried powder were amorphous with >98% and >94% solubility in water, respectively. Researchers said that it might be due to the larger particle size of the freeze-dried powder.
As for the residual moisture content and water activity, freeze-dried powders contained about half the spray-dried powder dried at 95 ◦C outlet temperature and a quarter of the spray-dried powder dried at 70 ◦C outlet temperature. This indicates that the spray drying conditions retained more water.
Centered on these results, researchers stressed that “a spray drying process with 180 °C inlet and 95 °C outlet temperature produce similar or better-quality powders compared to the ones produced through a freeze-drying process.”
However, the 2022 study reported that the spray-dried lactoferrin using larger driers, longer powder residence, and higher inlet temperature had lower moisture levels than the previous study. The moisture levels were above the ideal range for commercially produced lactoferrin. Unfortunately, the study did not test the moisture content of the freeze-dried powder.
Antioxidant Capacity
Researchers found that the antioxidant capacity of spray-dried lactoferrin powder was higher than that of freeze-dried powder (1). The antioxidant activity of spray dried powder was similar to that of the liquid bLF while it was ∼6% less in the freeze-dried powder.
They suggested that the decrease of antioxidant activity in freeze-dried powder could be attributed to its lower solubility which would reduce the chances of the interaction of lactoferrin and free radicals. They also attributed it to the reduction in ferric ion content by oxygen during the long drying process.
Antimicrobial Activity
It was confirmed that the drying method had no significant effect on the antimicrobial effects of lactoferrin. Researchers stressed that lactoferrin’s antimicrobial activities are linked to its ability to interact with the microbial cells’ surface, independent of its ability to bind with iron.
Protein Content
In the 2017 study, the protein content of both powders was higher than 90% with no significant difference. So, this indicates that both drying method is suitable for formulas needing protein in the bovine lactoferrin.
Iron-binding Properties
Denaturation of lactoferrin can cause a reduction in the iron binding capacity of the molecule. The higher extent of denaturation the higher the molar iron to lactoferrin ratios.
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|
2017 |
2022 |
||
|
Freeze-dried LF Powder |
Spray-dried LF powder |
Freeze-dried LF Powder |
Spray-dried LF powder |
|
|
Bulk Density |
Higher |
Lower |
-- |
-- |
|
Color |
Darker |
Lighter |
-- |
-- |
|
Water Activity |
Lower |
Higher |
-- |
-- |
|
Solubility |
Lower |
Higher |
-- |
-- |
|
Moisture Content |
Lower |
Higher |
-- |
-- |
|
Denaturation |
No significant difference |
No significant difference |
Lower |
Higher |
|
Antioxidant Capacity |
Lower |
Higher |
|
|
|
Antimicrobial Capacity |
-- |
-- |
No significant difference |
No significant difference |
|
Iron-binding Properties |
-- |
-- |
Higher |
Lower |
|
Protein Content |
No significant difference |
No significant difference |
|
|
Now that we’ve compared the effects of drying processes and conditions on the quality of lactoferrin powders, it is apparent that bovine lactoferrin manufacturers must be able to tailor-fit the drying methods. While the latter study highlighted its replication of industrial practice, it is important to note that, not all lactoferrin manufacturers are the same and some can customize production for the client’s needs like Lactoferrin.co.
Using both drying technologies, Lactoferrin.co prides on its expertise in producing tailor-fit lactoferrin powders for different purposes and requirements.
To consult, book a quick meeting with us now: https://calendly.com/lactoferrinco.
References:
Wang, B., Timilsena, Y. P., Blanch, E., & Adhikari, B. (2017). Characteristics of bovine lactoferrin powders produced through spray and freeze drying processes. International Journal of Biological Macromolecules, 95, 985–994. https://doi.org/10.1016/j.ijbiomac.2016.10.087
Morel, J., Md Zain, S. N., & Archer, R. (2022). Comparison of drying techniques for bovine lactoferrin: Iron binding and antimicrobial properties of dried lactoferrin. International Dairy Journal, 124, 105142. https://doi.org/10.1016/j.idairyj.2021.105142