Spray dryer is another option. But I have a freeze dryer with me. So can this existing freeze dryer be used for drying of herbal extracts instead of purchasing another spray dryer for the same purpose? The utmost concern is the effect of freeze drying on the extracts. What effects it would pose on the extracts? Is spray drying better or the existing freeze dryer can be used?
Hi. I am not sure what is the nature of your herbal extract, but I have done some trials of drying fresh dragon fruit using freeze dryer and oven. The product of freeze dryer retains the fresh red colour of the fruit, but the product dried in oven is dark and dull. From the findings, I believe that freeze drying does not pose harsh drying condition on the substrate. Besides, freeze drying has also been used to dry fresh mushroom samples for extraction of mushroom extracts in our school.
Yes you can use freeze drying. This will be good because in spray drying some degradation may occur due to temperature but this is not with the freezedrying. I think you should go with freezedring if possible.
In addition, Freeze Dried extracts retain thermolabile compounds which you will loose in spray drying at higher temperature.
Yes. As said before, as freeze drying does not use high temperatures its a very good method to dry extracts without causing major changes on their properties.
We did not use spray drying but we have compared the loss in antioxidant capacity (based on 4 different assays) by sun drying, oven drying and air drying of 3 fruits including amla (Indian gooseberry). We found the freeze drying to retain maximum antioxidant capacity since it does not raise the temperature of the material leading to reduced chemical degradation of phyto-ingredients and also gives less exposure to air during drying. . .
You can use the free drier because it only removes the water while retaining your compounds of interest.
Freeze dryer is generally used for aqueous extracts. This type of drying will not harm the herbal extracts because i carry out through this process for drying up of my sample using freeze dryer and go for powdering of the sample.
Yes, as others have stated, you can use it to dry herbal extracts and the product retains much of its properties that are lost with spray drying, but from my experience, the best method also depends much on the amount of the extract to be dried. it is recommended for each vial to have a liquid depth of about 1-2 centimeters to ensure quick and homogeneous drying, and so it will take a VERY long time to dry large amounts of extracts, even with much more liquid depth in each vial.
Since freeze drying requires a lot of energy, and sometimes time, you may also try to simply vaccume dry the extract solutions at low, but not frozen temperatures. This will be much quicker and hopefully the rather low temperature in combination with vaccume will allow for drying without degradation (note that a cold trap such as present on a freezedryer is needed to avoid the vapour to go into the vaccume pump).
As all the others have noted, the relatively low temperatures involved in the sublimation should ensure that your compounds of interest are not affected. You should ensure that your extracts are thoroughly frozen beforehand and move quickly when transferring them to the drier
I use freeze drying extensively for plant and soil extracts. freeze drying will work great for leaf extracts and is a very non-invasive technique. please make sure the samples are frozen completely.
If you have an aqueous extract, freeze dry is a very useful option. And its also an easier procedure than spray dry.
yap freeze dryer can be used and as Mr Robin Joshi said it should be preferred upon spray drying as the natural products have the tendency to get degrade with heat and there can be loss essential elements.also it is correct that it will surely depend upon the qty of material to be freeze dried as large quantity can cause damage to freeze drier.adding to it the presence of solvent(or water ) should be kept extremely low.
Certainly! As others have indicated earlier, you can freeze-dry your aqueous herbal extracts. Just ensure that it is well frozen and forms a thing layer. Additionally, ensure that there is no organic solvent as part of the mixture.
For sure, as many others have said, you can freeze-dry aqueous herbal extracts. It is even one of the best procedure to get complete dryness.
However, there are 2 restrictions to use it :
1) if your primary extract required organic "cosolvent" such as methanol, ethanol, or acetone to be obtained from the plant powder, you must first to distill it off under vacuum (rotavapor, under 40°C). Otherwise, you cannot freeze the water phase completely and the sublimation step will not go smoothly ...
2) depending on the nature of your extract: for instance, with essential oils forget it ! Individual terpenoids constituents would be lost (too much volatile under the conditions)! But, most probably, it is not your case since water is rarely used to extract such metabolites.
Good work.
Ms. Vaishali Agte from Agharkar Research Institute has some good findings there about the advantage of using freeze dryer :-) Great work
I agree with many other people. Freeze drying is a great way to dry the samples. You might find that you get a few different products this way because there is less chance for degradation or rearrangement of some compounds. As Joseph V commented, you would likely loose some volatile components that could be collected by distillation.
I want to stress the need that the previous freezing step was completely done. Use -80ºC freezer, if available, or at least the cold trap of the lyophylizer to freeze samples below -40ºC before starting lyophylization. Also aliquot the bulk sample in small volumes to increase the performance of the process.
I feel the best options is freeze dryer if you are having aqueous extract. If you are having any organic solvent extracts - the best one is just air dry. ( if interested you can carry out with spray drying too)
Thanks all. Only query in my mind is that in cold conditions crystallization might take place in the extract. Is their anything like this? Also the amount of sample to be used for this purpose is creating confusion. Can we use higher amounts of extract, lets say, 500 gm at a time or it depends on the size of the instrument. What is the ideal amount that should be used for the purpose?
I believe it is possible as I have heard of other researchers using it. A definite use of it for drying down herbal extracts. If volatile solvents such as chloroform, methanol, ethyl acetate etc...
if you have aqueous extract in bulk and with low concentration of soluble solids (or volume is beyond the capacity of your freeze dryer unit) you can partially reduce the volume under vacuum below 40C followed by freeze-drying.
Yes of course, for aqueous extract and free volatile-extract.
Very well, just like others have confirmed. Its one of the best and efficient way to dry your aqueous plant extract provided all other organic solvents are first completely removed.
I agree with many other people. Freeze drying is a great way to dry the samples.
Mr Alok no need to worry about crystallization as the mechanism behind freeze dying is sublimation, amount of the extract depends upon the capacity of the machine
Hi.
I have already used a freeze dryer to dry my hexane, ethyl acetate, methanolic and aqueous extracts. Its a good way specially for hexane extracts to be well powdered.
Hello
I have some experience of freeze drying small molecules (not natural products). If you are worried about crystallisation then one must first characterise properties of API both with and without solvent which can include it’s freezing behaviour, drying , crystallisation. This will help you to understand what parameters to select for the freeze-drying process.
Thanks a lot to all of you for your valuable comments and suggestions.
Best Regards
I think it is a better approach than spray drying since the heat that you generated in spray drying may cause damages for the sensitive-heat compound in your extract. Spray drying also leaves some extract "debris" in the glass tube, that is sometimes hard to collect. Do others share my views? Any comment would be gratefully accepted.
I think Freeze dryer is good option but may be not suitable for some extracts because all the extracts has a different characteristic .
In my experience freeze driers do pretty well for aqueous extracts, that is after freezing normally overnight. on the other hand organic solvent extracts may not be so suitable as certain solvent do not easily freeze to solid therefore sublimation as the main process during freezing drying not occurring
Dr. I have used freeze drier for my Methanol extracts. It worked. But still my extracts looks oily (not completely powdered). I think it depends of presence of type of compounds and may vary from species to species.
Freeze drying is only for aqueous extract....Extract in organic solvents can't be freeze dried (also does not require).
Dr., Freeze drying can be used in case of aqueous extract and samples should be of small volumes. before using the instrument you must be sure that your sample is well frozen
Yes we can use a freeze dryer for drying of herbal extracts instead of a spray dryer and comparatively it is better.
Freeze dryer is better than spray dryer as in spray dryer heating is there which may degrade the compounds.
Sir, freeze drying is a preferred option to spray drying as it will aid in preserving the inherent features of the herbal extracts as well as aid in giving reproducible yield over time.
In general, yes you can, sometimes depend on the nature of your extract
Freeze drier is only for aqueous extract. Solvents extract can damage the machine especially pump and rubber.
You can use liquid Nitrogen to freeze and then overnight vacuum in freeze dryer.
The choice of dryer depends on the type of material that needs to be dried.
Spray drying, owing to high temperatures can sometimes degrade the quality of your product.
In case of freeze drying, the nature of your extract plays an important role since it can take a long time to reach eutectic point (during freezing cycle) if it contains constituents other than water. This problem is more evident only when you set a lyophilization program with all the freezing and drying cycles. In such a case you can manually freeze the sample under liquid nitrogen followed by drying. Otherwise you can first remove the solvent (say alcohol) under vacuum followed by reconstitution with water. The obtained can be easily freeze dried.
Manas Boxi explained in detail as I suggested earlier. I hope you got a lot of answers and you are clear now.
It depends on your compounds in extracts, for example carotenoids are degradated after lyophilization. Not many papers show problem with bioactive compounds degradation of lyophilized plant materials.
It depends to your freeze dryer temperature. Please check the spec of your machine. Normally it is either -55, -95 or -100 deg Celcius. If your solvent is frozen at that temp than you can use this technique. If not, than you can't use. Manas Boxi has explained the technique to make sure the sample is frozen when introduced into the freeze dryer. You can use cosolvent to adjust the freezing temp of your sample as well. Hope this helps.
you can dry your extract in freeze dryer, but before that you have to look into the amount of solvent which is present in your extract. If it is less in amount then keep it in ultra low freezer at -80oC. , then under completely frozen condition immediately u have to place it inside the lyophilizer. Then no problem at all. After completion of freeze drying the residual solvent u can remove by keeping it inside a vacuum dessicator.
What kind of solvent was employed to get the extract? In case of water I should use the freeze dryer, it a gentle way to take out water. The key point is to get the sample realy frozen. If the extract contains water or another orgnic solvet, it must be removed before trying to freeze the sample. Water plant extract runs very well at 20 °C, at 80 -100 mTorr. One of the problems with the freez drying process is the time it takes and the cost of the equipment. Freeze dryed extracts are highly hygroscopic!
I will consider freeze dry if I were to choose in between the two...depends on ur availability of freeze dryer
If you are dealing with a decoction, then freeze drying is the best option. With the use of a chiller unit you can then freeze your extract as you rotate it in order to obtain a frozen layer inside your pear-shaped flask, this increase the surface area for drying faster. Then attach it to your freeze dryer.
Freeze drying is best for drying heat labile material, but it is slow process as you compare with spray drying.
I agree with Tapaswi Dash, conditionally the extract contains water contents
Does anyone know a good protocol for freeze-drying aqueous herbal extracts? I have read numerous paper that conducted studies with freeze-dried herbal extract, but they dont give much detail about the freeze-drying process.
I always prefers shaking water-bath for drying the extract at 38 degree centigrade. I thing is one of the best methods for drying...........
Freeze drying will be the best for drying heat labile material (drying the sample to remove water from it). If herbal extract consisting of alcohol, acetone, DCM etc, first of all you may use shaking water-bath or rotary vacuum evaporator (temp. less than 40) to remove these organic solvents and finally you can use freeze dryer to remove water from your herbal extracts. It will be the best way to dry your sample.
Freeze drier is better if you want to dry aqueous extracts. What you are required to do is to freeze your extracts by keeping them at -20 degree or use other means to freeze and then take them to the freeze drier. If your extract is extracted using organic solvent make sure that all organic solvents are removed first by vacuum rotary evaporator or other means before taking it to the freeze drier. Note that don't put liquid extracts in the freeze drier as it will be sacked out of the container by the vacuum within the freeze drier. You can divide your extract(s) into small amounts so that to increase the efficiency during drying.
Yes, Freeze drying will be the best for drying aqueous extracts. You must follow the procedure that described by Ramadhani Nondo
Yes, but for only extract containing other then oil and related substances.
Yes you can and probably can get better results however cost wise it is not very favourable.
Lyophilisation dose not helps the organic soluble substances. It has the limitation
Organic soluble substances can easily be dried by using vacuum rotary evaporator. So why do you use freeze drying system?
If you have a freeze dryer already it is the best option. Freeze drying will also remove organic solvents but if you too much solvent you will reduce the pump oil life and may need to change it more frequently - only if using solvents in excessive amounts for extended periods.
Lyophilization is the process which capable of removing the water content from slurry. It may does not working to remove organic solvents which may cause the instrumental problem. in another way it so difficult to make an ice form from organic solvents, so we use water to ice in -80 degree Celsius.
A freeze dryier is better option. Normally, a freeze drier is used to dry substances which sensitive to high temperature. If you use a spray drier, some compounds in herbal extract will probably decompose at high temperature.
Freeze dryer is the best equipment to evaporate water content from thermolabile mixtures/ crude extracts.
i used my methanolic extracted sample in rotatory evaporator at 40 degree C and 70 mbar to remove methanol and water .And then i put it at refrigerator to freeze and then i put it in freeze drying for 24 hr . At final, my sample is so sticky to remove from container . how can i do it for that ? please let me know ur suggestion . thanks ....i want to use it for measuring antioxidant activity .
You can use very small amount of distilled methanol (100% methanol) to remove the sticky sample from container and pour the sample in a small beaker. Then dry the solvent by using water bath at 40 degree C for all day long and finally use vacuum desiccator to dry the sample.
Most important note is : you must consider that most of the lyophilizer machines only compatible with aqueous extract which means you can not use the lyophilizer for organic extract at all.
Also you must bear in mind that some ingredients in your plants is organic soluble not water soluble and vice versa so the same crude material you should have both extract water and organic and the process for gathering the final powder of each extract different, the aqueous by lyophilizer and the organic one by the rotary evaporator.
In freeze drying process you must solidify your product containing solvents by freezing them. Their elimination occures under vaccum and with increasing temperature.
Unfortunately, ethanol has a very low solidification temperature about -114 °. In order to freeze dry your product, you must freeze it into liquid nitrogen. After that you can sublimate it in a freeze dryer.
lyophilization is an excellent technique for drying moisture or heat sensitive drugs or herbal products. This is due to the evaporation of water or solvent at lower temperature. In addition, freezing stage in lyophilization can inhibit the action of microorganisms. Higher porous structure produced can lead to rapid wetting of these powders when prepared as sachets.
Lyophilization where the water molecules were separated from the mixture of aromatic oils and oils remains in the container
No not for all types of extract. the extract reach in Tannin content only can be dried but not others containing even traces of glycosides. Your extract will be sticky.
Yes you sure can do that, however you need to think about the cost as well.
Freeze drying or Lyophilization is a very efficient method generally used for drying aqueous extracts. Many of the organic solvents owing to their very low freezing temperature need to use suitable co-solvent while lyophilization. For removal of organic solvents rotavaporation is advisable. Drying with liquid nitrogen is another option for organic solvents. You have not mentioned about the solvent used for your extract. You can use Lyophilization to dry your extract. However, compatibility of solvent with the pump of Lyophilizer is the limitation with this method.
Aqueous solvent soluble substance can be easily separated by Freeze drying or Lyophilization process from the mixture oil-water emulsion.
Freeze dryer are best for freeze drying components eg like water.freeze drying is perform at low temparature.
Spray drying incorporates heat to the solution to dry so it can degrade heat sensitive drugs while freeze drying prevent it.
Freeze drying is applicable if your sample contain moisture instead of organic solvents in the herbal extracts. Organic solvents may destroy some of the parts of the machine, and it is not advisable to freeze dry the herbal extracts that are extracted through organic solvents. only temperature sensitive aqueous extracts should be processed through freeze drying equipment.
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