Starch is a large carbohydrate polymer that plants use to store energy.
its found in all plants but the amount that they store varies, and the largest amounts can be found in things like potatoes, corn, wheat or rice.
The polymer of starch is made up of many glucose units, connected by something known as glycosidic bonds.
In starch the type of glycosidic bonding that occurs is almost completely alpha 1-4
where the alpha refers to the orientation of the bond
and the 1-4 refers to the specific glucose carbons that are involved in the bond.
Starch actually consists of two major components where one is called amylose and the other one is called amylopectin.
The amylose is entirely alpha 1-4 linked glucose units
but the amylopectin also has alpha 1-6 linked glucose units
the addition of these alpha 1-6 linked glucose units
gives it a little bit of branching and more bulk and alters its properties a little bit compared to amylose.
I just really wanted to quickly mention cellulose which is another plant glucose polymer
but instead of being connected by alpha 1-4 bonds, they are connected by beta 1-4 glycosidic bonds.
Humans and almost all animals have the enzymes to break the alpha 1-4 bonds of starch and liberate the glucose units
but we don't have the proper enzymes to break the beta 1-4 bonds of cellulose.
When we eat things that are high in starch like rice, potatoes, corn, etc.
we can break down the starch to glucose and use it for energy.
However just this difference in how the glucose is linked together
it makes it so that when we eat things which are high in cellulose like vegetables or fruits, most of it leaves our body undigested.
Anyway that's a little bit of a tangent and now i want to talk about why i even need potato starch.
And why i don't just use corn starch which can be easily purchased from the store.
The simple answer is that not all starch is the same, and there is a slight difference between corn starch, potato starch etc.
I dont want to go into too much detail but one major difference between potato starch and some of the other starches
is that its very low in protein and fat contaminants.
A lot of other starches like corn starch for example contain a lot of protein and fats
which give water starch solutions a slightly cloudy or opaque look.
In a previous video I covered the iodine clock reaction.
This is a reaction where two colourless solutions are mixed
and after a certain period of time a sudden colour change occurs.
One of the colourless solutions thats used contains starch
and at the time I only had corn starch so you can see in the video that it was a little bit opaque.
In the future, I plan to revisit the reaction called the Briggs Rauscher oscillating clock reaction
which also uses starch.
If i use corn starch again ill have an opaque solution and I really want to have a nice clear one.
So for this I need to prepare some potato starch.
In general, starch is stored as granules in plant cells and to get it out we need to destroy the cells.
To get this starch from potatoes we just need to mechanically break the cells apart using something like a cheese grater
and then seperate the starch from the potato shavings by washing them with water followed by filtration.
The process that I show in this video isnt the most efficient
but I still do get a decent amount and a little bit of starch tends to go a long way.
For the extraction of starch from potatoes we want to use ones which have the highest starch content
and these are the Idaho potatoes and the Russets
for this video I'm using four large Russet potatoes
but the size really doesn't matter and if you use smaller ones you'll just have to do a lot more peeling.
So speaking of peeling, I went ahead and I peeled all of the potatoes, simply using a potato peeler.
I placed the potatoes in a glass dish and then I used a cheese grater to grind them up.
Its very important that when you're doing this you don't get too excited and accidentally shave your finger a little bit
so be careful.
The starch that we are trying to extract is stored and held inside the cells of the potato
and to get it out we have to destroy the cells.
Ideally the best way to destroy the cells would be to completely crush the potato and turn it into a paste,
but that can kind of make it a little bit messy to work with.
I find that its better just to shred the potatoes, because even though the yield of starch is less
its a lot easier to work with than a mashed up paste.
if we're pretty quick, just after a few minutes we should be nearly done shredding all of the potatoes.
Once we are done shredding everything, we don't need the cheese grater anymore so we can clean it and out it aside.
To all of the shredded potatoes we then add a bunch of lukewarm water.
The amount of water that's used is pretty arbitrary and it really depends on how many potato shavings you have.
When the potatoes were shaved, a lot of the cells were destroyed and they released their starch
and we're just trying to wash away the starch into the water.
Starch is really not very soluble in water, so once we are done we will have a mixture of potatoes and starch floating around.
I did the extraction in this glass dish for demonstration purposes but it really isn't the best thing to use.
I would recommend using something like a plastic bucket or container because its a lot easier to pour from.
Once we feel like we've done a good washing of the potatoes, the next thing that we do is we try to pour off the liquid.
We try to hold back as many of the potato pieces as possible but inevitably some will be poured out.
This is okay though because the first few washings are just rough washings and it really doesn't matter.
I went ahead and washed the potatoes a couple more times using roughly the same amount of water.
After the third washing my bowl was nearly full of water, and I felt like the potatoes had been washed adequately.
At this point, we are pretty much done with the potatoes and you can either throw them out or use them to cook something.
Anyway, what we do now is we let things stand and the starch should slowly settle out at the bottom
I let things sit for about an hour and when we come back we can actually see that there is quite a bit of starch.
We really just want the starch and we can get rid of the upper water portion
so I expertly decant it off.
We get rid of most of the water and we leave just a little bit covering the starch at the bottom.
I then set up a strainer over a beaker
and i filter our starch potato mixture.
The starch is a hard clump at the bottom of the bowl so its important to mix it up before you try to filter things.
The strainer worked pretty well
and it actually stopped pretty much all of the potato pieces from going through.
A quick water washing is also done to get rid of any starch that might remain in the bowl
and also to wash the potatoes a little bit.
The strainer is then removed and these potatoes can also be thrown out or used for something else.
We let it sit for a bit and just after a few minutes we can already see some starch collecting at the bottom.
After leaving it for an hour, the solution has darkened a lot and we can see a lot of starch at the bottom.
This brown water above contains little to no starch
and we don't really want it so we just decant it and get rid of it.
To try and clean the starch up we pour in a little bit of distilled water and mix things around.
The starch is then mixed very thoroughly to make sure that all of it comes in contact with the water
and gets a good washing.
Once we've mixed things for a while and we're satisfied that everything is washed quite well
we let it stand for a little bit and allow the starch to settle to the bottom again.
When we come back in 20 or 30 minutes we again have a brown solution on top which we decant off.
More distilled water is then added to the starch
its thoroughly mixed and the starch is again allowed to settle at the bottom.
After the second and third washing, the water was only slightly discoloured
and for me I felt like this was clean enough.
Using a spoon I transferred all of the starch to a watch glass to dry.
Like cornstarch it can be fun to play with but when i did this i kind of cracked my watch glass in half.
When this happened I just quickly transferred it to a piece of printing paper
with a little bit of paper towel underneath
and I left it out for a few days to dry.
After leaving it out for a few days to dry
I'm left with about 47 grams of nice, crispy potato starch.
Like I said before, my purpose in making this is to revisit the Briggs Raucher oscillating clock reaction
but if you guys have any other cool suggestions on how I can use it, please let me know in the comments.
Anyway, as usual, I would like to extend a big thanks to all of my supporters on Patreon
and especially those who donate five dollars or more.
Anyone who donates and supports me on Patreon gets to see my videos 24 hours before I release it to YouTube
and if you donate five dollars or more, you get your name at the end of the video like you see here.
In the next few months though I want to work on my Patreon page a lot and I want to get more rewards going
and maybe even get some higher tier ones
and I also want to offer some Patreon exclusive content.
Also as usual here are the videos I've currently filmed and the ones I plan to work on
If you have any suggestions or ideas please feel free to leave them in the comments.