Can we make sugar from skirret root?

In a cool damp climate being self sufficient in sugar can be a challenge. It has been used as a preservative since antiquity. I've tried growing sugar beet in the past, and the results were not very satisfactory - the roots grew fine, but extracting and refining the sugar to a point where it was useful was beyond my skills at the time. I was surprised to find out how sugar rich skirret actually is, although I knew it was called the equivalent of 'sugar root' in several European languages.
From this abstract

the root has a greater content of dry matter (16% average) and is rich in sugars especially sucrose (65% of dry matter).

The sugar content isn't quite as high as you might think in the actual root: 65% of 16% is 10.4%, so still pretty high.
sugar beet has between 12 and 21% according to Sugar beet

For reference, the sugar content of other roots (raw) from nutitionvalue.org

carrots: 4.7
beetroot 6.8g
parsnip 4.8g
sweet potato 4.2g
rutabaga 4.5g

Has anyone actually tried to extract sugar from skirret root? I'm keen to hear of any successes or failures before I start playing.

I'm guessing much of the time, the skirrit would be used like carrot, rather than to make crystalline sucrose.

I found this paper about extracting sucrose, glucose & fructose from carrots with an interesting abstract:

Sucrose, glucose, and fructose extraction in aqueous carrot root extracts prepared at different temperatures by means of direct NMR measurements
Cazor et al. 2006

https://pubs.acs.org/doi/abs/10.1021/jf060144i

"[In] Solutions obtained by heating carrot roots in water (stocks) ..

"The concentrations of these three sugars reached a maximum after 9 h when the temperature of treatment was 50 or 75 °C. At 100 °C, the sucrose concentration reached a maximum after 3 h, whereas the concentration of glucose and fructose was still increasing at that time."

This makes me wonder if you could simmer the mascersted skirrit root overnight in the woodstove, and then measure the specific gravity to estimate the concentration of sugars?  This 'stock' could be used as a partial replacement for some of the sugar & water in a strongly flavoured chutney, at the very least.

Hi Ac! Cooking in water is one way of extracting the sugar. It is interesting that the available sucrose seems to stabilise in the water after three hours. That seems like a long time! did they macerate the carrots to maximise the surface area?
I'm inclined to start with trying to juice the roots first. I have a little hand juicer and that will avoid having more water to remove.

A syrup certainly has culinary uses. I think that one that is strong enough to keep well will be fairly viscous so I may go by eye/taste to start with. I was thinking that a refractometer might be useful for assessing root crop nutritional value and it would be invaluable for this too. I do have a hygrometer, but it needs quite a volume of liquid - any ideas of more simple ways of measuring density of liquids?

Nancy Reading wrote:Hi AC! Cooking in water is one way of extracting the sugar. It is interesting that the available sucrose seems to stabilise in the water after three hours. That seems like a long time! did they macerate the carrots to maximise the surface area?

I've finally managed to find the full paper for free (not behind a paywall):

https://ucanr.edu/datastoreFiles/608-463.pdf

which says: "Each carrot was cut lengthwise into four parts to ensure homogeneous material was being compared. These four parts were cut lengthwise into disk sectors of a 5.5 mm thickness (to minimize edge effects)."

Nancy Reading wrote:I'm inclined to start with trying to juice the roots first. I have a little hand juicer and that will avoid having more water to remove.

Since I don't have the figures for skirret (!), I thought carrot might give us a rough idea of the efficiency.  Bao & Chang 1994 estimate the sugar content of juiced carrots as c. 8-9% reducing sugars (https://ift.onlinelibrary.wiley.com/doi/abs/10.1111/j.1365-2621.1994.tb14666.x) which suggests you've extract the non-reducing sucrose more efficiently than the reducing glucose & fructose.   Other sources say, carrots are 90 +/- 5% water, and have c. 4 +/- 0.5 g of sugars per 100g and carrot juice has 4 g sugars per 100 g, and has a density of around 1.01442 g/cm3.

So it sounds like juicing works pretty efficiently for extracting sucrose from carrots.

Given the high proportion of sucrose in skirret, as long as the flavour isn't a problem, skirret juice sounds promising for reducing the need to add 'shop bought' sucrose to wet dishes!

Nancy Reading wrote:A syrup certainly has culinary uses. I think that one that is strong enough to keep well will be fairly viscous so I may go by eye/taste to start with. I was thinking that a refractometer might be useful for assessing root crop nutritional value and it would be invaluable for this too. I do have a hygrometer, but it needs quite a volume of liquid - any ideas of more simple ways of measuring density of liquids?

It's much easier to compare densities, than to exactly measure them, of course!  You could I guess calibrate a kitchen balance between water at the light end of the calibration line, and a stable syrup (e.g. golden syrup, which consists of fructose, glucose & sucrose with a density of around 1.430 g/cm3) at heavy end?

I'll post some pictures later (when I can find the camera lead...) but thought I'd note down my progress so far.

I dug up 4 rather congested skirret plants today, separating just over 1 kg of useful roots. They snap off fairly easily and the plant can then be divided and replanted. I washed the mud off the roots in my water terraces and gave them a final rinse in the stream. There was maybe a bit of dirt still in the root creases, but fairly clean. I (eventually) found my hand cranked vegetable juicer and fed the skirret roots through. The good news is that the root goes through the juicer really easily. The bad news is that the juice doesn't really flow well. It is rather pulpy, so although some dryish pulp is pushed out the end, the juice that drips out the other end is still rather thick and pulpy. There is no way a viscosity test would give an accurate estimate of sugar content, as the density is increased by the pulp content. Tasting the juice and comparing it to the dry pulp indicates that most of the sugar is in the juice however. The juice is much sweeter to taste. I got about 1 UK pint /  500ml of pulpy juice, and about 20 ounces of dryish pulp from my roots.

I have made an experimental cake (no added sugar :P ) from the dry pulp. I'll post the recipe for that separately after I've tasted it. The rest of the juicy pulp and dry pulp are currently in the fridge whilst I consider my next move, and ask for advice here. At the moment I'm thinking of just processing the juice as it is - warming it on the stove on a gentle heat to dry it. I'll just see what happens as it dries out. I don't think there is really enough to try too many ways of processing it, and for most of my uses a bit of extra fibre, given the flavour is pretty neutral, won't be a problem.

I may have enough plants left to try pressing the juice out using a press and cloth like for cider. I feel like that will be a more wasteful process (so much is left in the cloth) but ought to give a 'cleaner' juice as a result.

Any thoughts or suggestions so far?

Not sure about skirret, but our pressed apple juice was so sweet this year that I experimented with cooking a gallon or so down into a molasses. It's tough to get there without it turning gelatinous from the pectin, but the result was a lovely sweet syrup. I'm sure something similar would be possible with skirret juice.

I haven’t tried extracting sugar from skirret myself, but it’s definitely an intriguing idea! Skirret’s sugar content is impressive, and with its long history as a "sugar root," it seems worth experimenting with.

Pictures as promised:

Wonderful!  How is the cake?!?!

Ac Baker wrote:Wonderful!  How is the cake?!?!

Actually not half bad! It has turned out a little dense perhaps. I'm going to start a new thread on cooking with skirret to avoid derailing this one.

C Murphy wrote:Not sure about skirret, but our pressed apple juice was so sweet this year that I experimented with cooking a gallon or so down into a molasses. It's tough to get there without it turning gelatinous from the pectin, but the result was a lovely sweet syrup. I'm sure something similar would be possible with skirret juice.

Thanks for sharing your experience! I don't think skirret has pectin in so it oughtn't to gel. There is something jelly like in the 'juice' I have though - it still has quite a bit of fibre in I think. I think I will try cooking it down though and just see what happens.

Next time I will try cooking in water and straining off the roots. I didn't want to do that since it seems poor practice to add more water just to remove it later, but it may be the only way of getting clean sugar. The fibre may not matter, depending on what I'm likely to do with the sugar. It wouldn't matter in jams or baking. Maybe not so good in cordials though, but they often get strained anyhow.

Looking through this thread, I am impressed by your patience! I'm feeling very labor-averse at the moment, so this has me thinking of more direct, much less fiddly ways to use the sugar inside. Perhaps the roots could be finely grated and mixed with a sour fruit, then baked in a pie? Add grated to (pan)cake batter, cook with grains for porridge, etc?

I have some skirret seeds (that I hope are still good!) and maybe someday will be able to experiment with my own!

I wonder if steam juicing would extract more sugars than mechanical juicing?