Mashing Potatoes

[YHB]

This is “what I did” not a “what to do” story.

I really like the idea of making spirits from just potatoes. It would be really cool to make it from potatoes you have grown, a bit like having a Vodka Tree in your garden.

I have done enough reading to really confuse myself and received some advice from people who know more about the subject than me, but their advice only confused me a little more. Expressions like Mashing, Lautering, Sparging, & Spike Temperatures make my eyes go all blurry

What I needed to do was try it and see what happens and then I might understand what is going on a little better.

I have read that 1 kg of potatoes contains 0.1kg of starch which can be converted into 0.1 kg of fermentable sugar. I decided to make a 5 litre mash with 10kg of potatoes as a trial batch so I bought 5 Kg of budget potatoes for £2.28 from Sainsbury’s. Maybe these spuds have 10% starch maybe not?

I put the potatoes through a juice extractor, the 10 kg gave me 3.5 litres of “potato juice” and about 1 litre of dry shredded pulp – I binned the pulp.

I let the juice settle and the potato starch just settles to the bottom, it is insoluble in water at room temperature and it feels exactly like corn flour, which thinking about it should not be a surprise because they are both basically the same stuff.

Various reads have stated that the potato starch needs to be boiled to breakdown the cell walls. I do not know if the juice extractor destroys the cell walls or not but it seemed like a good idea to give it a boil.

Heated the liquid up – before it boiled it thickened and thickened and became a solid blob -I added some water so that it resembled a very thick wall paper paste.

I tweaked the temperature with cold water / heat until it was 155degF and then added a teaspoon of Amylase, within ten minutes the goo was the consistency of double cream after 30minutes it was like water, Tasted it – sweetish .

I put the soup back on the heat and brought it up to the boil, the Analyse must have done something, because it did not thicken any more. I let it simmer for 45 minutes and turned it off to cool. When it got to 155 deg F I added the second spoon of Amylase and kept it at that temperature for half an hour.

Switched off and washed up.

If you believe the hydrometer, after the first batch of Amylase the SG was 1.045, after the boil and the second dose of Amylase the SG was 1.065 If I fermented that dry then the net result would be 3.5 litres of 9%, looking at the amount of solids in the demijohn and therefore the amount of wastage I think I will be lucky to be able to siphon off even 3.0 litres.

3.0 Litres of 9% from 5.0 Kg of potatoes is a bit disappointing to say the least.

Anybody any thoughts./ ideas / tips / experience of other enzymes / mashing temperatures / techniques.to get more sugar out of the potatoes?

In the meantime I will keep on reading.

Toodlepip

[Almanac]

Ditto. The juicer does work well at extracting the starches from spuds. I sparged (rinsed) the pulp in hot water before dumping it but I'm not sure how much, if anything, this added in terms of fermentable sugars.

I think boiling is unnecessary as the starches gelatinise, or get really thick, around 65-70oC and this is around the ideal temp for the enzymes too.

If you add 10% by weight of malted barley to the liquid at the start, then when it gets to 65-70oC the natural enzymes in the malt will counter the thickening too, as well as adding a little more grain sugar to the mash.

However, I too found the return from spuds did not justify the cost. I suppose if you had a bumper crop of spuds you had grown yourself and no market or demand for them it might be worth using them for making alcohol but if you have to buy them Not for me.

AM