I wanted to harvest some turmeric to process into the spice, but it was summer (when the solar food dehydrator works best). Unfortunately I found out by experience that the rhizomes are very small and straggly during the warmer parts of the year and the best harvest time is late autumn and into winter. Lesson learned!
So now (June 2021) it was pretty cold in the back yard so I went out and dug around in the self-watering earth box and found some nice rhizomes to play with and process, while still leaving plenty to grow. This is what I found –
Cleaning
The rhizomes have quite and uneven surface and seeing as I have never really been a fan of dirt curry, the first chore was to make sure they were squeaky clean. Initially I gave the rhizomes a good wash off with tank water outside, then took them inside and broke away any of the branched ones so that there was no dirt trapped in the areas between to branches. It was then a simple matter to remove any remaining dirt with a stiff veggie brush in the kitchen sink.
Boiling
The rhizomes need to be boiled before processing further. The boiling process gelatinises the starch in the rhizomes resulting in faster drying time and more even distribution of the rich colour which turmeric is known for throughout the rhizomes being dried. It also removes the ‘raw’ aroma and makes them soft and easier to work with.
To boil them up I placed them in a pot with plenty of cold water in it, 20mm – 30mm over the top of the turmeric. I then used our solar powered induction cooker to bring the pot to the boil, reduced it to a simmer for about half an hour. The end point of the process is being able to pass a skewer easily through one of the rhizomes and once I could do that I removed the pot from the heat and fished out the turmeric to cool on a rack.
Drying
As previously mentioned, I had it in my head to use our solar drier to dry the cooked turmeric, but being winter and the weather was lousy for dehydrating food, I elected to borrow an electric dehydrator from my daughter and use that. There was another issue also – from previous experience I know that the best I can get out of my solar offset drier is 60⁰C, while the books I have read specify 70⁰C as the best temperature. Is the extra 10⁰C significant? I have no idea! But I thought I should mention it anyway and the dehydrator I was using would go up to 70⁰C, so that was it!
To prepare the rhizomes for drying once they have cooled it is just a case of slicing them up into 3mm or so thick rounds, across the rhizome. They should then be placed in one layer over the dehydrator tray and dried until nice and hard and brittle. I had read that this could take some time so I set up and let it go. I put it on just after lunch and was considering leaving the process go overnight but when I checked about 7:00pm they all looked pretty dry to me so I just removed the drying tray and let them cool for a couple of hours, before placing the dried bits in a sealable glass jar.
Grinding
While being a fun process, it has not given us the powdered spice we are looking for so the next trick is to grind them up. We have a spice/coffee grinder, but I am sure you could get away with using blender or some such. I tossed a small handful of the dried turmeric into the grinder and ran it for several bursts of a 10 to 15 seconds each. This resulted in a powder of variable particle size, so I sieved out the fine stuff using a kitchen sieve and returned the bigger stuff for another round and so on. I think I need a finer sieve but generally the powder seemed to work well when incorporated into a veggie curry!
OK, the next bit is based on very little thought and not much evidence, but here goes anyway! It is a generally accepted fact that whole spices will retain their flavour and aroma longer than the ground variety, mostly due to the very fine particle size of ground spices allowing volatile compounds to escape. Based on the same theory, we are retaining the dried turmeric rhizomes in the glass jar and only grinding them as we need to for use.
Growing and Processing Turmeric - Part 1: Growing
