“leafu”

This post is for Amanda.

Leafu or leaf curd is a way of concentrating the protein in green leaves to make it accessible to humans. Apparently you can use almost any non toxic leaf, but nettle greens are what I have plenty of just at the moment. The resulting substance is up to 70% dry weight protein, which is useful for those following a vegan diet. Although not vegan myself, I fancied having a go with my nettles to see what could be achieved. The nettles here grow rather prickly and although I know you can have nettles as a green cooked vegetable, the results here are rather less than palatable. Someone else in the glen went so far as to import nettles from Yorkshire from a known good clump – but here they also grew prickly, so it seems to be something about the environment here. Maybe they need more sheltered conditions to grow nice, so perhaps when my trees are bigger and provide more shelter I will have lush nettles again.

The recipe for leafu is very simple:

1) Collect your greens (and wash them)

2) Bash them to release the cell contents

3) Strain off the liquid from the fibrous parts of the plant

4) Heat the liquid to boiling point to curdle the protein

5) Strain off the protein solids

6) Treat if necessary to preserve the leafu.

Collecting nettles was quite straightforwards. I was using a recipe from a Country Kitchen article by Fergus Drennan which I found online (http://fergustheforager.co.uk/wp-content/uploads/2013/04/ckjuly09curdsaway.pdf) which intimates that 12kg of nettle leaf can produce 1 kg of moist leafu. I thought as a trial this was maybe a little large, so I aimed to collect 6 kg to make a pound of leaf curd. One carrier bag of nettles seemed to weigh about a kg, and I had no problem collecting 5 bags of youngish nettles – alternatively being able to collect this amount of nettles in my fruit garden could be considered to be a problem in itself! However, hopefully picking off the tops may knock back the growth a bit anyway. I did get stung a little – the gloves I like to use in the garden are the cloth type with latex palms. The nettles do sting through the fabric, so I got a bit stung on the backs of my hands. It’s supposed to be good for the circulation, or prevent rhumatism perhaps.

To bash the leaves I used a food processor. You can use a liquidiser, or a juicer, or a pestle and mortar, and probably other devices. It was quite slow and makes a mess. I would recommend not starting this job at 6 o’clock on a Sunday evening when you have to make and eat dinner and have a bath before bedtime! I started off cutting the nettles up on a chopping board and then feeding the pieces down a funnel into the processor with a little water to help it move. I soon worked out that actually I could feed the whole stems into the top of the processor which saved a lot of time. Although I thought I had selected the stems pretty well while picking them, I had to edit them a bit to get rid of a few eaten leaves, and rooty bits of stem. When the food processor was as full as I dared with liquidised nettles, I transferred the lot into a large jelly bag in my jam cauldron.

Food processor full of pulped nettle

maslin pan over-full of pulped nettle!

I found the pulp was very bulky and it more than filled the maslin pan. I decanted some liquid into a mixing bowl, even so had I actually persevered and pulped the whole 5 bags collected, there is no way my jelly bag would have been big enough. Fergus suggests using a pillow case, but I suspect at this stage something coarser would be OK – may be some environmesh insect screening? But you’d also need a larger container like a baby bath, or maybe a large plastic gardening trug? Anyway, since it was getting late and the pan was getting full I stopped after 2 bags.

I managed to suspend the heavy jelly bag over my mixing bowl and left it to drain overnight. The left over nettles went in the compost heap, as did the contents of the jelly bag the next day after I had squeezed what extra moisture I could from it. The liquid was very dark, almost black. I meant to have a go at paper making with the pulp as Fergus suggests, but forgot in the excitement of leafu production!

The next step is heating the liquid gently to boiling point and simmer for about a minute. I cook on a wood fired range cooker, so I normally use the oven to heat up large quantities, so this is what I did. I guess the oven was about 170 degrees celsius (top end of the hot on my oven door thermometer) and I then went away to do something else. When I returned sometime later remembering the leafu – it was hot and steaming with a dark coloured crust. When placed on the hot side of the hot plate on the cooker top it was already boiling gently, so I guess it must have been at boiling for rather longer than a minute. The crust was the leafu protein, so it seems to be a fairly tolerant process. I guess that if the nutrients such as vitamins are crucial to your diet, then cooking the liquid the minimum amount to coagulate the protein would be better than my extra time.

Coagulated protein layer

The solid protein is very fine particles. I used a small jelly bag which has a very fine mesh. I expect a coffee filter might be suitable if big enough, but certainly the bag I used for the initial filtering of the nettle solids would not have caught the leaf protein. Again I left the bag to drip overnight and the result was about a cup of soft solids like a dark green mousse. I weighed this as about 4oz (100g). I also had a large bowl of nettle juice (less some of the protein) which I have kept to use as plant food.

Straining off curds

Moist leaf curd

Fergus gives various methods of preserving the leafu. Apparently in it’s fresh state it will not last very long, even in the refrigerator. It keeps a little longer if you add salt (about 1oz to every 4oz fresh curd) and refrigerate, or you can freeze it in portions or dry and use as stock cubes in stews, soups and sauces. I admit I got confused at this stage and both added salt and then dried the curd (sitting in a bowl on top of the cooker for a day or so with occasional stirring). The result was about 1 and a half ounces of leafu powder, of which one ounce was salt. So I’m afraid the overall taste at the end was salt. At the fresh curd stage It tasted strongly of green. Not an unpleasant taste, but I wouldn’t expect my husband to eat it neat! He won’t notice it added instead of marmite to a stew next time I do something suitable.

Dried leaf curd and plant food (in milk cartons)

Verdict: This was a fun way to use a glut of inedible nettles. I think however, if you don’t need a protein concentrate, it’s a rather long process for a little gain. On researching around on the internet for nutrient content of leaf curd, I found a reference to someone who uses dried nettles as a condiment and I think this would be a more practical way for me personally to use them in the future. I can generally dry things in the polytunnel hung from the crop bars, or on cooling trays in the bottom oven, when the stove is on. I may have a go at this later in the year. I think that you would lose less of the other nutrients in the nettles (in the ‘whey’), although would need a greater amount of dried nettles for the same amount of protein. They do seem to contain about one third protein by dry mass (from wikipedia https://en.wikipedia.org/wiki/Urtica_dioica), so that would only need a bit more than twice as much dried nettle to have the same protein as dried leaf curd.