The triumphs and toxicity of eating lupins

I keep coming across recipes in low carbohydrate cook books which use lupin flour. “Lupins are everywhere, I could just harvest them,” I thought. So, I was at the beach gathering lupin seeds, when a passing woman asked me what I was doing. When I told her, she let me know that wild lupins are toxic and should not be eaten. That was another lucky escape. I would not have lasted long in a hunter-gatherer society. I went sadly back to my computer to find out which lupins are edible, and where to get the seeds. I eventually found some edible lupin seeds at the Koanga Institute. They are called Lupinus mutabilis or Andean Tarwi and are a staple crop in South America. I grew a small crop, having no idea what sort of plant I would get. I ended up with a patch of small shrubs about 50cm tall that produced fat green seed pods very similar in appearance to small broad beans. Once they were harvested and dried, I got about two cups of unusual white flattish beans. I had expected to just grind them into flour but, unfortunately, the process is much more involved than this, as the beans contain toxic, bitter alkaloids. I had to soak the beans for 24 hours, boil them for 90 minutes, then submerge the drained beans in fresh cold water, changing the water daily for about a week. The test for doneness is to bite into a bean and if it still tastes bitter, more soaking is required. Now, if all of this sounds too hard, clever Australians have managed to breed (without genetic engineering) a sweet lupin bean that contains no bitter alkaloids, and can be used in cooking without a week’s worth of processing. Unfortunately, this variety, called Lupinus angustifolius, is only available in Australia. It is possible to buy the Australian sweet lupin flour, or a flaked version for making porridge, but not the whole beans. To add to the confusion, blue flowered lupins, used as a garden cover crop, are also called Lupinus angustifolius, but these have not had the bitter alkaloids bred out of them. The Australian sweet lupin is grown as a harvestable crop in wheat-growing parts of Australia, in rotation with wheat, because it breaks cereal disease cycles and improves soils as it has a deep tap root that pulls up deeper nutrients unavailable to cereals and fixes nitrogen in the soil. They are also drought-tolerant and can handle poor soils. The beans are used as stock food and for human consumption. Here are some nutrition facts: Sweet lupins contain 30-40% protein, 30-40% dietary fibre, only 4% carbohydrates, are gluten free, very low GI and contain only 4-9% fat. They are rich in vitamins B1, B2 and B3, also folate, magnesium, phosphorus, manganese and iron. They also contain a complete profile of nine essential amino acids. The high protein and fibre combine to promote a feeling of fullness (I can vouch for this as I could not finish the lupin flour-based pizza I made for dinner). Something to be aware of if you have a peanut allergy, sweet lupins come from a similar family to peanuts and can have the same effect as peanuts. Lupins can also be a good alternative to soybeans as they have similar dietary benefits but are not grown in deforested parts of the Amazon. Hilary RowleyDrying seeds from the modified lupin cultivar, Lupinus mutabilis or Andean Tarwi, which were sourced from the Koanga Institute. They’re edible but require a lot of processing. Back to my home-grown magic beans — I went through the whole soaking-cooking-leaching process. I set aside some to dry for later use and made some into “milk”. As far as plant milk goes, it had a good flavour, was an unusual creamy yellow colour, but has the benefit of nearly as much protein as dairy milk, so I considered it to be a success. I ground some of the processed and dried beans into flour using my trusty coffee and spice grinder, mixed it with almond flour and made a low carbohydrate pizza base. Because of the lack of gluten, it is necessary to add some xanthan gum so the dough has stretchiness. The pizza was a total success, and better than other low carbohydrate pizza bases I have tried. Other uses are hummus, porridge (made with flaked lupin), used as a bean replacement in stews, and many other types of baking. I think that the sweet lupin, especially the Australian variety, has a lot of potential as a drought resistant crop in New Zealand, both as stock food and food for humans. Another observation is that when two quite different cultivars have the same botanical name, it is going to lead to confusion and possibly poisoning. While researching this article, I had to put a few people straight who were thinking about growing blue lupin from Kings Seeds for eating. It is only the modified Australian cultivar that is edible. Surely this needs a new botanical name? Whatever you do, don’t try eating the wild beach lupins or Russell lupins. If you can’t be bothered with all this growing-harvesting-processing lunacy, just buy a bag of lupin flour from a whole foods shop. Hilary Rowley is a frugal, foraging foodie from Waitati. Each week in this column writers address issues of sustainability.