Pumpkin skin miso
This is part of our series on upcycling fruit & veg by-products.
Table of Contents
i. Making the most of a winter staple
For many urban dwellers, the eye-catching shapes, colours and sizes of different pumpkins (or winter squashes) for sale at a farmer's market might be something of a gateway drug, giving a glimpse into the possibilities of agrobiodiversity, and a reminder of how much more diverse and beautiful most of our daily diets could be (again).¹
Originating in the Americas, pumpkins have been cultivated as a staple crop by indigenous people for about 10,000 years and were famously grown with beans and corn as part of the ‘Three Sisters’. In this ingenious form of polyculture, the pumpkins shade soil to keep it moist and outcompete weeds, and the beans fix nitrogen and anchor the corn whilst climbing up their stalks—all while yielding more calories and protein per hectare than if each crop were grown in monoculture.² Polycultural practices like this could become more common elsewhere in agroecological futures.
A typical pumpkin might yield between 66-75% of its mass as edible flesh, with the remainder made up of skin, seeds, stalk and pulp.³ While many people only eat that flesh, the skins of most varieties are not only edible but are highly nutritious.⁴
Here we present an alternative way to use those skins, by making them into a sweet yet umami-rich miso with a light chocolatey and fruity aroma. This is an example of a translated fermentation that adapts existing techniques from one part of the world to use novel ingredients from another. Kim made this recipe using the skins of a couple of butternut squashes, but it would work for any edible variety of squash/pumpkin. Later we discuss some of the different adaptations that you could make to this recipe, and why we wouldn’t recommend using this technique for Hallowe’en pumpkins.
ii. Recipe
Ingredients
1 part, by mass, roasted pumpkin skin
1 part, by mass, textured vegetable protein (TVP) or other soy protein⁵
2 parts, by mass, kōji⁶
4 parts, by mass, water
4% of the combined mass of all of the above, salt
Method
Roast the pumpkin skin. Don’t be tempted to skip this step. Fermented cooked skins are delicious and can yield surprisingly intense flavours of orange and passion fruit. Fermented uncooked skins taste like orange juice left in the summer sun for a week.
Dry the roasted pumpkin skin in a dehydrator for a couple of hours, then grind it with TVP to create a fine powder.⁷
Mix the pumpkin skin and TVP powder, kōji, salt and water together by hand, and then combine them further using a mincer or hand grinder.
Transfer the mixture into a sanitised fermentation vessel. Cover with cling film and add fermentation weights (or a vessel filled with water). We left this in a 30℃ chamber for 3 months to speed up the process.
iii. Adaptations
Using other vegetables
When making misos from low-protein ingredients like pumpkin skin (which is ~2% protein), Kim likes to add soy protein (as TVP, a by-product of producing soy oil that has ~60% protein content) in a 1:1 ratio with the pumpkin skin. This results in a more balanced end product, with ~30% protein content that generates the rich umami flavours expected from a miso. It also upcycles two by-products at the same time, adding more value together than they might achieve alone. He observes that if you only use a carbohydrate-rich substrate like pumpkin skin with no additional protein, the result is very sweet with little umami flavour, and therefore arguably not really a miso but closer to an amazake.
This recipe could be adapted to use almost any vegetable flesh or edible plant skin, even less readily edible skins and peels, such as tannin-rich carrot and potato peels, or citrus skins. For the latter few, rather than the 3-month fermentation used to make a sweeter young miso as described above, it would be more appropriate to do a longer fermentation (~1 year) with more salt (~6-8% by mass of ingredients) to ensure that the skins have fully broken down and the end product is edible. In both cases, ensure to add a protein-rich ingredient like TVP to compensate for the low protein content of the chosen substrate.
Considerations if using the seeds
In addition to the skins, it may also be possible to use pumpkin seeds in your miso, though we’d caution against doing that without due care for a couple of reasons:
Firstly, whilst the seeds of all pumpkins are very nutritious, most varieties are covered in an inedible hard-to-remove shell. The pumpkin seeds typically available to buy in supermarkets are from a variety specifically bred for their seeds.
If you do choose to include the seeds, it’s important to process them properly. Mill them into a fine powder and sieve them if you want a smoother miso. You might be able to just roughly crush them if making a more textured miso, though the final product might be a bit gritty.
Finally, even if you do process the seeds as above, you need to consider their high-fat content. Fat oxidises and can easily go rancid, potentially spoiling your miso. Reducing the length of the ferment reduces the risk of rancidity, so you’d probably only want to make a very young sweet miso if you include the seeds.
Considering all of the above, Kim doesn’t think including the seeds in miso is worth it and suggests using them for other preparations.
Hallowe’en pumpkins
We don’t recommend using this recipe for decorative pumpkins that have been used as jack-o’-lanterns for Hallowe’en. Pumpkins with pierced flesh, that have been sat outside for a week or more with toxic candles inside, aren’t particularly food-safe or hygienic. Decorative pumpkins are also usually a specific variety, bred for their size at the expense of flavour; there’s a good reason we don’t typically eat them. Arguably, since they have been bred to be decorative they are about as much a part of the food system as decorative flowers, so perhaps shouldn’t even be thought of as food waste. As much as we are proponents of upcycling, sometimes it just isn’t worth it.
Contributions & acknowledgements
Eliot wrote the article in discussion with Kim, with contributions and editorial feedback from Josh. Kim performed the original culinary research.
This recipe has roots in Kim’s previous work as Head of R&D at the former Amass Restaurant in Copenhagen. Thank you Amass for facilitating such trailblazing work in culinary upcycling and holistic sustainability!
Eliot photographed the miso in our food lab.
Stock image credit: Leo Malsam (iStock).
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Endnotes
[1] A terminological note: we are using the terms ‘squash’, ‘winter squash’ and ‘pumpkin’ somewhat interchangeably here, in part because of the different dialects of the native English speakers in our team. In Australia and New Zealand, pumpkin refers to all winter squashes, whereas in the UK pumpkin usually refers only to orange pumpkins used for Hallowe’en decorations. We’re using the New Zealand version of the term for the title of this piece because we preferred the way it rolled off our tongues.
[2] Jane Mt.Pleasant (2016), ‘Food Yields and Nutrient Analyses of the Three Sisters: A Haudenosaunee Cropping System’, Ethnobiology Letters.
[3] Based on a medium-sized Hokkaido squash weighing 1.3kg, which, when broken down and weighed, yielded: 861g flesh, 247g pulp and seeds, and 182g skin—approximately ⅔ edible flesh. This individual squash had a particularly large amount of pulp relative to its size.
[4] Maria Batool et al. (2022), ‘Nutritional Value, Phytochemical Potential, and Therapeutic Benefits of Pumpkin (Cucurbita sp.)’, Plants.
[5] Note that TVP has a protein content of ~60%, whilst boiled soybeans are ~17%, so you can’t substitute the former for the latter without substantially changing the recipe (and the amount of low-protein ingredients that can be used).
[6] We use a standard recipe for kōji preparation, like that documented in the Noma Guide to Fermentation (2018).
[7] We’re aware that dehydrating a product only to quickly rehydrate again might seem needlessly energy-intensive, though we would argue that this is justifiable for the sake of precision. Whilst we favour using a bit more energy to create a precisely reproducible recipe, a more frugal cook/fermenter could certainly experiment with skipping this step and tinkering with how much to reduce the water (at their own risk).