I read this book FoodLab – all about scientifically testing new and old cooking techniques to see what actually makes a difference to taste, ease of cooking, etc. and the chemistry behind various techniques. I was just reading it out of interest, but there was a sweet potato DIY sous-vide technique that required only a large pot or beer cooler of water, instead of a $1000+ water bath machine. So that sounded cool and worth trying, especially when I thought about the collection of varieties of sweet potato that I have been passing by at the farmer’s market (on my way to the squash, of course). Sous-vide is a technique of very slowly cooking meat, veggies, fish, etc. over several hours in a bath of warm water, sometimes in a vacuum sealed (or freezer) bag. Then the food is cooked in some other way – a steak is quickly seared, or a sweet potato is roasted, etc. The idea is that sous-vide enhances the flavour of the food in some way. In the case of the sweet potatoes it is supposed to turn more of the starches to sugars, much like caramelizing onions requires low, slow heat.
So, I track down the farm and names of the Wychwood farmer’s market’s main sweet potato seller, and contact Bob and Juli from from Round Plains Plantation, to ask them to sell me a mix of the varieties of sweet potatoes that they have. I got:
- Orleans – an orange sweet potato
- Bonita- a yellow-skinned yellowish-white sweet potato
- Murasaki – a purple-skinned white sweet potato
- Satsumaimo, a purple-skinned sweet potato with deep purple flesh
I started out by sous-vide cooking all four sweet potato varieties following the FoodLab technique, then tasted all four after cooking a few different ways.
After just the sous-vide the sweet potatoes were just cooked. The different flavours between the sweet potatoes were hard to differentiate, and overall were muted. The Satsumaimo stood out as being noticeably less sweet, and the Orleans sweeter than the others.
Sous-Vide Then Roasted With Olive Oil, Salt and Pepper
Roasted, the orange Orleans was very sweet, carrotty, and just what I think of, when I think of a typical orange sweet potato. It was a good benchmark to compare the other sweet potatoes to. If it was a squash, it would be a medium quality butternut, I guess. The Bonita was earthy, just pleasantly sweet and starchier than the Orleans. The Satsumaimo had smooth, dense flesh with just a hint of sweetness at first, but that intensified after I swallowed it. Finally the Murasaki was just absolutely creamy: so smooth that it almost dissolved in my mouth. It was sweet but with a more complex flavour than the Orleans, and less dense than the Satsumaimo.
Sous-Vide Then Steamed
The Orleans, yet again, stood out as being very sweet, especially compared to the Bonita and the Satsumaimo. The Bonita and Murasaki tasted very similar – just a hint of sweetness, and very dense: if they had been a winter squash, I would consider the taste and texture amazing, like the best of the kabochas. The Satsumaimo was mildly sweet, dense, and meaty.
I also had a few spare sweet potatoes, so I did steam then bake (no sous-vide) a Satsumaimo. It was great – I noticed a slight cocoa flavour that hadn’t come out (or I hadn’t noticed) before.
Overall, the Satsumaimo was my favourite for the denseness of the flesh, and the complex flavour that seemed to differ slightly depending on the cooking method. It was closely followed by the Murasaki – also flavourful and dense. I would happily eat the Bonita any time; the Orleans is what it is, I suppose: the sweet potato for people who want a normal sweet potato.
Between my love for Kabocha squash and my top two sweet potato choices, I guess I am a fan of Japanese varieties of starchy vegetables…