Nutrition isn’t simply what you eat. Right up there at center stage, is how you prepare what you eat. The following advice has been carried forward to the present day via many culinary lineages across the planet. In fact, a few of you may have even observed your very own Grandma (especially if she came from a Greek or Italian background) dutifully employing this strategy – one that their own mother or grandmother had taught them, without necessarily knowing why they were doing it. I am referring to the soaking of potatoes, root vegetables (and also starchy fruits, typically treated as vegetables, like the entire pumpkin family) prior to being roasted, fried or baked.
Over many decades, or even hundreds of years, communities worked out that pre-soaked root veg was more sustaining and digestible than their unsoaked counterparts. Soaking starch-rich vegetables in water, especially (sea) salted water, which might also include a tablespoon or so of high-quality vinegar, for 2 – 12 hours, helps achieve something very notable. It dramatically lowers the chance for acrylamide – one of the most ubiquitous carcinogenic substances in both traditional and modern diets – to form. For more information on acrylamides, do see my article here. Put simply, Acrylamide is a naturally occurring chemical that forms when starch-rich foods are cooked at higher temperatures, such as frying, baking, grilling or roasting. When starch-rich veg such as potatoes, yams, sweet potatoes, butternut squash, pumpkin, swede and turnip (and a 100 or so others that fall into the same category) are soaked in water for 2 hours or more, with a more optimal length of time being 4 hours, or overnight for bigger items, starch molecules around the periphery of the vegetable are released into the soak water, making them less available to cause burnt browning reactions on the food surface.
Essentially, there is a significant reduction in the material that fuels the production of acrylamides on the surface of the food – the principle area where acrylamides actually form. So long as foods are not overcooked, the reduction of acrylamides is significant, ranging anywhere from 30-60% depending on how small your veg is cut and how long you actually cook it for. For best results, peel and chop the veg to your preferred size (smaller pieces relinquish the starch into the water more quickly and do not need to be soaked so long), soak in sufficient water, add sea salt, and if you are ok with it, vinegar too. You will see the water gradually turn milky as the starch is released. After you have finished the soak, give a final rinse, strain for a few minutes and then cook in your usual, preferred way. The added bonus to all of this is that the root vegetables will oftentimes come out less stodgy (too much starch concentration creates a gluey consistency), and the veg will have a creamier taste/texture. Also, roots like turnips, which can often have some bitterness to them, are debittered by their bathing time.