Question:
I’ve found a recipe in a magazine with instructions to soak Brussels sprouts in cold water with a teaspoon of baking soda before cooking to make them greener. My mother used to do this back in the 1940s but stopped when told it destroyed the nutritional value of the vegetable. Has the thinking on this changed?
Answer:
Brussels sprouts are either beloved or despised, depending on how your mother cooked them. In the 1940s, adding baking soda to the cooking pot was as common as slathering butter on toast – until nutrition scientists revealed it may rob vegetables of their health benefits.
Fast-forward to today, and a recipe has you plunging Brussels sprouts into a baking soda wash again. So, has science changed its mind on this kitchen hack, or are we potentially farewelling our vegetable’s valuable vitamins?
We often choose particular vegetables for their valuable nutrients, but recent studies have shown that how we prepare and cook our vegetables can cause various chemical changes that can enhance nutrient availability or result in significant losses.
Baking soda has become more popular in the 21st century, thanks to it being seen as an eco-friendly, affordable and versatile cleaning agent. It is also a beloved ingredient for home bakers as a raising agent. Baking soda reacts with acids (like vinegar or lemon juice) and moisture, producing carbon dioxide gas that causes dough and batters to rise, producing light and fluffy baking.
However, when it comes to vegetables and baking soda, things are not as straight forward. First, yes, the alkaline nature of baking soda does initially reduce colour loss during cooking – resulting in greener cooked vegetables such as spinach, broccoli and green peas. However, although the dunking may produce lovely-looking, green vegetables, they may also be less nutritious.
Vitamin C is often used as a marker to track nutrient losses in research, as it is highly sensitive to temperature, UV and pH levels. Studies suggest that alkaline pH levels from around pH8 upwards may induce greater vitamin C loss, although the nature of this loss is greatly complicated by the presence of minerals, temperature and various other factors.
Another study found greater losses of vitamins B1, B2 and B3 occurred when raw legumes and beans were soaked in an alkaline solution compared to plain water. Plus, the alkaline-treated veges had greater nutrient losses during the cooking process, too.
Baking soda can also break down the pectin in vegetable cell walls, leading to mushy, overdone vegetables. Alkaline cooking environments can also change the flavour of some vegetables, as chemical interactions occur between the baking soda and natural components within the vegetables.
We must place the potential for baking soda-induced changes into the wider context of all the other various factors that affect vegetable nutrient losses in the kitchen. Everything from cutting technique to peeling, water levels, mode of cooking (microwave, steaming, boiling or sauté), temperature and cooking time will affect nutrient losses. For example, even if you don’t dip your Brussels sprouts in baking soda, you might lose as many nutrients by cutting them into small pieces and boiling them.
Many complex trade-offs unwittingly occur when we prepare and cook our vegetables. Do we aim to improve their visual appearance and risk nutrient losses, or vice versa? From a nutrition perspective the motto is “less is often more – minimise interference to maximise nutrition and flavour.”
