We’ve heard the claim that baking soda is sometimes used when boiling vegetables to preserve their color. We wanted to know if this really worked.
To find out, we boiled broccoli, asparagus, green beans, and red cabbage in a gallon of water with ¼ teaspoon of baking soda and compared them with the same vegetables boiled in unadulterated water. We got some surprising results. Baking soda does help green vegetables retain color, but it causes undesirable color changes in red cabbage—it turned blue. The science can be distilled to this: Adding baking soda to cooking water makes it slightly alkaline, which stabilizes the green color of chlorophyll. The baking soda, however, turned red cabbage a scary shade of blue because the cabbage’s pigments (red anthocyanins) turn blue in alkaline environments. Baking soda also accelerates softening in all vegetables, no matter what their color.
Having tested slightly alkaline cooking water, we naturally wondered if acidic cooking water might have the opposite effect. It did; with 1 tablespoon of lemon juice per gallon of water, green vegetables turned yellowish brown yet stayed firm after several minutes in boiling water. Red cabbage, however, stayed bright red and firm in acidic water.
THE BOTTOM LINE Skip the baking soda when boiling green vegetables. The slight improvement in color isn’t worth the mushy texture. Keep vegetables green by not overcooking them and by reserving acidic finishing ingredients like lemon juice or vinegar-based dressings until serving time. Add lemon juice or vinegar to cooking liquids for red vegetables to retain bright color and firm texture.
