So I was doing some research on tannins and how they make tea bitter when I came across a forum saying that the secret to super smooth Sweet Tea was to add a pinch of baking soda. For those of you who haven’t had Sweet Tea, it’s a style of iced tea made in the southern United States. It is, as its name suggests, hella sweet. According to an article I found on Slate, “22 percent of the liquid consists of dissolved sugar solids, or, to put it in more meaningful terms: close to twice what you’d find in a can of Coke”
Oh my. This forum was recommending adding a tiny amount of baking soda to counteract any bitterness. So, for kicks, I got out my most astringent tea (and right now, my least favorite) Sunny Citrus (read that review here), and added a tiny pinch of baking soda to my cup after infusion. Holy Carp Batman! That tea was smooth! (Also it turned blue and fizzed a bit.) Clearly this called for science. The following is a pretty basic (tee hee) overview of what’s happening here on a chemical level.
If I add a small amount of baking soda to astringent teas, I can make them more palatable and therefore, more enjoyable. The baking soda is going to do this by altering the pH level of tea and bring it from an acidic solution to a basic state.
So, chemically speaking, baking soda is really interesting. It can be used to create a buffer solution, which means it’s a component of a chemical solution used “to prevent changes in the pH.” Baking soda is famously used by some aquarium lovers to maintain a fish friendly pH environment because it’s so good at resisting changes.
On the simplest level, the pH scale measures the acidity and alkalinity of substances. So for example, lemon juice (pH 2.2) is more acidic than water (which at pH 7 is neutral). Baking soda has a pH of 8.3. Obviously, the next question to ask here is “how acidic is tea to begin with?” Some researches measured the pH of black tea at 4.9 while they were doing research on tooth erosion, but hibiscus is way more acidic than that. When doing a study monitoring Karkadeh (hibiscus) tea’s effect on blood glucose levels, the scientist team measured hibiscus tea’s ph level at 2.5.
But why would the mixture have turned blue?
I think the answer here lies in anthocyanin, a chemical compound that gives various plants/fruits their color. Blueberries and blood oranges are a great example of anthocyanin at work. Anthrocyanins typically change color when the pH balance of a mixture is shifted. An acidic solution with anthrocyanins is red (like a red wine) but can become blue when a neutral or basic solution is added (like water or baking soda).
Anthrocyanins are of course, found in hibiscus which is why adding the baking soda buffer shifted the color of the tea.
But why did the tea fizz?
I need you to think back to your grade 7 science fair. Remember that kid with the volcano who made it explode with vinegar and baking soda? The same thing is happening here, just you know… not all over your classroom floor. http://www.youtube.com/watch?v=gOc04z8jHaM The acid in the tea is reacting with the baking soda and producing carbon dioxide. Okay…actually it’s more complicated than that. What happens is that the baking soda first reacts with the acid, producing carbonic acid. Carbonic acid then decomposes, producing carbon dioxide, which creates the bubbles.
So this means..?
In small amounts, baking soda can totally turn around a acidic/astringent cup of tea. You need the tiniest amount, less than 1/8th of a tsp. Any more than that and you can kiss that cup of tea goodbye. We can totally apply this to other cooking quandaries. Too sharp pasta sauce? Baking soda. Stingy lemon-aid? Baking soda. An entire 8 cup pitcher of tea? 1/8 – 1/4 tsp of baking soda. Some folks suggest covering up astringency/bitterness with sugar, but I don’t think that’s really fixing the problem. Sure, with enough sugar you can hide almost all culinary sins, but you need a ton of sugar to do it. By then, you’re basically drinking pop. Why fill up on totally empty calories when you can just use science?