Last night the water in this sunbutter jar, which had been left to soak in the sink, was discovered to be a dark bluish green. Dan asked if we had washed paintbrushes in the sink. We had been out for most of the day and no art supplies had been used at home, that I could think of. It didn't make any sense that soaking the jar would turn the water green, but determined to see if it would happen again, I emptied the water, filled the jar with fresh water, and added a squirt of soap, just as I had the night before. It's not as dark as yesterday, but the water is definitely greenish.
These accidental discoveries are one of my favorite things. I feel compelled to get to the bottom of the mystery. Had the sunbutter (a spread similar in consistency to peanut butter, made from sunflower seeds) reacted to the dish soap? Was the soap a red herring, did immersion in water cause some kind of oxidation reaction?
It turns out that sunbutter is known for its odd propensity to turn cookies green when it's used in a recipe. The solution to this problem (if indeed you consider it to be a problem; I consider it to be awesome) is to add lemon juice and/or reduce the baking soda or baking powder in a recipe.
Photo via waffles-n-trees. Some find green cookies disturbing. I find them awesome.
It turns out this nifty effect is due to the presence of chlorogenic acid (C16H18O9) in sunflower seeds. If you go back to your high school chemistry, you might remember that acidity and basicity are measured using the pH scale; solutions with a pH less than 7 are considered to be acidic, solutions with a pH greater than 7 are considered to be basic or alkaline, and solutions with a pH of exactly 7 are described as neutral. My internet research reveals that when chlorogenic acid is added to an alkaline solution and the solution is exposed to air, the solution turns a bluish green color.
Guess what's alkaline? Soap. And remember my acid-base reaction vs. oxidation hypotheses? Turns out it's really kindof both.
I shared my observations with Griffin, who had also noticed the blue-green water the previous day. Before hearing my hypotheses, he understood why I had attempted to replicate the previous day's conditions and suggested that the water today was less vividly green because there was less sunbutter residue inside the jar. He also suggested testing my hypotheses with two jars - one containing only water and one containing soap and water. I immediately felt like a fool. With a dual hypothesis, why hadn't I attempted to test them both? I posed the one-jar problem to Griff: how can I run two tests when I only have one used-up jar of sunbutter? His solution: try with water first, then add soap if the color hasn't changed after a certain amount of time. We agreed that one day was an appropriate amount of time, since an obvious change had occurred in both of my batches of water after 24 hours.
Now we're itching to test out our evolving hypotheses, and have determined that we can run a more scientifically rigorous study if we purchase new sunbutter, place identical portions of sunbutter in multiple identically-sized jars filled with a specific amount of water, then subject each jar to slightly different conditions so that we can determine which factors contribute significantly to the color change. I was pleasantly surprised that Griff could come up with various study conditions on his own and demonstrated an understanding of hypotheses, hypothesis testing, and study controls. The conditions we decided upon include:
1. sunbutter/water without lid
2. sunbutter/water/soap without lid
3. sunbutter/water with lid
4. sunbutter/water/soap without lid
I also shared the green cookie conundrum with Griff and told him about the effects of adding lemon juice or cutting down the baking soda. He proposed two additional conditions:
5. sunbutter/water/soap
6. sunbutter/water/soap/lemon juice
We could, of course, do each of those with and without a lid, too, yielding 8 total study conditions. What's more, we could also design conditions with and without the addition of another base, such as baking soda. I think adding that level would bring us to 16 conditions, which feels overwhelming to me, so perhaps for the first round, we'll stop with lemon juice.
This is very exciting. My favorite discoveries - and the ones that stick with me the most - are those I stumble upon like this. Can you tell the sex of a butterfly from its chrysalis? How can you see a slug's internal organs without killing the slug? How do slugs breathe? What are nasal conchae shaped like? What are those funny moving bits of sticks on the bottom of a stream? How do ladybugs develop? What is that orange thing on a swallowtail caterpillar's head? The answers to all of these, the journeys that led to them, and more are in the science catergory of this blog. Science is so cool.
