Everyone has a favorite holiday food. Some may love turkey; others might go for stuffing. For me, I have two Thanksgiving favorites. First, I love my mom’s sweet potato casserole. It’s not a proper Thanksgiving without it. I could spend today talking about exactly what makes her recipe so fantastic – but that’s less of a science topic and more of a closely held family secret that I absolutely, positively cannot share. No, don’t ask me. I can’t disclose it. You can try to guess if you want, but no one has ever successfully named it.
Instead, I’m going to talk about my second favorite holiday food: cranberry sauce (and in case you’re wondering, yes, I do have a sweet tooth). But why am I talking about cranberry sauce on a science blog? Well, because there’s some really cool science behind this holiday favorite (or least favorite for some of you, I don’t judge).
For example, have you ever considered how a cranberry turns into the sauce we are so familiar with? My family’s cranberry sauce came from the canned food part of the grocery store, and, to the extent that I did think about it, I just assumed that it had the same stuff in it that Jell-O did. Jell-O gets its distinctive jelli-ness from gelatin. They both have that jelly texture, cranberry sauce must have gelatin, right?
Here’s the thing though – cranberry sauce doesn’t have any gelatin in it. Even the really jelly like cranberry sauce, the one that literally takes on the shape of the can it’s stored in, doesn’t have gelatin in it.
If cranberry sauce doesn’t have gelatin in it, then how does it get that jelly like texture? Well, cranberry sauce has pectin in it. This isn’t too surprising. Cranberries are fruit, and all fruit contains pectin. But a cranberry doesn’t just have a little bit of pectin. It has a whole lot of pectin.
Normally, the pectin helps the cranberry maintain its round shape. However, when we heat up cranberries, they start to break down. This releases the pectin that it is inside. At the molecular level, pectin is a polysaccharide (poly meaning many and saccharide meaning sugar).
Since an individual pectin molecule is so long and made up of so many individual sugars, multiple pectin molecules can easily get tangled up in each other when they get out of the cranberries. These tangles create a structure that solidifies the cranberry sauce. The longer you boil the cranberries, the more pectin is released, and the more solid your cranberry sauce.
How does this differ from the gelatin that you find in Jell-O? Gelatin has a complicated structure just like pectin. However, instead of being a type of sugar, gelatin is a protein that comes from animals. Gelatin’s structure is also pretty weak, and it breaks down easily in hot water. So, when you boil gelatin, it breaks down. But it doesn’t like staying that way, so when it cools down, it resolidifies. However, it can’t resolidify quite the way it was pre-heating. This leads to the semi-liquid/semi-solid state that is Jell-O.
So, next time you put a dollop of cranberry sauce next to the turkey on your plate, remember the properties that make the holiday favorite so unique! And, hey, now you have a fun fact to bring up when the conversation lulls around the Thanksgiving table.