If you're interested at all in molecular gastronomy, you're no doubt aware that there are several books available on the subject. What you may not know is that there is only
one that's actually worth owning.
I purchased a can of Heinz-brand recently and was amazed at the fact that it somehow manages to remain in liquid state even after being opened and sitting in my fridge for a few days. Whener i make gravy, it essentially needs to be consumed while still warm or else it will congeal into a nasty inedible mass. That's a problem, expecially as a bachelor because it's very difficult to cook just the right amount of food for only one person and i basically always have leftovers.
I examined the Heinz label and found that "modified corn starch" is the second ingredient. I figured it was the most likely cause, since there were very few unpronouncable ingredients listed and i recognized most of them.
Harold McGee's book describes modified corn starch as being almost entirely of amylopectin with basically no amylose. If you've watched Good Eats, you've probably seen these two starch molecules represented in large scale as batteries held together with packing tape. Amylose is a long, lanky molecule that stacks up nice and neat when it cools down, causing the congealing of starchy sauces. Amylopectin is more gnarly and tangled, which means it doesn't compact down as much when it cools.
I don't have a source for modified corn starch, but my local Asian food market does sell sticky/sweet/glutinous rice flour, which has about the same amylose to amylopectin ratio. I picked some up and made a basic sasuage gravy for eating with biscuits by replacing the wheat flour called for with the sticky rice flour.
The Good News: The leftover gravy has completely cooled down in my fridge without congealing. Yay science! Also: the Asian market has Ramune.
The Bad News: Sticky rice is just about as close to flavorless as food gets, and it turns out that the wheat flavor is an important component of gravy. I'm guessing this is why Heinz uses modified corn instead rice.
I THINK i might be able to overcome that by mixing a little wheat flour in with the rice flour and taking the roux a level darker since darker rouxs have more flavor, but less thickening ability.
I also occasionally like to melt a wedge of Laughing Cow cheese into my sausage gravy. In the minds of
some people, this makes it technically no longer a gravy, but i think it'll help out with the lack of flavor. Besides, i wasn't planning on sharing my food with them anyway.