In some cases, the sauce may even split or loosen in the fridge, forming a watery layer. If you let a gel cool completely, like a container of cornstarch-thickened sauce in the fridge, you might notice it turns into a firm, opaque block, which is the result of the starch molecules reassociating and falling into a crystalline structure. That reassociation during cooling is called retrogradation. So a pudding thickened with pure amylose might be excessively firm and brittle (like firm jello). Once those molecules reassociate into linear chains, the resulting gel is quite firm. Amylose has a linear structure and is tightly bonded, so it generally takes higher temperatures to break those bonds in order to thicken its surrounding liquid. A mixture thickened with pure amylopectin might be stringy or slimy, despite being the right “thickness.” If our goal is to have a more stable, firmer gel, then we might choose a starch with relatively high amylose content. The tradeoff? The resulting gel doesn’t have as much strength. That’s because the larger, branched structure of amylopectin is better at raising viscosity. For example, if our goal is to thicken a liquid with the addition of some kind of starch, we’d turn to starch sources with a relatively high amylopectin content if we’re looking to maximize thickening power. The relative proportion of amylose to amylopectin in a given starch will dictate its behavior.
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