I'm trying to make a guava filling similar in consistency to that of lemon meringue pie. I've been thickening with various amounts of cornstarch, but my filling either ends up too runny or too lumpy.
I start by boiling 1.5 c. juice on medium-high heat. Once it comes to a boil, I turn the heat to low and slowly stir in my cornstarch slurry. Still on low heat, I stir for about a minute until the filling thickens and becomes clear.
I've done this a couple of times with slight variations.
1-Used a slurry of 4 tbsp. cornstarch in 1/3 c. water; added to liquid after it had come down from boiling. The result was smooth but too runny.
2-Used a slurry of 4 1/3 tbsp. cornstarch in 1/4 c. water; added to liquid while still boiling (eventually came down with stirring on low heat.) The result was a thicker but lumpy.
After reading this post (http://chowhound.chow.com/topics/714287), I feel like I'm either heating the mixture at the wrong temperature (too hot), adding the slurry at the wrong time/temperature, or using the wrong cornstarch to water ratio, but I'm still uncertain.
I'm hoping someone can point me in the right direction. Thanks.