Signs that flavors are fully extracted from your simmering stock include bones becoming brittle and easily broken, vegetables turning mushy and losing their distinct flavor, and the stock itself developing a rich, concentrated taste.
When making stock, the goal is to draw out all the desirable flavors from the ingredients into the liquid. Here's how to recognize when that process is complete:
Bones: The bones, particularly those with cartilage and connective tissue, will become noticeably softer. They might even crumble or break easily when pressed. This indicates that the collagen has broken down into gelatin, contributing to the stock's body and richness.
Vegetables: The vegetables, such as carrots, celery, and onions, will become very soft and mushy. They will have lost most of their original color and flavor, indicating that their soluble compounds have been released into the stock. They may even start to disintegrate.
Flavor: The stock itself will have a deep, complex, and concentrated flavor. It should taste rich and savory, with a noticeable depth that wasn't present at the beginning of the simmering process. Taste the stock periodically to monitor its flavor development.
Appearance: The stock may become slightly cloudy or opaque as proteins and other compounds are extracted from the ingredients. This is normal and contributes to the stock's body.
Avoid over-simmering the stock once the flavors are fully extracted. Prolonged simmering beyond this point can lead to a bitter or muddy flavor as undesirable compounds are released from the ingredients. Strain the stock promptly once it reaches its peak flavor.