I canned seven quarts of home grown potatoes last week, and two of the jars contain this white, fibrous material that you can see in the picture. It's not a liquid or gel, so I don't know if it's just starch. I opened one jar today and felt the substance; it's stringy but soft. Is this normal and safe to eat? I've been canning my potatoes for years and never saw this before.

Carolyn,

The "fibers" you're seeing are likely that starch that has leached out of the potatoes during the canning process, either as a result of insufficient soaking in the first step, or during the boiling step when hot packing. However, if the substance appears in only one or two jars, it's possible that something went unnoticed in those jars during packing.

As a general rule, we advise: when in doubt, throw it out. However, if you followed the recommended processing time - 40 min at 11 pounds of pressure for a dial gauge canner, or 10 pounds for a weighted gauge canner - and your lids have sealed properly, your product should be shelf-stable.