K-State Research and Extension

There are several reasons cloudiness can occur.

1. The beans may be too mature which makes them too starchy.  The starch settles out of the food during canning. This is a quality issue.
2. Minerals in hard water can give a cloudy appearance. This is a quality issue.
3. Using table salt instead of canning salt.  Table salt contains anti-caking agents that can cause cloudiness.  This is a quality issue.
4. Finally, it could be spoilage due to improper heat processing.  Do not consume them in this case. Plain green beans MUST be pressure canned because they are a low acid vegetable. When not processed properly, Clostridium botulinum could cause foodborne illness.

Learn how to safely preserve green beans in Preserve it Fresh, Preserve it Safe: Beans.

Source: https://nchfp.uga.edu/how/can/general-information/causes-and-possible-solutions-for-problems-with-canned-food