In what decade did Louis Pasteur's germ theory provide the scientific explanation for Appert's success?

The 1860s

Although Nicolas Appert perfected the practical technology of canning decades earlier, the underlying scientific principles remained a mystery to him and his contemporaries. It was not until the 1860s that the scientific community, largely through the groundbreaking investigations of Louis Pasteur, finally established the causal link between microorganisms and food spoilage. Pasteur’s work on fermentation and putrefaction demonstrated definitively that the boiling process used by Appert achieved sterilization by killing microscopic life, and that the airtight seal prevented recontamination. Appert achieved the practical result long before the necessary scientific framework existed to explain the chemical and biological processes at work.