Home Canning: How Canning Preserves Foods1




Click here for printer-friendly pdf version

United States Department Of Agriculture, Extension Service2

The high percentage of water in most fresh foods makes them very perishable. They spoil or lose their quality for several reasons:

  • growth of undesirable microorganisms- bacteria, molds, and yeasts,
  • activity of food enzymes,
  • reactions with oxygen,
  • moisture loss.
Microorganisms live and multiply quickly on the surfaces of fresh food and on the inside of bruised, insect-damaged, and diseased food. Oxygen and enzymes are present throughout fresh food tissues.

Proper canning practices include:

  • carefully selecting and washing fresh food,
  • peeling some fresh foods,
  • hot packing many foods,
  • adding acids (lemon juice or vinegar) to some foods,
  • using acceptable jars and self-sealing lids,
  • processing jars in a boiling-water or pressure canner for the correct period of time.
Collectively, these practices remove oxygen; destroy enzymes; prevent the growth of undesirable bacteria, yeasts, and molds; and help form a high vacuum in jars. Good vacuums form tight seals which keep liquid in and air and microorganisms out.

Footnotes

1. This document is Fact Sheet FCS 8252, a series of the Department of Family, Youth and Community Sciences, Florida Cooperative Extension Service, Institute of Food and Agricultural Sciences, University of Florida. Publication date: June 1998. First published: January 1993. Reviewed: June 1998. This document was extracted from the "Complete Guide to Home Canning", Agriculture Information Bulletin No. 539, USDA. It was originally published on CD-ROM as part of HE 8147, Guide 1: Complete Guide to Home Canning. Please visit our EDIS Web site at http://edis.ifas.ufl.edu

2. Reviewed for use in Florida by Mark L. Tamplin, associate professor, Food Safety, Department of Family, Youth and Community Sciences, Cooperative Extension Service, Institute of Food and Agricultural Sciences, Institute of Food and Agricultural Sciences, University of Florida, Gainesville FL 32611.

The Institute of Food and Agricultural Sciences is an equal opportunity/affirmative action employer authorized to provide research, educational information and other services only to individuals and institutions that function without regard to race color, sex, age, handicap, or national origin. For information on obtaining other extension publications, contact your county Cooperative Extension Service office.

Florida Cooperative Extension Service / Institute of Food and Agricultural Sciences / University of Florida / Christine Taylor Waddill, Dean

Copyright Information

This document is copyrighted by the University of Florida, Institute of Food and Agricultural Sciences (UF/IFAS) for the people of the State of Florida. UF/IFAS retains all rights under all conventions, but permits free reproduction by all agents and offices of the Cooperative Extension Service and the people of the State of Florida. Permission is granted to others to use these materials in part or in full for educational purposes, provided that full credit is given to the UF/IFAS, citing the publication, its source, and date of publication.