Canning foods needs to be safe
Sunday, August 04, 2013 10:00 PM
I am writing to day to introduce you an online resource for safe canning and preservation of foods. Updates to processes and procedures have been made to ensure safer food practices as we have come to a better understanding of how food is contaminated, how best to prevent this from occurring. I am introducing the National Center for Home Food Preservation. This site is described below in detail. All information is research based and provides information in an understandable way for home food preservers. I encourage you to make use of this valuable information as well as call Joy at the Montgomery County Purdue Extension Office at 364-6363. I am happy to answer your food safety questions related to everyday storage and preparation as well as food preservation methods.
Joy Dugan is the Consumer and Family Sciences Purdue Extension Educator for Montgomery County. She has a Bachelor of Science in Consumer and Family Sciences Education with a Master of Science in Curriculum and Instruction with a specialty area of Consumer and Family Sciences and Extension Education.
We also would like to invite you out to our Home Food Preservation Workshop on Aug. 27 at from 6 p.m. to 8 p.m. We will be covering two types of canning practices: boiling water bath and pressure canners. We will have a short presentation and discussion of the recommendations for each method. We will then experience canning procedure and processes through a hands-on demonstration. Long time canners may attend to get up dated information, as well as new canners to test out if they would like to begin this food preservation process for their families.
Online Resource: National Center for Home Food Preservation
The National Center for Home Food Preservation is your source for current research-based recommendations for most methods of home food preservation. The Center was established with funding from the Cooperative State Research, Education and Extension Service, U.S. Department of Agriculture (CSREES-USDA) to address food safety concerns for those who practice and teach home food preservation and processing methods.
Home food preservation remains an important and popular cultural activity. It is critical that those who practice preserving and processing foods at home have access to the most reliable information available concerning food safety and food quality. The Cooperative Extension System (CES) and USDA have long been recognized as credible sources for science-based recommendations. However, developmental work on new or continued recommendations has been sporadic since the 1950s due to availability of resources and probably interested persons. Two national surveys conducted by the Center in 2000 and 2005 both revealed a high percentage of home food processors are using practices that put them at high risk for foodborne illness and/or economic losses due to food spoilage.
The National Center for Home Food Processing and Preservation was established with funding from the Cooperative State Research, Education and Extension Service (CSREES-USDA) in 2000 as a multi-institutional effort with The University of Georgia and Alabama A&M University as the primary institutions. Expert scientists in home food preservation from industry and eight other U.S. universities comprised an advisory committee for the Center. Home food preservation recommendations were updated through laboratory development and testing of products and critical literature reviews; recommendations from USDA and the Cooperative Extension System have been made available through this website; a new video series; on online self-study course; revision of the USDA Complete Guide to Home Canning (December 2009); updating of Extension professionals in various states; and, various other publications on the website.
The first project ended in 2005, but the Center received additional funding to conduct some additional limited projects through August 2010. Collaborators from 5 states were part of the National Center team for those years, but primarily through 2008. In 2005-2010, work continued on the website-based self-study course modules; applied laboratory research on refrigerator dill pickles and canned tomato-based salsas was conducted; and, an undergraduate college short-course about home food preservation was developed, implemented and evaluated.
The current project, 2011-2014, will be developing, implementing and evaluating a series of six youth lesson plans on home food preservation; developing and teaching webinars on home food preservation; and, building website resources and maintaining the integrity of current website content. In addition, research will be conducted on atmospheric steam canning for acid foods and to compare several home canning lid systems on features of sealing rates and vacuums obtained.
This material is based upon work supported by the National Institute of Food and Agriculture, U.S. Department of Agriculture, under Agreement No. 2011-51110-30995.
This work has also been supported by the Cooperative State Research, Education, and Extension Service, U.S. Department of Agriculture, under Agreements No. 00-51110-9762 and 2005-51110-03283.
General Canning Information
How Canning Preserves Foods
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,
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.
This document was extracted from the "Complete Guide to Home Canning," Agriculture Information Bulletin No. 539, USDA (Revised 2009).
Ensuring Safe Canned Foods
Growth of the bacterium Clostridium botulinum in canned food may cause botulism-a deadly form of food poisoning. These bacteria exist either as spores or as vegetative cells. The spores, which are comparable to plant seeds, can survive harmlessly in soil and water for many years. When ideal conditions exist for growth, the spores produce vegetative cells which multiply rapidly and may produce a deadly toxin within 3 to 4 days of growth in an environment consisting of:
a moist, low-acid food
a temperature between 40° and 120°F
less than 2 percent oxygen
Botulinum spores are on most fresh food surfaces. Because they grow only in the absence of air, they are harmless on fresh foods.
Most bacteria, yeasts, and molds are difficult to remove from food surfaces. Washing fresh food reduces their numbers only slightly. Peeling root crops, underground stem crops, and tomatoes reduces their numbers greatly. Blanching also helps, but the vital controls are the method of canning and making sure the recommended research-based process times found in the USDA's Complete Guide to Home Canning are used.
The processing times in this book ensure destruction of the largest expected number of heat-resistant microorganisms in home-canned foods. Properly sterilized canned food will be free of spoilage if lids seal and jars are stored below 95°F. Storing jars at 50° to 70°F enhances retention of quality.
Food acidity and processing methods
Whether food should be processed in a pressure canner or boiling-water canner to control botulinum bacteria depends on the acidity of the food. Acidity may be natural, as in most fruits, or added, as in pickled food. Low-acid canned foods are not acidic enough to prevent the growth of these bacteria. Acid foods contain enough acid to block their growth, or destroy them more rapidly when heated. The term "pH" is a measure of acidity; the lower its value, the more acid the food. The acidity level in foods can be increased by adding lemon juice, citric acid, or vinegar.
Low-acid foods have pH values higher than 4.6. They include red meats, seafood, poultry, milk, and all fresh vegetables except for most tomatoes. Most mixtures of low-acid and acid foods also have pH values above 4.6 unless their recipes include enough lemon juice, citric acid, or vinegar to make them acid foods. Acid foods have a pH of 4.6 or lower. They include fruits, pickles, sauerkraut, jams, jellies, marmalades, and fruit butters.
Although tomatoes usually are considered an acid food, some are now known to have pH values slightly above 4.6. Figs also have pH values slightly above 4.6. Therefore, if they are to be canned as acid foods, these products must be acidified to a pH of 4.6 or lower with lemon juice or citric acid. Properly acidified tomatoes and figs are acid foods and can be safely processed in a boiling-water canner.
Botulinum spores are very hard to destroy at boiling-water temperatures; the higher the canner temperature, the more easily they are destroyed. Therefore, all low-acid foods should be sterilized at temperatures of 240° to 250°F, attainable with pressure canners operated at 10 to 15 PSIG. PSIG means pounds per square inch of pressure as measured by gauge. The more familiar "PSI" designation is used hereafter in this publication (the Complete Guide to Home Canning). At temperatures of 240° to 250°F, the time needed to destroy bacteria in low-acid canned food ranges from 20 to 100 minutes.
The exact time depends on the kind of food being canned, the way it is packed into jars, and the size of jars. The time needed to safely process low-acid foods in a boiling-water canner ranges from 7 to 11 hours; the time needed to process acid foods in boiling water varies from 5 to 85 minutes.
Process adjustments at high altitudes
Using the process time for canning food at sea level may result in spoilage if you live at altitudes of 1,000 feet or more. Water boils at lower temperatures as altitude increases. Lower boiling temperatures are less effective for killing bacteria. Increasing the process time or canner pressure compensates for lower boiling temperatures. Therefore, when you use the Complete Guide to Home Canning, select the proper processing time or canner pressure for the altitude where you live. If you do not know the altitude, contact your local county Extension Office (765-364-6363). An alternative source of information would be the local district conservationist with the Soil Conservation Service.
As you plan to preserve all that is nature's bounty I encourage you to choose recipes, and methods that ensure the best quality and safest product for your family. Please join us on August 27th to learn more. Call Joy at the Montgomery County Purdue Extension Office to reserve your spot today! 765-364-6363