Precautions and Tips For Canning Fruits & Vegetables
Canning Fruits & Vegetables
Canning is a way to store products in hermetically sealed and sterilized containers. This is to prevent it from spoiling and make it available in all seasons by increasing its shelf life. Nicolas Appert invented this process, and he is called the father of canning.
Nicolas was a confectioner and chef in Paris from 1784 to 1795. In 1795, he began experimenting with ways to preserve foods, succeeding with soups, vegetables, juices, dairy products, jellies, jams, and syrups. He placed the food in glass jars, sealed them with cork and sealing wax and placed them in boiling water. Nicolas published a book describing his process that year.Nicolas treatise is entitled L’Art de conserver les substances animales et végétales (The Art of Preserving Animal and Vegetable Substances). 200 copies were printed in 1810. This was the first cookbook of its kind on modern food preservation methods. (source)
Canning food was firstly designed for armed forces that were in the war. So by this method, food can be preserved for a long time and transported to the army. Nicolas gave some rules to preserve food by using canning.
First, tightly seal food in containers or jars, heat the container at a specific temperature for a particular duration of time, and maintain it. Then these containers can be used for a long time.
Fruits, vegetables, dairy products, processed food items, and meat can be store in cans. Still, soft drinks can be stored in aluminum tin cans, which are better and not get rust in any environment and have lighter weight.
Canned food preserves all nutrients like vitamins, minerals, carbohydrates, and proteins. These nutrients are not lost during processing and will retain in products until its expiry. While minerals and vitamins mix up into brine or syrup, they can not lose their nutritional values.
Principle of Canning
Many microorganisms can not be seen with the naked eye present on food, and food processing equipment can spoilage. So high temperature is used to destroy these microbes. All particles of food subjected to canning should keep at a specific high temperature for a period of time.
Temperature varies for every food commodity. The primary purpose of using this heat is to kill bacteria, which cause spoilage in food items. If canned products are not processed well, then these can be attacked by bacteria. A pressure canner can be used to low can acid and nonacid food products, such as fish, meat, poultry, and all vegetables except tomatoes.
Typically 239°F can be used to kill Clostridium botulinum for a specific time duration. This bacterium requires high temperature because it remains active at 212°F. This higher temperature can be maintained by using a pressure canner.
For fruits, canning syrup must be used in which sugar concentration is increased. This will impart specific flavor to the product and act as a preservative to prevent food from bacterial attack. Fruits must be blanched before processing in a can. The primary purpose of blanching is to loosen the fruit’s skin. It will retain the color of fruits and vegetables and slow down the activity to enzymes that ripen the fruits.
For canning fruits and vegetables, the same method is used, but process requirements are different.
All meat items like mutton, chicken, beef, and fish are low acidic food like vegetables, requiring similar vegetables. But in meat processing, high temperature is used. This canned meat does not require any other cooking process before consumption. Before processing, cut meat in a small portion of minced it and remove all inedible viscera from meat. Cutting will increase the surface area for a quick process.
When there is a need to store products for a long time, it’s essential to make the environment reproachful for all microbes. Bacteria can not grow in the absence of oxygen, so containers are tightly sealed. The time required for canning depends upon the size of food, type of food items, acidity of the commodity, microorganisms nature, liquid to solid ratio, shape and size of cans, starch concentration, packing tightness, and temperature to prepare food for canning.
Using Vegetable Juice to Preserve Vegetables
These vegetables should properly be sliced sterilized without or with liquid. These types of vegetables need less time for processing and maintain their nutritional values. Sauces type vegetables can be processed in their own juice without adding any brine solution, such as tomato, which is most commonly used.
Using Brine to Preserve Vegetables
A brine solution is mostly used for the canning of vegetables. Salt concentration id higher in a brine solution, salt is added to improve flavor and texture. A high quantity of salt also makes the environment unfavorable for microorganisms. It will increase carbon dioxide concentration and decrease oxygen concentration.
So microbes can not live in the absence of oxygen, and food becomes safe for a more extended period. The most common example of brine is to preserve olives and also add herbs and spices to improve the taste. Its preservation also depends upon the processing time and temperature during canning.
Choosing Vegetables to Can
Freshly harvested vegetables are selected for canning, free from any contaminant, disease, or damage. All inedible portion and damage part should remove from the vegetables, and bruising and blemishing apply to remove dust particles and those extra things that can affect the commodity’s quality. Vegetables should not be wasted while filling in can jar, so avoid overfilling cans, minimizing the food loss.
Leafy vegetables are not recommended to can at the local level. These vegetables are Brussels, cauliflower, wild mushrooms, cabbage, pumpkins, broccoli, and squash, etc. Heat penetration in food is significant for obtaining good quality food. It depends upon the size and content of the jar.
Salt is an optional ingredient. It can use in canned products to increase flavor. It can also make water unavailable for microorganisms for their activity. So by using salt, conditions become unfavorable for bacteria, and food can be store for an extended period. Salt can be omitted in low acid food. Before processing, herbs and spices can be used in a small amount to increase flavor.
Any kind of fat or butter should not use in canned products instead of fat used in the recipe. When butter or fat use in canned products, it will reduce the heat capacity to penetrate food particles. Starchy ingredients should not add in food recipes because this starch absorbs extra moisture and will thicken the canned material during processing. For this purpose, barley, rice, and pasta can not add during canning.
Jars Used for Canning
Jars that are used for canning should be free of any crack and chips. Mayonnaise jars should not be recycled in pressure canners to avoid breakage. In pressure canners, jars should not need to sterilize. The length of the cans should be 946 millilitres.
Raw vegetables or it can preheat or fully hot vegetables be canned except a few vegetables. When hot packing is used, it will produce products of higher quality. And it will remove extra air in containers. The head-space should be one inch, and high pressure should increase to enhance the products’ shelf life.
When liquid added in can jars, then spatula type material is used to remove air space between food particles. Air space and air bubbles should be minimum to increase the quality of the product
Carefully select lids that are correctly fit on to the jar and new cans should be used for good results. Preheating is required for metal lids, and rings can be reused if they are present in good form. If the rings are needed again, then wash them thoroughly, dry, and keep these rings in good condition to be used for many years.
Sealing of Cans
Threads and rim of cans should be clean carefully by using a wet and clean cloth. It will decrease the chances of contamination and give a high-quality product. Then place the lid on the jar and screw on rings and not tighten the jar. It will increase the chance of breakage during any processing step by tightening the lid vent, not correctly.
Canning Jars in Pressure Canners
Hot tap water is put into the pressure canner at the height from 2-3 inches. Still, its quantity can be changed depending upon the processing time. If processing time is 60 minutes or more, then one or two inches of water is added. If pressure canners are deep, then two layers of cans should be used.
Venting Canning Jars
For venting, place canners at high temperatures. Extra air should remove before processing through steam. It is called venting. Venting time is 10 minutes before closing cans. The drawback of this steam, which is released through a vent, is that it will not allow the temperature to be high in products and increase bacterial spoilage risk. Higher pressure is also used to improve the quality and shelf life of food. Processing time and temperature vary for all vegetables according to their nature.
When processing jar filling and sealing is done, the jar should not move from the canners to keep them in canners for cooling and turn off the heat. Keep it in that canner for 15 minutes to decrease its temperature and do not put them on a cold surface abruptly. It will break the jars.
This process of cooling jars takes 45 minutes or one hour in the case of large jars. When this step is completed, then open the vent pipe before removing the lid of canners. This will escape extra steam. Then open the lid in the way that excess can not harm the operators.
Storing Canned Food
All jars from the canners remove by using a can lifter carefully. Then place these jars onto the surface of clothes or any dry place. Do not put it in a cool place.
To test that the jars are correctly positioned in canners, check bubbles quantity in jars. If these are normal, it is mean that these jars are correctly sealed under vacuum.
These jars should not place very close to each other there should be specific space between jars to circulate air to cool them. Place all jars for 24 hours to cool correctly, then look at the top of each lid of the jar. Then use a finger to test the jar seal, press the jar lid with finger. If it bent down, it would indicate the seal is good.
If the jar’s liquid is a leak due to any reason and its quantity show low in food, it never means food is unsafe and can not be used. Just don’t try to open the jar’s seal. But if a large amount of syrup or brine is lost, use it in two to three days. Ring bands on jars can be replaced any time and after cooling, place jars in a cold, dark, and dry place.
Reprocessing Canned Food
If jars are not correctly closed, refrigerate it and use it a few days before spoilage. If there is any reason to reprocess the jar, then use a new lid for this purpose. Put all food material from containers to any saucepan and boil it by using heat. Then fill this material in a clean and new jar at elevated temperature and pressure.
Tips and Suggestions for Canning Food
Testing Canning Equipment
There should be a proper system to test all equipment and process for the accuracy and best results. The test should apply to check the pressure over time then check the tightness of the seal.
Follow the Recipe
Always use fresh vegetables and follow the recipe for the best results. There should be a head-space between the product and jars, but there should not any bubble or air space between food particles in the container.
Careful Handling the Canning Jars
Canning jars should be handle carefully during the process that any small mistake can cause jar breakage. Use a jar lifter to pick it and always have a check and balance on the jar’s position below the jar lifter.
In pressure canners, less water is required, but water is used inadequate amount to produce steam in water bath canners. Because this steam is needed to make pressure but doesn’t overfill the canner with water, it will cause a problem.
Nicolas Appert (17 November 1749 – 1 June 1841) was the French inventor of airtight food preservation. Appert, known as the “father of canning“, was a confectioner. Appert described his invention as a way “of conserving all kinds of food substances in containers”.
The student association of the Food Technology education at Wageningen University is called Nicolas Appert. Since 1972 this association has focused on improving the courses related to food technology education and organises several events each year for students and alumni. Currently almost 900 bachelor and master students are members. In 2017 the association celebrated its 11th lustrum.
² Lorna Kring, July 23, 2016.13 Top Tips for Successful Pressure Canning. Preservation Methods.
² Pollution prevention in food canning processes March 2001.Regional Activity Centre for Cleaner Production (RAC/CP). http://www.cema-sa.org.
² C. D. Pizarro 2000. Las aguas residuales en la indústria agroalimentaria (II).Alimentación, equipos y tecnologia.
² USDA Complete Guide to Home Canning. http://www.fcs.uga.edu/pubs/current/FDNS-E-39.html.
² H. Linda. Safe Methods of Canning of Vegetables. The University of California. http://anrcatalog.ucdavis.edu/
² Canning Vegetables Safely. Wisconsin safe food preservation series.
² Revised by Nancy C. Flores and Cindy Schlenker Davies. Home Canning of Vegetables. College of agricultural, consumer, and environmental sciences.