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Canning is a preservation technique that utilizes jars and cans to safely store and preserve food.
Fresh foods are highly susceptible to spoilage because of their high water content. This water can be a breeding ground for a number of microorganisms. Exposure to oxygen, temperature, ph, naturally occurring enzymes, and time also have a huge effect on the life and quality of food. These factors can either facilitate or impede the deterioration. Over our existence as humans we have found ways to extend the life of our food by manipulating these factors and ultimately changing our relationship with food at its foundation. Food preservation has shaped food culture and created the framework for the food industry. Throughout several articles we will go over some food preservation methods, why they work, and how you can utilize them at home.
How it works
The process of canning preserves food by removing oxygen from the water, preventing the growth of microorganisms, destroying enzymes, and creating a vacuum seal. This can be accomplished through 2 methods: using a water bath or using a pressure canner.
Water Bath: During this method canned/jarred foods are completely submerged in boiling water (212 °F) for a set amount of time which is predetermined.
Pressure Canner: This method utilizes a special pressure cooker in order to raise temperatures past the initial point of boiling to a temperature of at least 240°F. Cans and jars of food are submerged in water inside of the pressure cooker and allowed to cook for a set amount of time.
The main concern with canned food surrounds the microorganism Clostridium botulinum. Most commonly known for causing Botulism; a life threatening disease that comes from ingesting the spores released by this bacteria. Unlike other microorganisms that thrive off of their access to oxygen. C. botulinum grows favorably in a low oxygen environment, making canned goods and sealed containers a safe haven for their deadly toxins. However, C.botulinum cannot grow under a pH of 4.6 making pH an extremely important factor to be aware of when canning.
Altitude is also an area of concern because water boils at different temperatures depending on the altitude. Additional time is needed to process foods at lower boiling temperatures to prevent food from spoiling.
High acidic foods are okay to can using a water bath method. Their low pH in combination with a temperature of 212 °F will take care of any sketchy microorganisms and spores. Low acidic foods have a pH above 4.6, are a concern for C.botulinum, and need to be processed using pressure canning to obtain a higher temperature and ensure safe preservation. Food with a pH close to 4.6 should have their pH lowered by adding an acid like lemon juice and can then be preserved using a water bath method.
Foods safe for water bath: Fruit, pickles, preserve, jam, jelly
Foods with pH close to 4.6: tomatoes, figs
Foods for pressure canning: Meat, poultry, seafood, vegetables, dairy
There are a number of recipes that can be found for all of your favorite fresh foods across the internet. The technique may vary based on the food you are canning but the foundation and the things you need to be aware of is always the same:
Keys to canning
To access information about processing times, canning methods, recommended equipment, recipes, and all you need to know about canning take a look at the USDA complete guide to home canning. https://nchfp.uga.edu/publications/publications_usda.html
Find altitude https://earth.google.com/web/
Follow these tips to keep yourself healthy and keep your food longer.
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We are two food scientists that are all about changing the way we look at our food. We will be diving into all of the research, tips, and tricks on how we can all live a sustainable lifestyle. Join us as we find the most creative and green solutions to saving our food, our bodies, and the environment.