When canning is done right, it is a very effective way of preserving food. It was invented by a French chef by the name of Nicholas Appert, who discovered that heating food up to a certain temperature and then placing them in containers that are vacuum sealed prevented food spoilage-causing bacteria from proliferating, and thus preserved the food for later consumption.
Canning, when done properly, is a safe way to prolong the shelf life of food. Today, there are three scientifically-approved methods of canning – water bath canning, pressure canning, and steam canning.
How Do I Can Green Beans the Old-Fashioned Way?
As green beans are a low-acid food, the only way to safely can them is to use a pressure canner or a special pot that heats up the jar to temperatures above 240°F. Other canning methods such as water bath canning or steam canning may only be used if you increase the acidity in your green beans, for example, through pickling.
What’s the Best Way to Can My Green Beans?
Canning is such an effective food preservation technique that a lot of home cooks employ it in order to prolong the time that they can enjoy the food at their peak season.
For example, those luscious tomatoes you just got from your garden or from the market that you wish you can have all year long. Canning offers that option for you to save that incredible taste for future, out-of-season cravings.
Green beans are also a warm-weather vegetable that you may want to can so you can enjoy them in the colder months. So what’s the best, easiest method to can them?
Pressure Canning Is the Way to Go
To date, there are only three scientifically-approved, safe methods of canning that people may employ to preserve food —water bath canning, steam canning, and pressure canning.
Where the food sits on the pH scale is the prime determinant of which of the three methods you can use to can your food.
In general, high-acid food, or those with a pH value of less than 4.6, may be canned using all three methods, provided that the recipe used is tried and tested and approved by experts.
Low-acid foods, those with a pH value above 4.6, can only be safely canned using the pressure canning method, which is the method that offers the option for heating the jars to higher temperatures – above 240 °F compared to 212°F for water bath canning and steam canning.
Green beans are considered a low-acid food with a pH of 5.6, and the Natural Center for Home Food Preservation says that the only way to safely can green beans is to use the pressure canning method. Because of the low acidity of the green beans, water canning or steam canning is insufficient.
If you wish to can them using either of these two methods, you need to increase the acidity in your green beans by pickling them.
Pickling green beans using a tested recipe will make them a totally different product, so if this isn’t what you had in mind and you wish to preserve your green beans as is, there is no other choice but pressure canning.
Why is Temperature and Acidity Important in Canning?
Okay so you might wonder, why are high temperatures and acidity so important in this canning business?
The high temperatures and acidity in the food and the canning method are what ensure that the food you preserve will be safe and delicious to eat.
The Role of Temperature
Heating the jars at high temperatures will kill off the harmful bacteria, yeast, mold, and pathogens that are responsible for making the food unsafe to eat.
The higher the temperature it is heated, the more we ensure that these pathogens are neutralized.
According to The Principles of Home Canning Guide by the USDA, warming food at temperatures between 140°F – 160°F prevents the proliferation of bacteria but is not enough to kill all of them.
Going up higher at 212°F, which is the boiling point of water and the maximum temperature for the water bath canning and steam canning methods, these bacteria and pathogens are killed, although the spores of a particular bacteria called Clostridium botulinum do survive even these temperatures. When the spores are activated, they release a dangerous toxin that causes botulism.
In high-acid foods, the survival of these spores are not dangerous because they are neutralized in highly acidic environments. In low-acid foods though such as green beans, this can be very dangerous.
Going up to temperatures of 240°F and above, which is the temperature reached by pressure canning, these spores are effectively neutralized when processed according to the prescribed boiling time.
This is the reason why low-acid foods must only be canned using pressure canning. Water bath canning and steam canning should only be used for foods that have high acidity.
Aside from killing pathogens, the increase in temperature is also responsible for deactivating the enzymes that cause the breakdown in the food, thus preserving it for longer.
The heating process is also what is responsible for creating that sterile environment or vacuum seal in your canned jar.
The Importance of Acidity
As we mentioned earlier, the acidity of the environment inside the jar is very important in ensuring the safety of our canned food. Canning low-acid foods using water bath canning or steam canning is insufficient to make them safe.
They need to be processed at higher temperatures to kill some heat-resistant bacteria and their spores to prevent botulism. The acidity in them is not enough to ward off the release of the dangerous toxin that causes this illness.
High-acid foods like tomatoes and apples, and properly pickled foods are the only ones that may safely be processed through water canning and steam canning.
Do not use untested recipes or follow the advice of just anyone, especially when they tell you that it’s safe to can low-acid foods like green beans using a water bath. Let’s always be careful as it is our health and our life that is at risk.
How To Can Green Beans Using A Pressure Canner
This recipe is from the National Center for Home Food Preservation. It is important to only use recipes that are tried and tested and approved by such authoritative experts on canning.
Canned Green Beans
Yield: 7 Quarts
- 14 pounds Green Beans
- 7 teaspoons Canning Salt (optional)
- Wash and trim your green beans. You can choose to leave them whole or cut them into pieces of about 1-inch.
- Pack the green beans into the jars.
For Raw Packing:
- Fill up your jars with your raw green beans, tightly packed. Make sure to leave a 1-inch headspace above them.
- Add the canning salt if using.
- Cover the beans with boiling water, again leaving 1-inch up top.
For Hot Packing:
- In a pot, boil beans in boiling water for 5 minutes.
- Transfer the beans to the jar, making sure they aren’t tightly packed. Leave 1-inch headspace up top.
- Add the canning salt if using.
- Pour the boiling liquid and leave a 1-inch space on top.
Make sure the lids are secure and process in the pressure canner.
The recommended pressures can be found in this resource.
How Does Canning Work?
Canning is basically placing food in sealed jars and then heating them up to temperatures that kill microorganisms that cause food spoilage and food-borne illnesses.
As the sealed jar is heating, the contents in the jar expand and air escapes. After this heating process, the pressure in the atmosphere outside the jar becomes greater than inside the jar, causing the lid to “pull in” towards it, thus creating a vacuum seal.
This vacuum seal is what keeps new bacteria from coming in to contaminate your food. This sterile environment that is created through this heating process is what preserves the food for a very long time.
What Are the Three Methods of Canning?
There are only three scientifically approved and scientifically deemed safe methods for canning, and they all have precise procedures that must exactly be followed to ensure food safety.
Water Bath Canning
Water bath canning, also known as “hot water canning”, is when loosely sealed jars of high-acid food are submerged in boiling water for a prescribed period of time.
No special equipment is needed for this method, as you only need a big enough stockpot that can hold your jars with about an inch of water above them, taking into consideration that your jars need to be placed on a rack so as not to get their bottoms in contact with the bottom of the pot, and therefore over direct heat.
In this canning method, the food jars are submerged and boiled in 212 °F water for the time prescribed in the recipe.
The temperature cannot ever go above this temperature as this is the maximum temperature at which water boils. This means that no matter how long you boil the food, if it is a low-acid food, it will not neutralize the spores of the pathogens that cause botulism.
This method is only suitable for high-acid foods like jams, jellies, pickles, chutneys, and a lot of fruits like apples, berries, peaches, and plums.
Atmospheric Steam Canning
This type of canning method is an alternative to the water canning method, but instead of submerging the jars in water, it is done in a special pot that uses steam to do the heat processing instead of water.
It is said to be more cost-efficient, energy-efficient, and time-efficient, and won’t cause any unfortunate accidents like the water boiling over.
However, the maximum temperature that it can heat the jars up to is the same as the water canning method, which is 212 °F. This means that this is also only suitable for high-acid products.
This type of canning method is what is recommended for low-acid foods like our green beans. This method entails placing your filled jars in a special pot called a pressure canner and heating them to temperatures above 240°F for the amount of time prescribed in your tried and tested and expert-approved recipe.
The higher temperatures in pressure canning safely kills pathogens and inactivate enzymes that are responsible for food spoilage and food-borne illnesses.
This is the safest and most recommended method for low-acid foods as it is the only method that reaches a high enough a temperature to eliminate food safety risks.
Green beans, corn, broccoli, garlic, mushrooms, peppers, artichokes as well as meat and most vegetables are all low-acid and must be canned only using this method.
How Did They Can Low-Acid Foods Like Green Beans Prior to the Pressure Canner?
I know what you’re thinking. But how did they can green beans and low-acid food prior to the invention of the pressure canner? Surely it was through the water bath method?
The answer to that question is, yes, it was mostly through the water bath method, however, it didn’t mean that it was safe and people didn’t get sick from it.
It wasn’t until the late 1800’s that the germ and bacteria theory came out, so while people were unsafely canning their low-acid food and getting sick from it, they didn’t definitively associate it with the canning method. Also, people didn’t always get sick from it 100% of the time, so it made it even harder to associate the unsafe canning method with the sickness.
It wasn’t until a botulism outbreak in 1919-1920, due to canned olives, that the problem was put in the spotlight.
The National Canners Association and the olive industry basically put together a Botulism Commission made up of scientists to figure out what was happening and it was discovered that spores of the Clostridium botulinum could survive boiling water temperatures and low-acid environments. This was when the pressure canner was basically invented and popularized to avoid this problem.
So yes they did can it unsafely prior to the discovery that it was unsafe, and many people suffered consequences as a result. The advancement of scientific inquiries, however, and the conclusive results that stemmed from it solidified our understanding of how canning works and as a result, canning today is much safer than it was a century ago.
What Other Ways Did People Use To Preserve Food?
Aside from canning, people preserved food through fermentation and through salting, and drying. Countries like China, Japan, Italy and Spain have rich and long histories of these preservation methods, which are deeply ingrained in their cultures to this day.
Frequently Asked Questions to How to Can Green Beans The Old Fashioned Way?
Can I Can My Green Beans in the Oven?
There are only three scientifically approved methods of canning: water bath canning and steam canning for high-acidity foods and pressure canning for both types of foods, but most especially for low-acid foods. Any other method has not been proven to be safe, including canning in the oven.
Can I Add Vinegar to Green Beans To Increase Acidity and Do Water Bath Canning?
The only way to safely can green beans using the water bath method is to pickle them using a tested and proved recipe. Simply adding vinegar to them and proceeding with canning does not guarantee that it will be safe to consume.
Conclusion To How To Can Green Beans the Old Fashioned Way
Green beans, unless they are pickled, can only be safely canned using the pressure canning method.
Other methods such as water bath canning and atmospheric steam canning do not reach high enough temperatures to kill the spores of the bacteria that causes botulism, and low-acid foods like green beans cannot neutralize these toxins the way high-acid foods can.
As such, only high-acid foods are suitable for water bath canning and atmospheric steam canning, and all low-acid foods, unless pickled, must be canned using pressure canning.
Daniel Iseli (Head Chef)
Hi, my name is Daniel and I am passionate about cooking. I have been cooking for the past 20 years and am happy to share my best recipes and cooking-related knowledge with you.