Food preservation includes a bunch of methods of processing fresh produce which destroy food micro-organisms (molds, yeasts, bacterias) and enzymes, which would break down and decay food, and can cause foodborne illness. Correct techniques create conditions which allow for safe and nutritious storage of food, to be consumed at a later stage.
There are many food preserving methods, with the commonly used ones being:
Other methods to preserve food include salting, sugaring, using alcohol, making dairy products, smoking, charcuterie, and sott’olio, and more.
The benefits to preserving your own food at home include:
- Make the most of your homegrown harvests, a great way to handle gluts, and extend the season, being able to enjoy your good food at a later date
- Make the most of in season produce, when it is at its peak, and often cheaper
- Know what it is in your food, and have more affordable chemical-free foods
- Cater to food allergies and dietary requirements
- Reduce waste by using up your garden abundance, as well as items that need using up, and in some cases, leftovers
- Save time by creating sauces, relishes, pesto and other items that can quickly added to meals as a flavour base, or to enhance them
- You can swap, share and barter with your preserves too!
The challenges you may face when preserving your own food can be:
- Initial cost and set up
- Time to learn the skills, troubleshoot, as well as the time to prep and process your food
- Using what you preserve
- Concerns about safety
- Finding somewhere to store it all
Whilst it can seem overwhelming to know where to start, here are 5 simple steps to consider:
1. Pick a method
This depends on your budget, the time you have, the space/ storage you have, and even what you grow, or what produce you have available. For the common methods consider what you can preserve, the difficulty level, time requirements, and equipment requirements.
A big factor is what type of preserved food you are most likely to eat (including if you need to cater for allergies/ intolerances). If you never eat dried apricots, but you love Apricot Chicken, then consider learning how to bottle your own jars of apricot chutney to use as a meal-base! If you want to start making your own breakfast cereal, trail mix and kids snacks, then having dried fruit might make sense.
Of course, there is no reason why you can’t learn all the preserving methods, I just think it is a good idea to start and practice with one method to become more skilled and confident, before moving on to learn others!
2. Find, buy or borrow the equipment
What do you need for the method you have chosen (see next section)? Do you have a friend who you can borrow from? Are there local classifieds where you can source second hand items cheaply? Do you have suitable things in your house already?
3. Borrow or buy a book
Check out my favourite preserving books, and website recommendations below in References and Resources section. Maybe check out your local library, or ask a friend. Also refer to recipes in the instruction manual (download one or contact the company if your item came without one), which often have recipes too.
4. Pick a recipe
Choose a simple recipe from a reliable source of tested recipes, and make it a few times, before moving on to another recipe which uses the same method. See my References and Resources section below for recommendations on reliable sources.
5. ASK QUESTIONS & GET SUPPORT
Join the Growing Home Community, so you have likeminded, experienced people to ask your questions that you just can’t find answers to in books or by Googling (AND so you can show off your successes too!)
Learning the various methods to preserve food, does take time, and commitment to gain new skills and knowledge. You can start with dehydrating or boiling water bathing of high acid produce, which are easier to learn and more ‘fool-proof’. When you feel confident, or have time, move on to learning another preserving method. Once you practice and get more efficient at each method, it won’t take as long each time you do a batch.
To ensure we can preserve safely, let’s understand how food spoilage and food borne illness can occur. There are many microorganisms (bacteria, yeasts, moulds), as well as chemicals like enzymes, which can cause food spoilage. There are also microorganisms which can cause foodborne illness, such as certain bacterias. They generally thrive in conditions which have oxygen, moisture, pH above 4.6 (more alkaline), and temperature between 5 and 60 degrees Celsius.
The aim of food preserving is to destroy these food spoiling and foodborne illness microorganisms, by creating and maintaining conditions they cannot survive in, such as:
- altering the pH by making it more acidic (below 4.6)
- removal of moisture
- very high temperatures, or very low temperatures
- anaerobic (little to no oxygen)
One of the most serious foodborne illness microorganisms is Clostridium botulinum, a soil-borne bacteria which produces toxins that can cause botulism, a potentially fatal paralytic illness. To ensure C.Botulinum spores cannot survive or grow when preserving, we need to use high acid foods/ environments (pH less than 4.6), or for low acid foods, we need to bottle/can using a pressure canner to achieve 116’C. If dehydrating, dry to fully dry & crisp, or acidify before drying (with lemon juice or vinegar). If using the sott’olio method, acidify low acid foods, before submerging under oil, and then store below 4’C. Read more regarding safety for this method here, CSIRO Vegetable Preservation.
Please also consider if you need to adjust your processing times, or pressure, depending on the altitude you live at. If you live more than 305m (1,000 feet) above sea level, the temperature at which water boils gets lower (i.e. your boiling water may not indicate 100’C has been reached). For example, Canberra is 577m above sea level, which is approximately 1893ft. Use these charts to make adjustments for your times or pressure.
An important aspect of food preserving science to understand, is the pH of food. Simply put, high acid foods are safer to preserve, as most food spoiling and foodborne illness microorganisms do not survive in high acid environments. Low acid foods, however, can harbor serious foodborne illness microorganisms, and that is why low acid foods require extra attention.
Foods naturally high in acid, or where a highly acidic environment has been created (pH lower than 4.6), can inhibit the survival and growth of food spoiling microorganisms and their spores (including C.Botulinum) when preserving food.
In regards to bottling (or ‘canning’) foods in glass jars, high acid foods can be processed safely in jars by the ‘boiling water bath’ process (following correct methods and recipes) as temperatures of 100’C will kill the varieties of microorganisms found in high-acid foods. They can also be processed in a Fowlers Vacola preserving unit, as well as dehydrating, freezing and fermenting.
Low acid foods being bottled, must be processed in a pressure canner.
The pH is based on all the ingredients in a jar or product, so whilst you have a zesty, acidic tomato salsa made from tomatoes, lime juice and spices, if you add low acid capsicum, chillies and corn, you may have altered the pH level to be ‘low acid’ and therefore not be acidic enough to safely process in a boiling water bath. The salsa would require pressure canning.
Unless you have pH testing equipment, and skills/ knowledge, to be able to precisely test your preserves, the best advice is to use recipes that have been tested by food preserving experts, and stick to the ingredients, volumes and processing times listed.
Some methods which people use to preserve food at home, may not be considered safe by modern food safety authorities (such as National Centre for Home Food Preservation, USA) who have conducted research and testing in the last 20 to 30 years. Unsafe methods include the ‘open kettle method’ and inversion techniques, using sealing wax or preserving cellophane seals, and bottling/ canning ‘low acid’ foods in a Fowlers Vacola or boiling water bath.
The ‘open kettle’ method is a technique, which involves putting hot contents into hot jars, and putting the lid on (or use wax/ cellophane as the sealant), without any further processing. Some people also turn their jars upside down at that point, called inversion method . Often a vacuum seal is obtained as the jars cool down, but the temperatures obtained in open kettle canning are not high enough to destroy all spoilage and food poisoning organisms that may be in the food. Also, microorganisms can enter the food when it is transferred from the pot/ kettle to the jar, and cause spoilage.
In terms of doing low acid items (vegetables, stock, meat, meals) in boiling water bathing, all food safety and preserving authorities state that is unsafe. You must do low acid preserving in a proper pressure canner (not a pressure cooker) because it reaches the higher temperatures required.
