Food Preservation & Storage

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To survive, our ancestors had to find ways to make food last. In frozen climates, they froze meat on the ice. In tropical climates, they dried foods in the sun or fermented produce in sweet or salty brine.

In ancient times, the sun, wind and smoke were used to naturally dry foods. Evidence shows that Middle East and oriental cultures actively dried foods in the hot sun as early as 12,000 B.C. The Romans were particularly fond of dried fruits.

Three Types of Food

All food can be classified into one of three groups, which require different storage methods.

1. Perishable Foods

These include many raw fruits and vegetables as well as, for those who eat them, meat, dairy, and eggs. All cooked foods are considered perishable foods. To store these foods for any length of time, perishable foods need to be held at refrigerator or freezer temperatures. If refrigerated, many perishable foods should be used within 3-7 days and less for many animal products.

2. Semi-perishable Foods

Food that’s semi-perishable — depending on how they’re stored and handled — can go bad quickly, or can have an extended shelf life. Flour, grain products, dried fruits, and dry mixes are considered semi-perishable. If optimally stored and handled, like in a clean, vacuum-sealed bag, semi-perishable foods may remain unspoiled for six months to a year. Frozen, some can last even longer.

3. Staple, or Non-perishable Foods

Dried beans, spices, and canned goods are all non-perishable foods. They won’t spoil unless they’re handled carelessly. However, even if they’re stored under ideal conditions, they can start to lose quality over extended periods of time.

Factors That Affect Food Storage Life 

For perishable and semi-perishable foods, the general rule of thumb is that if you can’t use it promptly, it needs to be stored or preserved.

Here are the main factors that will impact a food’s shelf life during storage:

  • The food itself (for example, strawberries can degrade in as little as a day, while potatoes can last for months when properly stored).
  • The freshness and ripeness of the food when you obtain it. This depends in part on where it was grown and how long it spent in transit.
  • The length of time and the temperature at which it was held before you bought it.
  • The temperature of your food storage areas, whether it’s the refrigerator, freezer, countertop, pantry, or basement.
  • The humidity level in your food storage areas (which can vary greatly depending on the region you live in).
  • The type of storage container or packaging the food is stored in, such as glass, plastic, foil, clay or ceramic vessel or cloth.

There are numerous ways to store food, each with their own benefits and downsides.

1. Canning

Canning can be a cost-effective way to preserve the quality of food. Commonly canned foods include applesauce, vegetables, jams and jellies, and baby purees.

The basic steps for proper canning include thoroughly washing the fresh produce you’ll be using, peeling and hot packing if needed, adding acids like lemon juice or vinegar if the food isn’t already sufficiently acidic, and using self-sealing containers with lids. Canning jars are then processed by boiling water (for acidic fruits and vegetables) or using a pressure canner (for low-acid fruits and vegetables) for the appropriate amount of time. This helps prevent bacterial growth and kill any pathogens to ensure safety.

Home canning can lead to significant financial savings, and it gives you no risk of BPA contamination, as you will use glass mason jars in place of plastic or BPA-lined commercial cans.

2. Freezing

A great option for preserving most foods. You can freeze soups, baby purees, oats, and coffee grounds to veggie burger patties, chopped fruit, and blanched vegetables.

A properly maintained freezer (even antique ice boxes) will store food for long periods, after which you can safely thaw (either in the fridge or by setting in cold water only) and cook it as desired. Nutritionally, foods that you prepare at home and then freeze are almost always better for you than frozen meals you’d find at the grocery store.

3. Drying or Dehydration

An excellent preservation method for fruits, vegetables, and herbs. Drying food tends to increase its flavor, increases potency, costs very little, and makes storage easier by reducing its size.

How does it work? Dehydration removes water from fresh food, which prevents bacterial growth. The moisture content of home-dried food should be around 20% or less. You can do this by using a commercial dehydrator, hanging bunches of fresh herbs to dry (unless you live in a high humidity area), oven drying foods, or even using the sun to make your own solar food dryer. Before you dry certain fruits and vegetables, you may want to blanch them (dip them briefly in boiling water) to help preserve them.

4. Fermentation

Fermenting foods is a great way to boost your intake of healthy probiotics (good bacteria) that are great for your digestive system and immunity. Fermenting starts with lacto-fermentation, which is a bacterial process that preserves and boosts nutrients in food. The basic steps include chopping, grating, or otherwise preparing your raw food, deciding on the culture you’ll use (typically salt, whey), preparing and adding brine, and placing everything in an air-tight container in a cold environment.

For a list of fermented food of the Americas, see Lost & Found: Nutrition Reboot.

A Note About Mold

How do you tell if fermented foods have gone bad? Often, a film may develop on the surface, but this may not necessarily be mold. Sometimes it’s actually a harmless yeast called kahm yeast. Other, sometimes fuzzy spots on your food that are pink, black, green, or red, are mold. This doesn’t mean the whole batch is garbage, though, as you can often remove the top layer and still safely consume what’s underneath the brine — if it smells and tastes okay.

Mold is actually fairly rare in fermented foods, and there are some ways to prevent it from developing. First, use the freshest produce you can, which in an ideal world would be organic from your own garden. Next, choose the appropriate cool temperature for fermentation, between 65-70 degrees Fahrenheit. Also, using the right amount of salt — around 1-3 tablespoons per quart of water — can help prevent mold.

5. Pickling

Similar to fermentation, pickling can be done on more than just cucumbers. Have you ever had pickled green beans? Delicious! Some other commonly pickled foods include beets, cauliflower, peppers, cabbage, cucumbers, carrots, and even fruits like lemon or mango.

Pickling preserves food in a high-acid solution, either via a process of natural fermentation or by adding natural vinegar (fermented apples) and salt (and sometimes sugar). It prevents spoilage and extends shelf life.

Very few ingredients are needed for home pickling. Really all you need are the fruit or vegetable, a high-acid brine solution (water, salt, and optional sugar), and an air-tight container.

6. Cold Storage

This is the most common way many of us store produce, whether in the refrigerator or in an underground root cellar if you’re lucky enough to have one of those. Cold storage produce, like apples, pears, root vegetables, celery, and cabbage can last up to several months if stored correctly.

It’s important to make sure you’re aware of and following ideal temperatures and conditions for food storage to get the best shelf life from them. Apples, for example, should ideally be stored at just above freezing, in a damp and breathable bag.

Even though it’s tempting to bring your fresh produce home and line it all up on the counter, it’s best not to store things closely together as this can cause them to spoil. Many fruits and vegetables, like apples, cantaloupe, blueberries, bananas, potatoes, and tomatoes give off ethylene gas, which makes things around them ripen and brown faster.

Different fruits and veggies need to be stored in particular ways to best preserve their freshness. Some produce like apricots, grapes, strawberries, green onions, and asparagus go in the fridge right away. Avocados, kiwi, peaches, and pears should ripen on the counter before you put them in the fridge. And never refrigerate pomegranates, mandarin oranges, ginger, and jicama, as they fare best at room temperature.

Food Atlas Calculator

In November 2019 The World Research Institute launched the Aqueduct Food initiative. Aqueduct’s aim is to help decision makers map and proactively manage water‐related risks to food production. Aqueduct Food combines global data on water risks and agriculture to illustrate water‐related threats to and opportunities for food security, and how these dynamics may develop over time. WRI’s Aqueduct water risk maps are cross‐referenced with data from the International Food Policy Research Institute (IFPRI) showing spatially explicit global crop area along with data on food production, demand, trade, prices, and hunger for every country in the world. By providing users with a better understanding of how population growth and climate change will affect global food systems, Aqueduct Food aims to enable proactive management of water related risks to food security.

Link to Aqueduct’s Food Atlas Calculator.

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