Armazenamento e preservação de alimentos: Por que é importante e como fazê-lo corretamente
When you think of storing food for later, what comes to mind? Do you imagine wrapping up some leftovers, putting them in the fridge, and calling it a day? If you’re a more advanced practitioner of the art of food storage, you might fill your crisper drawer with veggies and keep a few fruits on the counter to ripen. But what else should you know about how to preserve and store food, and why does it even matter?
Why Proper Food Storage Matters
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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 (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. Even if you just bought it from a grocery store, it may have been just very recently harvested… or not.
- 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 location in your house and what region you live in)
- The type of storage container or packaging the food is stored in, such as glass, plastic, foil, or cloth.
The Pros and Cons of 6 Ways to Store Food
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There are numerous ways to store food, each with their own benefits and downsides. Here are some things to consider, depending on which method you’re using.
1. Canning
Canning can be a cost-effective way to preserve the quality of food at home. 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.
Canned foods also keep their nutritional value longer, though some losses do occur. Approximately 30-50% of vitamins A, C, thiamin, and riboflavin are lost during the heating process, with an additional 5-20% loss of these per year. Less sensitive vitamins remain intact over time and are found in only slightly lower amounts than in fresh food. Vegetables can be pretty hardy if handled and canned quickly and can maintain much of their nutrition. And you don’t necessarily need to do anything with canned foods before eating — you can just enjoy them right out of the container.
Risks & Downsides of Canning
There are also some risks to consider with canning. Home canning requires a sterile environment to prevent contamination. Canned foods also need to be stored at the right temperatures — with air-tight lids — to prevent pathogens like botulism. In other words, don’t rely solely on the instructions in this article. Follow these USDA guidelines and pay attention to cleanliness, timing, and temperature to ensure you’re preserving food and not armies of harmful microbes.
There are a couple of potential downsides to canning as well. Aside from losing some of their flavor and nutrients over the years, additionally, canned preserves, jams, and jellies often use a lot of added sugar in their preservation process, which presents some health concerns.
It’s important to be aware that mold can grow on canned foods, especially on the surfaces of high sugar foods like jams and jellies. Mold can produce toxic compounds called mycotoxins, which may be carcinogenic. Luckily, mold is often colorful and easy to see on canned food surfaces. You can prevent mold through proper heat processing and air-tight sealing practices. It’s a good idea to test the seals of your canning jars before putting them away for storage in the cupboard or garage.
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 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.
Freezing comes with minimal risks, but there are a few things to keep in mind. Everything in the freezer is subject to freezer burn, which happens when air comes in contact with the surface of the food, and it can look like grayish-brown spots. This doesn’t make the food unsafe to eat, but it does make it dry in certain areas. You can cut these areas off when you thaw the food. And while some foods taste very similar after freezing, others go through significant and sometimes not altogether pleasant changes in texture.
And as much as we’d like them to, frozen foods don’t have an infinite shelf life. Foods such as soups and stews, vegetables, and fruits can spoil after a long enough time. To prevent storing foods in the back of your freezer and forgetting about them for three generations (“Hey, isn’t this a piece of grandma and grandpa’s wedding cake?”) and risking spoilage (which I’m guilty of!), write the date on the container in permanent marker and use or toss extremely old specimens on a regular basis. I’d recommend storing more recently frozen foods at the back and choosing to thaw and eat the older items first. This creates a natural rotation and cuts down on eventual food waste.
3. Drying or Dehydration
An excellent preservation method for fruits, vegetables, and herbs. Drying food tends to increase its flavor, costs very little, and makes storage easier by reducing its size.
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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.
However, dehydration does have some drawbacks. While many nutrients remain fairly stable during dehydration, vitamins A, C, and thiamin are sensitive to heat (if produce is blanched or heated in the oven) and air.
Also, electric dehydrators use a lot of energy, which you can avoid by using some of the other home drying methods when possible. Dehydrating food can also take a while — often over ten hours — so be sure you’re prepared to be patient and do some planning ahead if you pursue this method. And preparing foods for drying can take time, too. For example, slicing and coring fruits and spreading them out on a drying rack, all of which may need to be done manually.
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, or a starter culture), preparing and adding brine, and placing everything in an air-tight container in a cold environment.
Fermentation does require some care, as food can go bad during this process if you’re not using fresh veggies or don’t use distilled or purified water. Fermenting also typically uses a lot of salt, as salt helps preserve food by drawing out its water content and preventing bacterial formation. This is a drawback for people. You may want to think of fresh sauerkraut, kimchi, and other salty fermented vegetables as the “salt source” for some meals.
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. However, I always say, “When in doubt, throw it out.” (Or better yet, put it in the compost!)
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? Yum! Some other commonly pickled foods include beets, cauliflower, peppers, cabbage, and even fruits like lemon or mango.
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Pickling preserves food in a high-acid solution, either via a process of natural fermentation or by adding vinegar and salt (and sometimes sugar). It prevents spoilage and extends shelf life. Many combinations of pickled foods also look pretty and make great gifts!
Very few ingredients are needed for home pickling. Really all you need are the fruit or vegetable, a high-acid brine solution (water, vinegar, 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.
Other Things to Keep in Mind with Cold Storage
Maintaining the proper amount of moisture is also important to prevent drying out, wilting, or premature mold. Rather than storing produce right on the counter or shelf, it helps to store them in containers with holes to promote air circulation like baskets, mesh, or paper bags with holes punched in them.
If your fridge has a fan, as most do, it can dry foods out. The produce drawer is typically protected from this effect. Foods stored loose in the fridge, outside of the produce drawer, will dry out if not kept in a bag, container, or otherwise protected from the fan’s drying effect.
Choosing good-looking produce at the store also helps prevent early spoilage. If you’re not going to eat them immediately, don’t buy avocados that are already mushy or bananas that are already spotting. Check your produce to make sure it’s not badly bruised, discolored, punctured or otherwise damaged.
It’s also important to wait to wash produce until you’re ready to preserve, cook, or eat it, as pre-washing it can actually lead to mold formation during storage. Lastly, if you’re growing your own food, make sure you know when it’s at its prime, so you don’t harvest it too early or too late.
Recipes to Try
If you’re new to some of these food preservation methods and interested in giving some of them a shot, here are a couple of great recipes using the techniques above.
Easy Kimchi from Dr. Joe Mercola
Kimchi is an awesome fermented dish popular in Korea. This recipe uses traditional brining and fermentation to create a nutrient- and probiotic-rich end result. We love this recipe so much that you’ll find it in the Food Revolution Family Cookbook.
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Strawberry Chia Jam from Bakerita
This great homemade jam recipe requires only four ingredients (three if you exclude the maple syrup for an unsweetened version), and the process of heating, cooling, and canning to preserve the final product.
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Dill Pickles from The Kitchn
These quick, garlicky dill pickles take 20 minutes to make. And you can adjust this easy recipe to pickle other vegetables too.
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Try New Ways of Preserving Your Food
Nobody likes coming home or opening their fridge to find that the produce they just bought is already going bad or, even worse, no longer edible. If you never want to examine a plate of “meat-cake,” or if you’re looking for new ways to increase the shelf life of fruits and vegetables you enjoy, give some of these food preservation methods a shot. You might just find that knowing how to preserve food helps you save time, money, and reduce waste… and allow you to enjoy a newfound kitchen hobby in the process!
As informações e sugestões contidas neste blog são meramente informativas e não devem substituir consultas com médicos especialistas.
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