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Home Preservation Nutrition

Eating a nutritious, balanced diet is one of the top indicators for a healthy life. Nutrient-dense foods including fruits and vegetables are key to making sure you get the right nutrients, but it isn’t always easy to access those foods year-round if you don’t live in the tropics.

 

From canning to pickling, there are a lot of different preservation methods available to improve the longevity of those foods so you can eat them year-round, but not all of those methods really preserve the nutrients and health benefits of the raw food. Today, we’re breaking down some of the nutrition facts about common preservation methods to see the pros and cons of each method and help you determine what approach is best for your foods and preservation needs.

 

CANNING

Canning is a relatively new technique for food preservation, dating back to only 1809. The technique was originally developed to preserve food for the French army and navy and took over a century to be adopted commercially in the U.S.[1]!

 

The heat required for canning poses an increased risk for nutrient loss. Nutrients such as Vitamins C and B6 and thiamin are particularly susceptible to heat exposure and suffer much higher losses during canning. Oxidation, or exposure to air, is another risk inherent in the canning process that can lead to losses of Vitamins A, D3, and C[2] [3].

 

An additional risk posed to the nutrient content of canned foods is post-canning cooking. For instance, cooking canned green beans or other vegetables increases the produce’s exposure to heat, oxygen, and moisture and can cause increased nutrient loss.

 

However, canning does still provide nutritional benefits. Produce is usually canned shortly after harvest, reducing the amount of time for nutritional degradation during transportation, and may increase the concentration of some nutrients such as beta-carotene[4].

 

FERMENTING

Fermentation has been used by humans for almost as long as farming has: some of the earliest records of fermentation date back to the Stone Age[5]! While fermentation is perhaps best known for producing beverages such as beer and wine, it is also an important method of preserving foods such as vegetables, meats, and cheeses.

 

Though intended primarily to make foods more palatable, fermentation successfully preserves high percentages of nutrients within the food. For instance, approximately 95% of the caloric energy is preserved in a food when fermented[6]. Fermentation also improves the digestibility of some foods: plant proteins can be difficult for the human digestive system and cause upset, but fermentation helps increase the digestibility of plant products and reduce the presence of components which may cause digestive upset[7].  

 

However, some of this improvement is due to the degradation and loss of other nutrients. Partial digestion of proteins in the fermentation process may lead to a lower overall protein content, for example.

 

FREEZING

Freezing fresh produce is a popular method of food preservation in part due to its versatility and the lack of a need for extra equipment. In other words, almost any food can be frozen and almost every home has a freezer.

 

Additionally, freezing is largely considered the best option for preserving nutrients in foods. While a decrease in taste is common, frozen foods frequently have as high or higher nutrient contents than their fresh counterparts after transportation[8]. As long as food is frozen quickly, stored in an airtight container, and not subjected to thawing and refreezing, frozen foods provide a high level of nutritional value per serving.

 

Some risks in consuming frozen food have to do with improper preparation or storage. In the first, it’s important to avoid buying or consuming frozen foods that show signs of thawing and refreezing, such as icicle formation. For the second, make sure to keep your frozen products in airtight packaging or containers to prevent freezer burn or other damage. Additionally, while frozen food may be safe to eat long after its recommended storage time, it’s generally best to consume frozen products within 8-12 months[9]. This helps ensure higher food quality, even if it’s still technically safe to eat later on.

 

DEHYDRATION

Dehydration has been practiced for nearly the entirety of human history. From Ancient Egypt to the modern U.S., drying food to prevent microorganism contamination has been an important way of preserving food around the world[10]. By removing water from the food, dehydration reduces the risks of mold, yeast, or bacterial growth.

 

The main risk to nutrients from dehydration is due to heat and light. Depending on the type of dehydrator used, heat may be the only concern while solar dehydrators will introduce both risks. Both of these factors interact differently with vitamins and proteins in food: while heat may reduce the presence of certain vitamins by up to 30%, it has little effect on protein preservation[11]. In particular, Vitamins C, folate, thiamin, and B6 are susceptible to heat while riboflavin is susceptible to light[12].

 

Vitamins A and C are particularly vulnerable to degradation from dehydration, as they are largely destroyed by exposure to heat and air – both of which are necessary in the drying process. While blanching – [what is blanching] – or sulfite treatments can be used to reduce the loss of some vitamins, they result in a loss of vitamin C and B-complex vitamins, as well as thiamin and some minerals[13].

 

On the other hand, nutrients such as essential fatty acids and Vitamins D, E, and K are almost completely preserved through dehydration. This is because they are primarily stored in the dry matter of the food, which protects them from heat, oxidation, and other causes of degradation[14]. Dietary minerals such as copper and iron and most proteins are likewise preserved.

 

There are some ways to reduce nutrient loss in dehydration. Using low heat and a gentle air cycle, nutrient losses can be limited to only 3-5%[15]. These adjustments reflect the designs of solar dehydrators as opposed to electric or oven dehydrators, which utilize higher heat settings and a fan-based air flow.

 

An additional benefit to solar drying is its efficiency: according to a 2011 study of sun, oven, and solar drying, foods dried through solar dehydration had the lowest moisture content, making the products less susceptible to contamination or other degradation[16]. This same study indicated that, with some foods, solar drying caused the lowest nutritional loss of each type of drying.

 

Another important factor in dehydrated foods’ nutritional value is their storage: keeping dehydrated foods in a cool, dry place will prevent nutrient loss after drying and ensure a longer shelf life for the food.

Determining which method is best for you will depend on a few factors: what food you want to preserve, what you want to use the preserved food for, and what equipment you have. If you’re looking to preserve fish to be cooked and added into a stew, then freezing is a good choice. On the other hand, if you want to preserve fresh apricots for a road-trip snack, dehydration will make an easier, healthy choice. Canning and dehydration may require additional appliances or tools while freezing may be most convenient if you already have an in-home freezer.

 

Overall, there is no perfect preservation method but each technique can help ensure you and your family maintain healthy nutrition year-round.


Sources:

[1] https://www.britannica.com/topic/canning-food-processing

[2] http://ucce.ucdavis.edu/files/datastore/234-779.pdf

[3] https://www.dsm.com/markets/anh/en_US/Compendium/vitamin_basics/vitamin_stability.html

[4] https://www.foodsafetymagazine.com/signature-series/smart-food-understanding-the-nutritional-value-of-canned-foods/#References

[5] https://www.ncbi.nlm.nih.gov/pmc/articles/PMC539767/

[6] https://link.springer.com/chapter/10.1007/978-94-011-7030-7_16

[7] https://www.ncbi.nlm.nih.gov/pmc/articles/PMC6261201/

[8] https://www.berkeleywellness.com/healthy-eating/food-safety/article/freezing-food

[9] https://extension.umn.edu/preserving-and-preparing/science-freezing-foods

[10] https://www-taylorfrancis-com.proxy.lib.iastate.edu/books/9780429213816 

[11]https://books.google.com/books?id=myuBeotAJz8C&lpg=PP1&ots=fW_BV6dZNL&dq=dehydrated%20food%20nutrition&lr&pg=PA100#v=onepage&q&f=false

[12] https://books.google.com/books?id=I5XbBwAAQBAJ&lpg=PR11&ots=R-WTp9l0Em&dq=dehydrated%20food%20nutrition&lr&pg=PA7#v=onepage&q&f=false

[13] https://extension2.missouri.edu/gh1562

[14] http://www.ijfe.org/uploadfile/2018/0525/20180525042720542.pdf

[15] https://foodassets.com/info/dehydrated-food-versus.html

[16] https://scialert.net/fulltextmobile/?doi=ajb.2011.458.464


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