How to preserve spinach

In this brief guide, we will answer the question “How to preserve spinach” and discuss the different methods used to preserve spinach.

How to preserve spinach

The cool winters and mild summers make coastal California ideal for spinach production, where nearly 65% of the total U.S. spinach is produced (1).

Spinach is preserved by:

  • Refrigerating whole leaves
  • Freezing 
  • Dehydrating 
  • Canning

How to preserve spinach by refrigerating

Whole spinach leaves can be refrigerated for about 6-8 days (2)2 weeks. Refrigerating is the easiest way to preserve spinach, and the flavor and texture are retained throughout. In a study, fresh-cut spinach was treated with citric acid and ascorbic acid solutions and packaged in mono-oriented polypropylene (OPP) bags or low-density polyethylene (LDPE) bags. Best results were observed when LDPE bags were used to store fresh-cut spinach at 4ºC and 90% HR (2).

To refrigerate spinach:

  • Wash fresh spinach leaves. Pick out any yellow or damaged leaves.
  • Dry with a paper towel or a salad spinner.
  • Place the spinach leaves in a container or a sealable bag.
  • Place a few dampened paper towels on top of the spinach leaves.
  • Seal, label and refrigerate for up to 2 weeks.

How to preserve spinach by freezing

Studies showed that frozen storage of spinach significantly reduced the phenolic compounds and the antioxidants after 6 months of frozen storage. Vitamin C contents of spinach decreased during processing by about 30% and during storage by a further 30% (3).

Spinach can be frozen as whole leaves or as a puree. Freezing whole leaves will retain the quality as well as the nutrient content of spinach. Some freezing methods recommend blanching before freezing and some say it is best to freeze without blanching. In this article, we will look at freezing spinach without blanching. 

Heat treatment in blanching may provoke some losses, but inactivation of oxidative enzymes prevents further losses during slow processing and storage. Microwaving is less destructive than steaming and boiling. Typical commercial blanching conditions are 90–95◦C for a duration of 1–10min, usually  achieved by exposure to hot water or steam followed by rapid cooling procedure (4).

Frozen spinach leaves can be added to any recipe that calls for spinach. Frozen spinach puree is great to add for juices, smoothies and soups that call for spinach.

To freeze whole spinach leaves:

  • Wash fresh spinach leaves. Pick out any yellow or damaged leaves.
  • Dry with a paper towel or a salad spinner.
  • Place the spinach leaves in a ziplock bag and squeeze out as much air as possible.
  • Seal, label and place it in the freezer.

To freeze spinach puree:

  • Wash fresh spinach leaves. Pick out any yellow or damaged leaves.
  • Puree the leaves in a food processor by adding the minimum amount of water needed.
  • Pour the pureed leaves into a ziplock bag, a glass bottle or even an ice cube tray.
  • Freeze for up to 6 months.

Frozen spinach leaves and puree must be used within 6 months. If they need to be stored for more than 6 months, spinach must be blanched before freezing. 

How to preserve spinach by dehydrating

Studies reported that to obtain high-quality dehydrated vegetables, the drying process should allow effective retention of color, flavor, texture, taste and nutritive value (4).

Spinach is not usually dehydrated since it loses flavor when dehydrated. However, dehydrated spinach does retain most of its nutrients so it can be added to juices and smoothies in powdered form. Dehydrated spinach can also be added as flakes to soups and casseroles. Dried vegetables can be stored for 6 months at 60ºF, 3 months at 80ºF.

To dehydrate spinach:

  • Wash fresh spinach leaves. Pick out any yellow or damaged leaves. 
  • Remove the thicker stems as they won’t dry out quickly.
  • Dry with a paper towel or a salad spinner.
  • Arrange the leaves on the tray of the dehydrator with enough space between the leaves.
  • Dehydrate the leaves at 125°F for about 4 – 6 hours.

How to preserve spinach by canning

Canning may improve the extraction of carotenoids from their cellular matrix, therefore resulting in higher levels of thermally processed products. However,excess heat may also lead to degradation (5). Canning is not commonly used to preserve spinach since spinach is water and is a low-acid food. However, if a pressure canner is used, spinach can be canned and stored for a long period. Try not to keep canned foods more than 1 year (6).

To can spinach:

  • Wash fresh spinach leaves. Pick out any yellow or damaged leaves. 
  • Blanch the spinach until they are wilted.
  • Pack the spinach into sterilized jars. Salt can be added on top of the spinach if needed.
  • Add boiling water on top of the spinach and leave about 1-inch headspace.
  • Seal the jars.
  • Process the jars using a pressure canner.
  • Label and store the jars in a cold dry place.

More about canning spinach and using a pressure canner can be found here.

Canned spinach, when properly stored, can last for 3 to 5 years. The spinach will be good to eat as long as there is no off odor, flavor or visible mold growth in the jar.

Health benefits and risks of spinach

Spinach is a nutrient-rich vegetable that can be enjoyed raw or added to dishes such as noodles, casseroles and soups. Spinach can also be sauteed as a side dish and added to smoothies.

Spinach is rich in nutrients such as iron, calcium, magnesium, potassium and vitamins (7). 

Around 49% of the caloric value of spinach comes from the plant proteins. This makes spinach the richest known source of protein of all plant foods. One cup of spinach provides 12% of recommended daily requirements of protein (8).

Health benefits of eating spinach include growth of healthy hair and skin, diabetes management, good bone health, good digestive health, and lower blood pressure.

Studies show that spinach and spinach-derived compounds were shown to improve insulin sensitivity and in turn plasma glucose. Evidence from cell culture experiments support the insulin like and insulin-sensitizing actions of spinach extracts (8).

Spinach has a high content of potassium. A high potassium intake is not recommended for people with kidney issues such as kidney stones.

Spinach also contains vitamin K. People on blood clotting medications such as warfarin must not suddenly increase their vitamin K content since vitamin K has a major role in blood clotting.

Overall consuming spinach has a lot of benefits for everyone and few risks for people with kidney disease or blood clotting. Spinach can be a vital part of a healthy, well-balanced diet.

More on the health benefits of spinach can be found here.

Other FAQs about Spinach that you may be interested in.

How much spinach should you eat?

How to Drain Spinach 

How much spinach should I eat a day?

How much are 2 cups of spinach in grams?

Conclusion

In the brief guide, we answered the question “how to preserve spinach” and discussed the different methods of preserving spinach. We also looked at the health benefits and potential risks of eating spinach.

If you have any questions or comments, please let us know.

References

  1. Kandel, Shyam L., et al. Spinach downy mildew: Advances in our understanding of the disease cycle and prospects for disease management. Plant Dis, 2019, 103, 791-803.
  2. Piagentini, A. M., and D. R. Güemes. Shelf life of fresh-cut spinach as affected by chemical treatment and type of packaging film. Braz J Chem Eng, 2002, 19, 383-389.
  3. Puupponen‐Pimiä, Riitta, et al. Blanching and long‐term freezing affect various bioactive compounds of vegetables in different ways. J Sci Food Agri, 2003, 83, 1389-1402.
  4. Kaur, Amandeep, et al. Effect of dehydration on physicochemical properties of mustard, mint and spinach. J food process preserv, 2008, 32, 103-116.
  5. Rickman, Joy C., Christine M. Bruhn, and Diane M. Barrett. Nutritional comparison of fresh, frozen, and canned fruits and vegetables II. Vitamin A and carotenoids, vitamin E, minerals and fiber. J Sci Food Agri, 2007, 87, 1185-1196.
  6. Rasmussen, J and Driessen, S. Storing canned food. 2021. University of Minnesota.
  7. Roberts, Joseph L., and Régis Moreau. Functional properties of spinach (Spinacia oleracea L.) phytochemicals and bioactives. Food func, 2016, 7, 3337-3353.
  8. Pandya, Spandan. Estimation of Iron and Copper from Spinach Leaves. 2009. Chemistry department, Mithibai College.