Cooling Considerations for Spinach Post-Harvest

Spinach is practically the embodiment of healthy eating in the US. It can be found in abundance in salads, soups, and other dishes, particularly “Florentine” recipes. Spinach’s reputation for health and nutrition isn’t all hype either; it contains bountiful amounts of vitamins A, C, and K, as well as iron, magnesium, folate, and manganese. However, for spinach to both taste its best and pack the most nutritional punch it is imperative that the spinach be as fresh as possible. Proper cooling and storage techniques are a must for spinach.

General Facts About Spinach

For most of its taxonomic existence spinach was classified as a member of the Chenopodiaceae family. However, in 2003 that family was merged with the Amaranthaceae family, with the amaranths retaining the family name. Historically spinach is believed to have first developed in Persia and from there spread into India and eventually China, where it was first recorded in written history in about the seventh century AD. Eventually spinach became popular throughout the Mediterranean region and eventually spread across Europe. Catherine de’ Medici, queen of France in 1533, was so fond of spinach that she decreed that it be served at every meal. Because Catherine originally came from Florence, dishes made with spinach became known as “Florentine,” a term still popular today.

Over the centuries spinach has been cultivated to enhance a number of desirable traits. Modern spinach grows more rapidly but takes longer to seed. It is also larger and has a less bitter taste. The three main types of spinach include the Savoy, Semi-Savoy, and Flat. Each type has many different varieties and cultivars.

Spinach has long been famed for its high iron content, and indeed it does have 21% of the daily recommended value. However, an error by a German scientist in 1870 incorrectly reported that spinach has ten times the amount of iron that it actually contains. The error occurred as the result of a misplaced decimal point. This in turn led to a misconception about the true iron content of spinach.

General Information About Cooling and Storing Spinach

Regardless of the nutrient being studied, it has been well documented that spinach loses much of its nutritional value as it ages. This makes it even more important for it to be kept as fresh as possible and to be properly cooled and stored. Improperly handled spinach may also harbor dangerous bacteria. The following cooling and storage considerations should be kept in mind:

Temperature – Spinach should be stored at about 32°F to slow down the decay process. Warmer temperatures are insufficient while colder temperatures run the risk of accidental freeze damage. Spinach may intentionally and successfully be frozen for longer-term use.

Relative Humidity – Spinach requires a high relative humidity of about 95% to 100% to prevent it from drying out.

Storage & Handling – Spinach is very delicate and can easily be damaged by careless handling. When left loose care should be taken to ensure that it is adequately ventilated during cooling. For added protection and cooling efficiency it is often stored in perforated plastic bags.

Shelf Life – Fresh spinach has a shelf life of about 10-14 days. Frozen spinach may last up to eight months. Canned spinach can last even longer with shelf life determined by various conditions.

Methods of Cooling Spinach

Hydrocooling – Spinach is often pre-cooled using hydrocooling, which involves rapidly submerging the leaves in near-freezing water. This is a very effective means of quickly removing field heat so that additional cooling and storage methods can then be performed. Hydrocooling requires too large a cooling load at lower temperatures to be viable as a total cooling method.

Forced-Air Cooling – After precooling, spinach may attain long-term storage temperatures through the use of forced-air cooling. Forced-air cooling involves placing the produce in a chilled room such as a cooler, and then pulling cold air past the leaves, thereby forcing airflow. This is a much quicker cooling method than room cooling alone; however, it is important to make sure that humidity levels remain high enough to prevent the leaves from drying out.

Vacuum Cooling – Spinach may also be cooled using vacuum cooling. This involves placing wet spinach in a vacuum chamber and gradually lowering the pressure. When the pressure drops sufficiently the liquid moisture will shift into vapor form, using up heat in the processes and thereby lowering the temperature of the spinach.

Effective Spinach Cooling Systems from SEMCO/SEMCOLD LLC

SEMCO/SEMCOLD LLC is an industry leader in the manufacturing and installation of cooling and freezing systems. Our cooling systems are ideal for use with produce such as spinach and can easily be customized to fit the capacity demands and other unique concerns of each of our clients. We want to ensure that our clients get the most value from their spinach crop and that end consumers get the freshest, highest quality product possible.