Help! My Greens Are Brown!

We have had a lot of questions over the last couple weeks about why the greens have been turning brown more quickly in the summer than in the winter. The short answer is heat.

Greens are out in a field under the hot sun until they’re picked. Once picked, a large commercial farm will immediately run the greens through either a hydro cooler, vacuum cooler, or a pressure cooler. Hydro coolers run produce through an icy cold bath and are commonly used for avocados and other stone fruits. This method isn’t great since it can leave you with water soaked and transparent leaves that have to be trimmed off. Vacuum coolers are perfect for greens, but can take more than five years for a high volume farm to pay off.

A pressure cooler is created by using a fork lift to place stacks of produce pallets in two rows on either of a large cooler fan. The pallets create a tunnel and are covered by a tarp to force the air from the fan through the tunnel. The pressurized cold air leaches any remaining sun heat out of the plants and temporarily stops the breakdown of the plants’ cells.

Small local farms don’t usually have access to these types of advanced and expensive cooling systems. They are a serious investment for such a low profit market and require a lot of open space to use that most small farms can’t really spare. Small farms usually use walk-in style coolers, which take a bit longer to remove the same amount of heat as the other types of coolers.

The time of day they are harvested impacts the amount of heat that is carried into the cooler. A one acre field of romaine lettuce harvested in the morning contains about the same amount of heat as 1/4th of an acre field harvested in the early afternoon. Another factor is how fast the greens are placed in the cooler after being picked. The longer the greens have to wait before going into the cooler, the less shelf life they will have.

Knowing the shelf life of your greens can help you plan which greens to use first when planning meals throughout the week. According to the Canadian Produce Marketing Association (CPMA), lettuce variety greens, like romaine, green & red leaf, or spinach, only last about one week in refrigerated storage. It is recommended to wash them before storing. Other varieties of greens, like collards, kale, and chard, only last between 2 – 4 days refrigerated before they start to develop spotting and it is recommended that you do not wash them before storing. So use the chard or kale right away and save the lettuce for later in the week.

There is also a great technique from Discovery Organics for extending the life of your greens that you can do right away. Immediately remove any brown or over-saturated leaves and trim the stem, so that it is freshly cut. Then, immerse the lettuce in bath temperature water for about one minute. Immediately immerse the lettuce into icy water following the warm water and leave for 2-3 minutes. Plants are made up of cells, just like we are, so this technique works similar to washing your face. The warm water opens all the pores on the leaves and allows them to suck in water. The cold water is quickly absorbed and causes the pores to seal in all that fresh cold water. Just make sure to dry any excess water off of your kales and chards before sticking them into the fridge.

Our newsletter is written for you, so feel free to let us know what interests you! I’m always happy to write articles regarding questions you might have or topics you’re interested in. ~ Rachel