customers expect a lot from you; sustainable methods of production,
responsible stewardship of your farm, high quality and a fair price.
Chances are they also want the produce they buy to last a long time at
their home in the fridge. How you take care of your vegetables after
they are harvested might make you a hero in the eyes of your patrons,
but they will definitely remember if it spoils quickly.
It is all about the heat.
The quicker you can get it out of the hot sun, the better.
rates are a function of temperature, and are best slowed by rapid
cooling. The microorganisms that cause decay are also slowed by lower
Most walk-in coolers do not have the capacity to pull field heat out of produce.
vegetables that are not properly cooled in the walk-in not only wastes
energy it prolongs the time that the produce will be prone to an
increased rate of decay.
The most common way to initially cool produce involves cold water.
Since all of the water is coming in contact with food, it should be potable.
In VT we are required to test our water as part of our Organic Certification.
A system as simple as a tank of cold water is a good start.
Two tanks are better.
As the vegetables are washed, the water gets dirtier and warmer.
Both are a problem, any pathogens present will be transferred to all the produce that comes in contact with the water.
Having two tanks allows one tank to be freshly filled as the other one gets dirty and warmer.
the heat that is coming out of the food has to go somewhere, and the
tanks ability to adequately cool will be diminished over time.
Therefore it is always a good idea to change the water frequently.
A more elaborate system is a hydro cooler.
an enclosed space has a stream of refrigerated water running over the
produce. If fresh water is used, it allows the temperature to remain
constant, and also reduces the risk from cross contamination.
A true hydro cooler is an expensive item, and is out of the reach for a lot of growers.
Top icing is another way to get a good reduction in temps for a cheaper cost.
It is not appropriate for all crops however, and the use of ice on some can cause more harm with chilling injury.
USDA has a publication, Agriculture Handbook Number 66, which lists the
ideal temperatures for the storage of every crop. Itís a great
resource, and has lots of information in it, including approximate
length of storage. I got my copy from our extension agent, and although
it may sound dry, it is very interesting and useful.
A good example at our farm is when we harvest leafy greens.
We harvest as early as we can in the day, before the fields have had a chance to warm up from the sun.
We put the greens in the shade and run them back to the barn as soon as we can.
Once we are at the barn, everything is off loaded onto a cement slab and hosed off with cold water.
There is only so much time before the sun gets high, however.
At some point the sun comes out full force, and the plants start to get warmer.
At this point we shuttle back to the barn more frequently.
Once the produce has been washed, we let it drain for a few minutes, and then it goes into the cooler.
We have learned to stack the boxes loosely so air can get around them better to aid in the cooling.
We try to have most of what will leave the farm in the cooler for one full day.
That way I know that when it gets to my customers it is thoroughly cooled and stable, and will last a while for them.
On a side note, we have been putting head lettuce in a sleeve for four years now, and the difference is amazing.
agree that the world needs less plastic, but I would argue that there
are few gains made when the product has to be thrown out because of its
sleeves protect the head from broken leaves and make the lettuce much
easier to handle at market. They also keep it hydrated much longer.
This all translates to a better product with increased shelf life.
I still remember early in our career when the cost of a walk-in cooler seemed prohibitive.
Now I canít imagine farming without one.
If you are a young grower, it should be high on your list of must haves.
Sometimes the difference between a sale and the compost pile is only a few days, and a cooler can quickly pay for itself.
Wishing the best to you and yours.