Question of the Week
What can you tell me about planning the basic infrastructure for small to mid-size vegetable operations, specifically for harvest/packing shelters, walk-in coolers, and washing facilities?
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Answer: First, be mindful of the fact that the new Food Safety Modernization Act (FSMA) being written up by the FDA will have a lot of impact on your packing and storage facilities. The Act is not being enforced yet, but it soon will be. To learn more, visit http://www.fda.gov/Food/GuidanceRegulation/FSMA/ucm334114.htm. It is recommended that you really study this page and all the internal pages to which it directs you. These food safety regulations will limit some of the designs of packing sheds that used to be acceptable.
As far as sizing of each of the operations, e.g., the packing line, the wash tub, and the coolers, you need to think about how much product you will be harvesting and how long you intend to hold it on your property. Let's use the crop of summer squash as an example. Let's say your projected yield is about 1,000 boxes per acre, you will harvest that acre over a four-week period, and you will pick the crop twice per week. That means that you will harvest that acre of squash eight times, with an average harvest of 125 boxes. But remember you won't get harvests of 125 boxes each time. At the start (and finish), you will get less than 125 boxes per harvest. In the middle of the harvest, you will get much more than 125 boxes per pick. My experience with summer squash was that the third week of the harvest actually produced 40% of the total yield, so each of the harvests that week would deliver 200 boxes, for a total of 400 boxes that week. So your facilities have to be designed to process up to 200 boxes per shift even though the average harvest for that one acre is 125 boxes. As a rule of thumb, your packing line needs to be designed to run double the product flow from what you think your average will be.
Unless you also have the time and space and staff available to completely dry your produce after you wash it, I would not wash it in the first place. Back to the example of summer squash, unless the squash is really dirty when harvested it because it rained that day or the day before, it's a better approach to simply not get the squash wet. Boxing up squash that is not completely dry is a recipe for disaster. The product will have no shelf life. The same goes for tomatoes, cukes, peppers, melons, etc. Greens are an exception, as they are generally always washed.
Regarding sizing a walk-in cooler, the following webpage shows the correct storage temperatures for different fresh produce items: www.freshpoint.com/produce/handling_guide.html#. This is important as you don't want to store everything together in the same place at the same temperature just because items were harvested at the same time. In addition to questions about what products to store with each other (and what NOT to store with each other), you need to consider how long you think you will have to hold a given harvest. A cooler should probably be sized to hold one week's worth of production. If you hold a given harvest of something in your cooler for more than one week, chances are that it is not worth taking up that space in the cooler. Back to that acre of summer squash again, your weekly harvests over the four-week period will be 100 boxes, 300 boxes, 400 boxes, and then 200 boxes. Your sales will have to match up with that input flow as close as possible or you will be building up inventory in the cooler.
You could make the same calculations for one acre of whatever else you are harvesting, add all those boxes/week together to see how many boxes you probably will need to be storing. Each box you store will take up about 1.5 cubic feet of space. You don't want to store boxes on the ground in a refrigerated cooler, nor do you want to stack them all the way to the ceiling. You don't want to block air flow within the cooler. So if you had a cooler that was 8 feet tall, 20 feet long, and 15 feet wide and you stored boxes four inches off the floor and four inches from the top, you would have available approximately 2,200 cubic feet of storage. Dividing that by 1.5 and allowing for walking space, you could store about 1,300 to 1,400 boxes within that cooler, not considering issues of different temperatures needed for different crops.
For more information, see the ATTRA publication Postharvest Handling of Fruits and Vegetables, available at https://attra.ncat.org/attra-pub/summaries/summary.php?pub=378.
Also refer to resources available from the Postharvest Technology Center, University of California http://postharvest.ucdavis.edu/.