The Call and Times, Column 2 – Food Preservation

18 02 2014

(November 1, 2013)

The Urban Farmer

Put ‘Em Up – Preserving the Fall Harvest

            As I settle down after a long day of preserving, or “putting up” the last big harvest of the season, I am inspired to write this column. For urban farmers, especially here in New England, one important consideration is how we plan to save the warm season’s bounty for the cold winter months. Whether to ensure a food supply in the non-productive season, or to preserve the flavors of summer, we must keep this task on our minds before the weather turns and the tomatoes bear their last ripe fruit. In today’s column, I’d like to discuss with you some of the important methods of preserving the fall harvest for winter – freezing, drying, root cellaring, and canning.

One of the most popular, and arguably the easiest, techniques for preserving your fruits and vegetables is to freeze them. If you plan to use freezing as your primary storage, or are projecting a big harvest or farmer’s market purchase, a standalone chest freezer may be a worthwhile investment. But even with a split refrigerator-freezer like the one in my kitchen, freezing can be an important part of your preservation effort. Certain produce, such as peppers, tomatoes, and berries, can be frozen with minimal processing. Others, like peas and beans, carrots, and broccoli, must be blanched before they are frozen to destroy enzymes that ruin the quality of the food. In blanching, you heat the vegetables in boiling water or steam for a predetermined amount of time, and then immediately immerse them in ice water to stop the cooking process, before freezing them. The internet is a good source of further information on blanching. As a final point: freezing produce, while easy and safe, tends to consume a lot of space in your freezer, space which might be better used for energy-dense foods like meat. When possible, it is worth considering other methods of food preservation.

Another popular and versatile food preservation technique is drying. The basic principal is that by removing most or all of the water from the food, you create an environment in which bacteria and mold are unable to grow – rendering it shelf-stable for at least a few months. Foods with relatively low water content, like herbs or cayenne peppers, can be dried indoors, strung from the ceiling or spread out on a drying rack. For thin slices of any food, an outdoor solar dehydrator is a quicker, low-energy option. But to dehydrate foods with higher water content quickly enough to prevent spoilage, an electric food dehydrator, or an oven set to a low (~200°F) temperature may be necessary. Some dehydrated foods, like herbs, can be used in their dried state, while others, like sundried tomatoes, can be partially reconstituted in cooking to revive the tastes of summer.

For certain crops, the best storage technique is root cellaring, which basically takes advantage of the crop’s characteristic shelf-stability. This method traditionally required the construction of a small underground enclosure, called a root cellar, which gives it a somewhat higher initial cost than freezing or dehydrating. It is possible, though, to successfully root cellar in any space that is cool (not freezing), dry, and dark, such as a basement or even a kitchen cabinet. Crops that do well when root cellared are those with thick or tough skin, like winter squash and apples, those with low water content like grains, and the method’s namesake, root crops (carrots, potatoes, and onions). Depending on the food, this technique will preserve quality for a few months to over a year. It is important to select fruits or vegetables whose skins are not damaged and which are fresh and of generally good quality, and to store them in such a way that individual pieces are not touching one another.

Finally, what most see as the epitome of home food preservation, is the art of canning, the long-term storage of foods in sealed and sterilized glass jars. Much of the backyard bounty that we urban farmers hope to enjoy during the winter is either too high in water content, making it bulky to freeze and difficult to dry, or not inherently shelf-stable, making root cellaring impossible. Foods like berries and other fruits, tomatoes, and even many vegetables can be canned in one of two ways, boiling water bath or pressure canning. The science and art of canning is far too broad for me to even begin to describe here, so I will direct you to the “Ball Blue Book” or a similar guide to canning for detailed instructions. Canning was probably involved in your grandparents’ famous jam or brined pickles, so I would be hard-pressed not to point you to their old recipes as well. But as a word of warning: canning creates high sugar, high acid, and low oxygen conditions in order to prevent most spoilage. However, if sterilization by heating is not done properly, these conditions are ideal for the growth of botulism, a toxic soil-borne bacterium. So if you want to try your hand at canning, I have to stress that you follow the recipe and cooking instructions to the letter, and for good measure, say a little prayer before you tuck in six months down the road. Lest I’ve scared you off from this rewarding food preservation technique, you should know that in 2011, the CDC reported only 2 cases of foodborne botulism as the result of home canning in the U.S., neither of which resulted in fatality.

[Note: After the publication of my last column, a friend pointed out to me that I failed to mention the issue of contaminated soil. In urban areas, it is sometimes the case that past industrial activity has left lead or other contaminants in the soil. So it’s probably best, if your land could hold this type of contamination, to either send a soil sample to University of Massachusetts Amherst for testing, or use raised beds to guarantee the quality of your soil. A special thanks to Dave Fisher for bringing this to my attention.]

My column appears on the first Friday of each month in The Woonsocket Call and The Pawtucket Times. The above article is the property of The Woonsocket Call and The Pawtucket Times, and is reprinted here with permission from these publications. These are excellent newspapers, covering important local news topics with voices out of our own communities, and skillfully addressing statewide and national news. Click these links to subscribe to The Woonsocket Call or to The Pawtucket Times. To subscribe to the online editions, click here for The Call and here for The Times. They can also be found on Twitter, @WoonsocketCall and @Pawtuckettimes.

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