Canning Basics (Or, How to Deal with Your Fruit CSA and Not Get Botulism)

Having been in Europe for spring and most of summer, I missed the opportunity to sign up for a CSA share.  I was devastated until I saw an announcement for a fruit-only CSA, only just starting in August and being distributed quite close to my new Brooklyn apartment.  In a euphoric fit, I signed up for a half-share.  I saw lots of stone fruits in my future (so does Cathy from Not Eating Out in New York!), as well as a few peach capreses.  But what to do with all that other fruit?  Enter canning!

I signed up to take a class at the Brooklyn Kitchen with a professional canner.  As scary as it seems at first glance (fatal food poisoning! Lots of boiling water!), it turns out that if you follow a few simple rules of thumb, your chances of accidentally growing botulism or causing yourself any other harm are actually quite low.  The rules are:  keep the acidity of your food high (or the pH low), keep the temperature of the food high, keep all of your surfaces clean, and keep the food in whatever form of processing you use for a sufficient amount of time (if applicable).

What do you need to can?

This is the equipment our instructor recommended:

- If you are using the water bath method: a large pot; a jar rack or lots of clean towels for the bottom of the water bath; jar tongs.

- A large pot for boiling water and sterilizing jars

- A smaller pot for sterilizing screw rings and lids (these do not need to be boiling) and a magnetic wand for lifting the lids out of the water.

- Canning jars, lids, and screw rings.

- A ladle and funnel for scooping the food into the cans.

- Clean cloth and paper towels.

What should you know about acidity and canning (and botulism)?

Not to wig everyone out, but the bacteria spores that cause botulism are actually found on most fresh food.  However, because they only grow where there is no air, botulism is a singular risk of canning, since in the process of canning you are removing all air from the area around your food.

Most food has a low level of acidity.  This is true for everything from poultry to peanuts, and it applies to almost all fresh vegetables (including the ones you would can).  Most fruits are more acidic, but may not be acidic in and of themselves to ensure safe canning.  In order to keep botulism and other bacteria out, you must ensure that the acidity of your food drops below 4.6 pH.  To do this, most canning recipes include lemon or lime juice, citric acid, or a vinegar (for savory foods like pickles and tomatoes).

Similarly, it is important to make sure that your food reaches a high enough temperature for a long enough time before placing it in a can.  It is recommended that food reach a temperature of at least 180 degrees Farenheit, either before being placed in cans using the hot-fill method or during processing in the hot water bath (see below).

There are three methods for processing your canned goods (processing seems to be a jargon-y term meaning to seal the can and ensure proper preservation):

- The boiling-water bath – after you have prepared your food and placed it in the jars, you place the jars in a boiling water bath, covered with at least three inches of water, for a prescribed amount of time to ensure a seal.  The USDA Canning Guide indicates processing times for many common canning foods.

- The hot-fill – this is best for small batches of more acidic food and smaller-sized cans.  By placing sufficiently hot food in a small can and immediately closing the can, you will create a vacuum that will in turn create a seal.

- The pressure canner.  I did not learn anything about this method, but apparently you cannot use it for making jams.

And now, for the main event: how to make something to be canned!

Blueberry Lemon Honey Jam

Ingredients

10 pints of washed blueberries

1 cup of honey

Zest of 3 lemons

Juice of 5 lemons (you can also use lemon verbena)

How to prepare:

Place all ingredients in a large pot over medium-high heat and bring to a boil.  After it boils, lower heat and simmer for about an hour.  Stir often to avoid scorching the bottom of the mix, particularly as the jam thickens.  Taste occasionally, add extra sweetener to taste.  We did not add any when we made this recipe.

Test to see if the jam is ready by placing a small drop on a plate that has been in a freezer.  When everything reaches room temperature, if the jam is ready it will remain congealed.  If it is not quite cooked down enough, a runny ring of water will form around the edge.

When the jam is ready, clean the lip of the jar an additional time using hot water and a paper towel.  Use the ladle and funnel to scoop the jam into the cans, leaving 1/4” headspace at the top.

Again, clean the inside and outside of the lip with a paper towel and hot water.

Using the magnetic wand, place the lids on the jars.  Remove the screw rings and screw tightly to jar.

We were using small jars, so we used the hot-fill method.  Allow the sealed jars to cool at room temperature until the lids pop, indicating they have sealed.

Because this jam is low in sugar, it will only last about 2-3 weeks once opened, and will store for about 2 years before opening.