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ENST 310: Agroecology Food Preservation Lab: Water Bath Canning Background You’ve spent countless hours in the heat of the summer tending your vegetable garden. You’ve used the best organic practices and followed all the best sustainable soil methods. And now, you’ve got more tomatoes, bell peppers, onions, and cucumbers than you can possibly eat before they go bad! What are you going to do with all this food? How can you preserve it so that it will last through the winter, when your garden is sleeping and the grocery stores are importing vegetables from Mexico? Vegetables and fruits begin losing some of their vitamins when immediately when harvested; in fact, nearly half the vitamins may be lost within only a few days! Refrigeration and cooling delays that loss slightly – cooled produce loses half or more of some of its vitamins within a week. Freezing is another option, but space is usually limited and the high water content in most vegetables changes their texture upon thawing. Canning can be a safe and economical way to preserve quality food at home. Though the heating during canning will cause some vitamins to deteriorate, most are preserved for up to a year or more. Canning food removes oxygen, destroys enzymes (i.e. stops the ripening process), and prevents the growth of undesirable bacteria, yeasts, and molds. Food acidity and processing methods There are two main ways of canning foods – water bath canning and pressure canning. The biggest food safety concern in choosing a method is killing and stopping the growth of Botulinum bacteria (which causes botulism), and there are two main factors that affect it’s growth: heat and acidity. Botulinum spores are generally hard to destroy at boiling-‐water temperatures, so foods that are neutral (not acidic) require a higher canning temperature. Sometimes these temperatures are higher than that we can achieve under atmospheric pressure, and are therefore only safe to can in a pressure canner, where the food can reach the temperature needed to kill the spores. We can also alter the pH of the food; high-‐acid conditions (pH < 4.6) prevent the growth of Botulinum bacteria. Acid can either be a naturally occurring acid (e.g. that found in most fruits), or we can add a liquid acid (e.g.
vinegar or citrus juice in pickled food). Most mixtures of low-‐acid and acid foods have pH values above 4.6, so we often add lemon juice, citric acid, or vinegar to make them more acidic and therefore safe for water bath canning. Tomatoes usually are considered an acid food, but many varieties are known to have pH values slightly above 4.6, so we will be adding lime juice to ensure a proper acidity and safety of the end product. Bell peppers, onions, and garlic are all low acid foods as well. Other factors that affect water bath canning procedures include altitude (because of the change in atmospheric pressure) and processing time. Lab objectives:
• Become familiar with water bath canning techniques and methods of preserving foods
• Understand the difference between water bath canning, pressure canning, and other methods of shelf-‐stable food preservation
Materials We will be working in four groups. Each group will make approximately 6-‐8 pints of salsa. Each group needs the following: Food prep (pre-‐canning)
• Knives • Cutting board • Colander
• Saucepan • Scale • Wooden stirrer
• Measuring cups and spoons
• Latex gloves Water Bath Canning Tools
§ Canner: Must be at least 2 inches taller than the largest jar you use with a rack for holding the jars off the bottom of the canner. Jars must be covered by 1 inch of water; the additional space is to allow room for a vigorous boil during processing.
• Jar lifter: To lift jars out of the boiling water. • Magnet: for lifting lids out of boiling water • Funnel: For filling jars 1-‐ pint canning jars (e.g. Mason jars) with 2-‐piece metal lids • Rags • Chopsticks: For removing air pockets
Food: See recipe below for exact quantities
• Tomatoes • Onions • Bell peppers
• Garlic • Jalapenos • Salt
• Lime juice • Cumin • Cilantro
Pocedure Short version:
1. Sterilize jars 2. Make food 3. Fill jars 4. Process
Long version: 1. Examine jars for any nicks,
cracks, uneven rim surfaces or other damage – do not use damaged jars.
2. Place jars into canner on canner rack (include 1 or 2 extra jars, if possible, to accommodate varying yields). Fill with water to at least 1 inch over the top of the jars. If you use unfiltered, hard water, add 2-‐3 tbsp vinegar to the water to prevent mineral deposits from collecting on your jars. Boil jars for 15 minutes to sterilize.
3. Place the jar lids into a small bowl and cover with boiling water; let sit until ready to process. Set screw bands aside.
4. Prepare recipe. (See below) 5. While recipe is cooking, set up your canning area. Clear a spot on the countertop,
lay out a towel, funnel, magnet, lids in water bowl, clean towel, jar lifter, screwtop bands, and potholders.
6. Fill jars: • Remove jars from the canner, pouring hot water back into the canner (keep the
heat beneath the canner on low, and keep the canner water at a low simmer while filling jars) and place on the towel.
• Set funnel in the top of the jar and ladle the prepared food into the jar, leaving ½ inch headspace, which is the space between the top of the jar and the top of the food (See figure above).
• Tap the bottom of the jar on your work surface a few times. Slide chopstick down between the food and the edges of the jar, moving the handle up and down as you rotate the jar. This releases any air pockets that may cause seal failure; adjust headspace if necessary by adding more salsa.
7. Dip the edge of a paper towel or clean kitchen towel into the water and wipe the jar rim and threads. Remove ALL food on the jar rim.
8. Using magnetic jar lifter, lift a lid out of the bowl and gently place on the jar; try not to handle it with your hands.
9. Place the screwband on the jars and tighten until it is just fingertip tight (if it is too tight, pressure built up inside the jar from the boiling food will not be able to release).
10. Using jar lifter, return the jars to the canner pot. Do not process jars that are not completely full. You can store this food in the fridge and use within a few weeks.
11. Replace the canner lid and turn the heat up to high to bring the water back to a full boil. Once boiling, start your kitchen timer and process at a rolling boil for the time specified in the recipe.
12. When the timer goes off, turn off the heat, remove the canner lid, and let the jars rest in the canner water for 5 more minutes. Then, remove the jars from the hot water, and place them on a kitchen towel. Be careful not to tilt the jars excessively or let food to touch the jar lid, as it may interfere with the jar producing a tight seal. You should start hearing the “ping” that signals a jar lid sealing within minutes, but for different recipes, it takes different amounts of time.
13. Allow the jars to rest undisturbed for 24 hours. If any jars did not seal, either put that jar into the fridge and use within a week or two, or re-‐process (in a clear jar, with new lids, etc).
Recipe for salsa
• 1200 g tomatoes, chopped, skinned, and drained • 1.5 cup lime or lemon juice* • 660 g onions, diced • 390 g bell peppers, diced • 90 g jalapeno, diced (leave seeds for hot salsa, remove for medium salsa, OMIT for
mild salsa*) • 60 g garlic, diced • 1.5 tsp salt • OPTIONAL: cilantro and/or cumin, to taste *Notes:
1. Lemon juice will give a more mild taste to the salsa, lime will give it a more “authentic” flavor
2. If omitting jalapenos, add extra 90 g bell peppers Prep vegetables: The tomatoes we’re using have been frozen and thawed, so we need to skin them and drain their liquid (to prevent a watery salsa). Loose skins should peel off easily. Dice tomato flesh into approximately ¼ inch cubes and drain the juices through a colander. Dice onions and peppers into approximately ¼ cubes. De-‐seed jalapeño peppers (see note above). Mince garlic or use garlic press. Weigh the vegetables AFTER prepping. Combine all of the ingredients in a saucepan and bring to boil over medium heat while stirring. Reduce heat and simmer for 5-‐10 minutes, or until thickened slightly. Fill jars according to process outlined above, and process for 15 minutes in a boiling water canner. Sources: http://www.motherearthnews.com/real-‐food/canning/water-‐bath-‐pressure-‐canning-‐zecz11zsmi.aspx USDA Complete Guide to Home Canning, available online: http://nchfp.uga.edu/publications/usda/GUIDE%201%20Home%20Can.pdf