Post on 25-Jul-2020
Preserving Your Garden’s Bounty
Jenny Rhodes and Lynn Little, Extension Educators
University of Maryland Extension
Two Methods of Canning Food
• Pressure Canning –low acid foods
• Water Bath Canning – high acid foods
How Canning Preserves Foods
• Prevents growth of bacteria, molds and yeasts
• Inactivates enzymes • Removes oxygen • Forms vacuum in jars
Temperatures for food preservation
Canning temperatures for low acid foods in pressure canner.
Temperatures used to destroy microorganisms in acid foods.
Temperatures prevent growth, but may allow survival of some microorganisms.
DANGER ZONE Temperature allows rapid growth of microorganisms.
Maximum Storage temperature for canned foods.
Best storage temperature for canned and dried foods.
Temperature where water freezes. Freezing temperatures slows growth of microorganisms, but some may survive.
Best storage temperatures for frozen foods.
Canning temperature for acid fruits, tomatoes etc.
low pH, high acid, fruits
high pH, low-acid, vegetables, meats, dairy, mixed foods pH 14.0
pH 1.0
What are Low-acid Foods?
• Foods that have a pH of 4.6 or higher
• All meats • Dairy products • Vegetables • Mixed dishes (vegetables mixed
with fruits or meats)
Recommended Canning Practices
• Selection and handling of foods
• Tested recipe • Equipment • Processing
What is a Tested Recipe?
• Comes from a credible source that uses USDA guidelines
Examples: Ball Blue Book, So Easy to Preserve • Has been lab-tested for time,
temperature and pH
• Do not alter ingredients • Changes pH of
food • Do not add extra
sugar or fat • Do not add
thickeners • Do not change the
size of food pieces
Follow Tested Recipes
Acidification Use commercially bottled
lemon juice and/or vinegar (5% acidity)
OR Citric acid
• Ascorbic acid ONLY prevents browning – Pure powdered form – Vitamin C tablets – Commercial mixes
Preventing Browning
Equipment
• Equipment – Jars, lids
– Canners
(1) (2) (3)
Canning Jars Use only mason-type jars • half pint (usually for jellies,
jams) • pint • quart • half gallon
(for high acid juices only)
Filling Jars Control Headspace
• Space between product and lid – ¼ inch for jams and jellies – ½ inch for fruits and tomatoes – 1 to 1 ¼ inch for foods processed in pressure
canners • Too little or too much space, jar may not
seal
Processing method
• Water bath canning –used for high acid foods –water reaches 212⁰, which
kills molds, yeast and some bacteria
• Large, cooking pot with rack • Flat bottom for electric range • Fill to 1 to 2 inches above tops of
jars
Water Bath Canner
Processing method
Pressure Canning • used for low-acid foods • water reaches 240⁰ F
at 10 psi and 250⁰ F at 15 psi, which kills molds, yeasts and bacteria, including clostridium botulinum spores
Types of Pressure Canners
• To be considered a pressure canner, the canner must be large enough to hold at least 4 quart-size jars.
Pressure Canners vs. Cookers
Pressure is the only way to increase temperature!!
Pressure canning kills microorganisms with • pressure • time • heat Increasing time in a water bath canner does not increase the temperature.
It Only Takes a Taste
• Powerful toxin • Attacks nervous system • Kills without immediate
treatment
Not recommended
• Open-kettle canning • Microwave canning • Dishwasher canning • Oven canning • Steam canning • Slow cookers, powders • Inversion method
Summary of Recommended Canning Practices
• Always use a tested recipe • Use water-bath canner for high acid
foods, pickles, jellies • Use pressure canner for low acid foods • Use mason-type jars and self-sealing lids • Process for specified time • Don’t rush the process!
Preservation Guidelines
• Selection of Food – Processing does not improve quality. – Choose highest quality available. – Preserve promptly. – Remember some foods don’t preserve
well. • Preparation
– Work under sanitary conditions. – Follow recommended procedures for the
method you have selected.
Hot Pack
Heat fresh food and liquid to boiling for 2-5 minutes before filling jars. This helps: • remove air • shrink food • keep food from floating • increase vacuum seal • improve shelf life, color and flavor • Increase yield per jar
Raw Pack Pack raw, unheated food into
hot jars; then cover with boiling liquid. Raw-packed foods should be packed tightly; shrinkage occurs during processing. Not recommended for low-acid foods.
Storing Home-canned Food
• Remove ring from sealed jar • Clean lid surface • Label and date jar • Store jars in a cool, dark, dry place • Avoid temperature extremes • Use within 1 year
Signs of Spoilage
• Bulging lid • Unnatural color • Rising air bubbles • Streaks of dried food • Spurting liquid • Unnatural odor • Mold growth under lid
DO NOT TASTE FOOD FROM UNSEALED JARS
Freezing Food
Advantages of Freezing
• Many foods can be frozen. • Good natural color, flavor and
nutritive value can be retained. • Texture usually better than for
other methods of food preservation.
• Foods can be frozen in less time than they can be dried or canned.
Disadvantages of Freezing Foods
• Texture of some foods is undesirable because of changes due to the freezing process.
• Storage space is limited by how much
the freezer will hold.
How Freezing Affects Food
• Enzymes in Vegetables – Are destroyed by heat, called blanching,
before packaging and freezing.
• Enzymes in Fruits – Usually controlled by ascorbic acid (also
called vitamin C) or some other additives. – Fruits are usually not blanched, but can be.
• People like them raw and uncooked.
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How Freezing Affects Food
– The water in food freezes and expands.
– Ice crystals cause the cell walls of fruits and vegetables to rupture, making them softer when thawed.
– Some vegetables with very high water content do not freeze well: celery, lettuce, some tomatoes.
Freezing Advice
• Freeze foods quickly. – Set freezer temperature at -10o F at
least 24 hours ahead of freezing large quantities of fresh food.
– Spread packages out around the freezer, until frozen, then stack.
• Hold at 0oF for best quality.
Preventing Fruit Darkening During Preparation (Peeling, slicing, etc.)
– 1 tsp (3000 mg) ascorbic acid to one gallon of cool water
– Commercial ascorbic acid mixture – Heating the fruit
– The following do not work as well:
• Citric acid solution • Lemon juice • Sugar syrup
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Preventing Discoloration During Freezing
• Ascorbic Acid Mixtures – “Fruit Fresh” and others. – These have some other added
ingredients. – Follow package directions to obtain
correct strength of ascorbic acid.
Preventing Flavor and Color Changes in Vegetables
Blanching
• destroy enzymes • soften hard veggies to
make packaging easier. • remove some
microorganisms. • Check required blanching
times for each food.
How to Blanch Vegetables
• Steam Blanching – Use kettle with tight lid
and basket. – 1” to 2” of boiling water in
bottom of pan. – Vegetable should be in a
single layer in basket. – Start timing when covered.
Drying Foods
Drying is New Again
• Alternative to canning & freezing • Simple, safe and easy to learn • Can dry year round • No refrigeration needed • Takes little space
How Drying Preserves
• Removes moisture from food so bacteria, yeasts & molds can’t grow and spoil food
• Slows down action of enzymes but doesn’t inactivate them
Temperatures for Drying
• Optimum temperature for drying food is 140°F
• If higher temps are used, food cooks instead of drying
• Avoid “case hardening” – dried outside and moisture is trapped inside – mold results
Ways To Dry Food
• Foods can be dried in the sun, but often doesn’t work well as you need several days of high temperature and low humidity
• Dry in an oven • Dry in food dehydrator
Drying Fruit
• Preparing the Fruit – wash fruit and core, if needed
• Fruits can be halved or sliced and some left whole
• Thin, uniform, peeled slices dry fastest • Apples can be cored and sliced -
wedges, rings • Bananas can be sliced • If fruit dried whole, “check” or crack the
skin to speed drying – cranberries – place in boiling then cold water to “check”
Pretreating the Fruit
• Sulfite Dip • Ascorbic Acid • Ascorbic Acid
Mixtures
• Fruit Juice Dip • Honey Dip • Syrup Blanching • Steam Blanching
Drying Vegetables
• Preparing the vegetables –Wash, trim, peel,
according to directions –Uniform pieces –Dry as soon as possible
after picking
Drying Herbs
• Harvest young, tender leaves • Rinse gently in cool water and
drain well on paper towels • Hang dry herbs with long stems
in a warm, dry, airy place – not in the sun
• Dry seeds and herbs with short stems on trays
Drying Sunflower Seeds
• Select sunflowers with dry stalks
• Remove seeds, washing and drying, if plants were sprayed
• Dry in a warm place for a week
• Alternate – hang flowers in cool, dry place for a month
Preserving Your Garden’s Bounty
Thank you!