Food Preservation: Storage and Processing

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Food PreservationStorage and Processing

• By
• Robert Tomesh
• UW Extension

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Food Preservation(Demand for food is continuous)
Processing (kill tissue)
Storage (Tissue lives)
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Storage (tissue is living)

• Slow down respiration by cooling
• Remove field heat
• Reduce microbial growth
• Refrigerated and atmospheric control systems
• Root cellars, caves
• Bury in soil

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Processing (kill tissue)

• Drying
• Canning
• Freezing
• Preservation
• Fermentation microbial decompostion resulting in
  alcohols, vinegar, lactic acid (kraut)(pickles)
• Chemicals salt, sugar, vinegar

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Guidelines for Fresh Storage

• Store produce that is free from
• Cuts
• Cracks
• Bruises
• Insect damage
• Signs of disease
• Mechanical damage

Damaged produce could spoil the entire catch of
stored produce.
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Options for Damaged Produce

• Use any damaged
• produce for immediate
• cooking or consumption
• or for food
• preservation.

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Produce Harvest Care

• Treat produce as if it were fine china.
• Tossing or dropping produce may not leave visible
  bruises, but decay may begin under the skin.
• Not all produce should be washed.
• Avoid water borne bacteria and fungi.
• Avoid abrasions which may lead to water loss.

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Curing Produce Improves Shelf-life

• Curing heals or suberizes injuries
• Root crops
• Dries outer leaves
• Onions, leek, garlic
• Allows for cutin and waxes to be secreted to
  outer epidermis
• Cucurbits

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Reduce Field Heat in Produce

• Harvest in early morning
• Harvest on a cool day
• Harvest root crops when soil temperature begin to
  drop but before freezing

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Storage Facility Conditions

• Keep storage facility clean
• Remove all containers and produce once a
  yearspring cleaning
• Remove all deteriorating produce
• Maintain proper temperature
• 34 to 40 degrees F. for root crops
• 50 degrees for bulbs, squashes
• Maintain proper humidity
• Prevents shrinkage (wrinkling)

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With Proper Storage Conditions

• Potato---------------------5 to 8 months
• Onion----------------------5 to 8 months
• Winter Squash----------3 to 6 months
• Carrot---------------------4 to 6 months
• Dry beans--------------------12 months
• Green tomato-------------2 to 6 weeks
• Pepper----------------------------10 days
• Cucumber------------------------14 days

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Home Basement

• Often too warm for storage
• Ideal for ripening tomatoes
• Short term storage for potatoes, sweet potatoes,
  and onions (3-6 weeks)
• Choose an area near a north wall

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Pit and Mound Storage

• Not protective enough for Wisconsin winters
• A 10 inch layer of straw or leaves at base and
  over pile
• Pile then covered with soil and protective
  material to shed water
• Once opened, produce must be used

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Hole Dug into Soil

• Dig deep enough that top of produce is a foot
  below soil linesoil freezes but is modified to
  about 30 degrees
• Mound soil over storage area to allow for water
  run-off
• Mulch area over mound
• Barrel, waste basket can be buried

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Buried Insulated Box

• Locate in protected areabasement window,
  breezeway, inside non-heated building

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Other Storage Methods

• Garden Storage
• Second refrigerator
• Involves electrical costs
• Traditional storage cellar
• Initial investment and structure design
• Insulated storage room in house
• Designed on north wall, uses venting to manage
  temperature or refrigerated

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Garden Storage

• Root crops such as beets, carrots, rutabagas,
  parsnip and turnips can be left in the garden
• Wait until ground is cold before mulching
• Apply a heavy layer of mulch (bales) to prevent
  the soil from freezing
• Produce flavors become sweeter and milder

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Processing Systems

• Drying
• Canning
• Freezing
• Preservation
• Fermentation

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Food Drying

• Most ancient method of food processing
• Dehydration stops produce respiration, enzyme
  activity and microbial acitivity
• Sun drying, heat drying, freeze drying
• 5-10 of fresh weight

Food Dehydration
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Canning

• Involves heat sterilizationkills enzymes and
  microbes
• Most cost effective method for long term
  processing
• Problemloss of quality
• Store in dark
• Clostridium botulinum

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Freezing

• Spoilage and enzyme activity stops at 32 degrees
  F.
• Freezing process should be quick to maintain
  produce integrity
• Water crystals can puncture cell walls
• Most expensive method of preservation

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Preservatives

• Chemicals like salt, sugar, vinegar that
  inactivate enzymes and microbes
• Fermentation a natural preservation process of
  microbial decomposition
• Alcohols
• Vinegars
• Lactic acidcabbage to kraut

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Summary

• The demand for food is continuous
• May have 2 month growing period as in northern
  Wisconsin
• Preservation includes
• Storage systems-produce is living
• Processing systems-produce cells are killed