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Food Preservation by Freezing and Canning

Food Preservation by Freezing and Canning. Chapter 30. Freezing. Clarence Birdseye began frozen food industry in 1920s Research and Developments “Antifreeze” proteins - control size of ice crystals Air impingement – fast cooling Pressure shift – small crystals

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Food Preservation by Freezing and Canning

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  1. Food Preservation by Freezing and Canning Chapter 30

  2. Freezing • Clarence Birdseye began frozen food industry in 1920s • Research and Developments • “Antifreeze” proteins - control size of ice crystals • Air impingement – fast cooling • Pressure shift – small crystals • Time-temperature indicators – monitor temperatures

  3. Freezing Process • Three stages • Product lowered to freezing • Ice crystals form • Temperature lowered to storage temperature • Microorganism activity is minimal • Will grow after thawing • Enzyme processes may continue • Blanching

  4. Changes in Frozen Foods • Formation of crystals • Fruits and vegetables cells may be damaged • Rapid freezing favors small ice crystals • Enzyme Action • Blanching • Sugar or sugar syrups

  5. Changes in Frozen Food • Nonenzymatic Oxidation • Usually associated with fat • Fat of pork particularly susceptible • Desiccation • Moisture loss by sublimation • Freezer burn • Activity of Microorganisms • Inactive or minimally active at low temperatures • Growth and activity resume after thawing

  6. Freezing Techniques • Fruits • Vegetables • Meat, Fish, Poultry • Eggs • Prepared Foods

  7. Other Issues • Container selection • Use and management of freezer

  8. Canning • Application of heat to destroy essentially all microorganisms • Vegetative Cells and spores • Sealing product in sterilized containers

  9. Canning History • French prize • Nicolas Appert – 1809 preserved foods • Development of tin canister • Early 1800’s canned foods for British Navy • Commercial canning • Batch and continuous retorts • Aseptic canning • Retort pouch

  10. Home Canning • Containers – Glass jars • Pack methods • Raw • Hot

  11. Home Canning (Processing) • Boiling water bath (212°F / 100°C) • Must be high pH or ACIDIC foods • Tomatoes may or may not have adequate acid levels • Follow recommended time and temperatures • Pressure canning (240°F / 116°C) • LOW ACID foods must be processed with pressure • pH higher than 4.6 • Use pressure canner with accurate gauge • Adjustments necessary at high altitudes • Use recommended pressure and time • Allow pressure cooker to cool and depressurize

  12. Containers • Commercial canning • Tin-plated steel • Aluminum • Glass • Retort flexible packages • Home canning • Glass jars with self-sealing lids • No larger than quart size is recommended

  13. Additional Issues • Heat penetration • Obtaining a partial vacuum • Obtaining an effective seal • Handling after processing

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