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Food Preservation
 

Food Preservation

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    Food Preservation Food Preservation Presentation Transcript

    • Understanding Food Chapter 7: Food Preservation
    • Food Spoilage
      • Biological Changes
      • Yeast: A fungus (a plant that lacks chlorophyll) that is able to ferment sugars and that is used for producing food products such as bread and alcohol.
      • Fermentation: The conversion of carbohydrates to carbon dioxide and alcohol by yeast or bacteria.
    • Food Spoilage
      • Chemical Changes
      • Chemical reactions or changes also contribute to food deterioration.
      • Enzymes play a significant role in catalyzing these reactions and can be categorized by the substance on which they act (substrate) or their mode of action. An example:
        • Proteases, also called proteolytic enzymes, split proteins into smaller compounds.
    • Food Spoilage
      • Physical Changes
      • The most common physical changes occurring in foods as they spoil are evaporation, drip loss, and separation.
      • Dehydrate: To remove at least 95% of the water from foods by the use of high temperatures.
      • Freeze-dry: To remove water from food when it is in a frozen state, usually under a vacuum.
    • Food Preservation Methods
      • Drying is the food preservation process that consists of removing the food’s water, which effectively inhibits the growth of microorganisms. Like:
        • Sun Drying
    • Food Preservation Methods
      • Commercial Drying
      • The most important types of commercial drying are:
        • Conventional: heat.
        • Vacuum: pulls the water out.
        • Osmotic: water drawn out by osmosis.
        • Freeze-drying: ice crystals vaporize.
    • http://www.mountainhouse.com/
    • Food Preservation Methods
      • Sublimation: The process in which a solid changes directly to a vapor without passing through the liquid phase.
    • Food Preservation Methods
      • Cure: To preserve food through the use of salt and drying. Sugar, spices, or nitrates may also be added.
      • Fermentation
      • Pickling uses vinegar to preserve foods.
      • Edible coating: Thin layer of edible material such as natural wax, oil, petroleum-based wax, etc. that serves as a barrier to gas and moisture.
    • Food Preservation Methods
      • Carbohydrates are required for the fermentation process.
      • Throughout Asia, vegetables are still commonly fermented.
      • In North America, foods most often preserved by fermentation are cucumbers, olives, and cabbage.
    • Food Preservation Methods
      • The purpose of edible coatings is fourfold:
      • 1. To increase shelf life by acting as a barrier to moisture, oxygen, carbon dioxide, volatile aromas, and other compounds whose loss would lead to deterioration.
      • 2. To impart improved handling characteristics, such as the ability to bend more easily without breaking.
      • 3. To improve appearance through increased gloss and color.
      • 4. To serve as a vehicle for added ingredients such as flavors, antioxidants, antimicrobials, etc.
    • Food Preservation Methods
      • Canning is a two-step process:
        • First the food is prepared by being packed into containers, which are then sealed.
        • Then the containers are “canned,” or heated to ensure that all microorganisms are destroyed.
      • Sterilization: The elimination of all microorganisms through extended boiling/heating to temperatures much higher than boiling or through the use of certain chemicals.
    • Pressure cooker Canner
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    • Cold Preservation
      • Refrigeration slows down the biological, chemical, and physical reactions that shorten the shelf life of food.
      • For safety purposes, refrigerators should be kept between just above freezing to no more than 40°F (4°C).
      • All perishable foods should be refrigerated as soon as possible, preferably during transport, to prevent bacteria from multiplying.
    • Cold Preservation
      • Freezing makes water unavailable to microorganisms.
      • The chemical and physical reactions leading to deterioration are slowed by freezing.
      • Rancid: The breakdown of the polyunsaturated fatty acids in fats that results in disagreeable odors and flavors.
      • Freezer burn: White or grayish patches on frozen food caused by water evaporating into the package’s air spaces.
    • Heat Preservation
      • Pasteurization: A food preservation process that heats liquids to 160°F (71°C) for 15 seconds, or 143°F (62°C) for 30 minutes, in order to kill bacteria, yeasts, and molds.