Food Preservation


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Food Preservation

  1. 1. Understanding Food Chapter 7: Food Preservation
  2. 2. Food Spoilage <ul><li>Biological Changes </li></ul><ul><li>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. </li></ul><ul><li>Fermentation: The conversion of carbohydrates to carbon dioxide and alcohol by yeast or bacteria. </li></ul>
  3. 3. Food Spoilage <ul><li>Chemical Changes </li></ul><ul><li>Chemical reactions or changes also contribute to food deterioration. </li></ul><ul><li>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: </li></ul><ul><ul><li>Proteases, also called proteolytic enzymes, split proteins into smaller compounds. </li></ul></ul>
  4. 4. Food Spoilage <ul><li>Physical Changes </li></ul><ul><li>The most common physical changes occurring in foods as they spoil are evaporation, drip loss, and separation. </li></ul><ul><li>Dehydrate: To remove at least 95% of the water from foods by the use of high temperatures. </li></ul><ul><li>Freeze-dry: To remove water from food when it is in a frozen state, usually under a vacuum. </li></ul>
  5. 5. Food Preservation Methods <ul><li>Drying is the food preservation process that consists of removing the food’s water, which effectively inhibits the growth of microorganisms. Like: </li></ul><ul><ul><li>Sun Drying </li></ul></ul>
  6. 6. Food Preservation Methods <ul><li>Commercial Drying </li></ul><ul><li>The most important types of commercial drying are: </li></ul><ul><ul><li>Conventional: heat. </li></ul></ul><ul><ul><li>Vacuum: pulls the water out. </li></ul></ul><ul><ul><li>Osmotic: water drawn out by osmosis. </li></ul></ul><ul><ul><li>Freeze-drying: ice crystals vaporize. </li></ul></ul>
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  8. 8. Food Preservation Methods <ul><li>Sublimation: The process in which a solid changes directly to a vapor without passing through the liquid phase. </li></ul>
  9. 9. Food Preservation Methods <ul><li>Cure: To preserve food through the use of salt and drying. Sugar, spices, or nitrates may also be added. </li></ul><ul><li>Fermentation </li></ul><ul><li>Pickling uses vinegar to preserve foods. </li></ul><ul><li>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. </li></ul>
  10. 10. Food Preservation Methods <ul><li>Carbohydrates are required for the fermentation process. </li></ul><ul><li>Throughout Asia, vegetables are still commonly fermented. </li></ul><ul><li>In North America, foods most often preserved by fermentation are cucumbers, olives, and cabbage. </li></ul>
  11. 11. Food Preservation Methods <ul><li>The purpose of edible coatings is fourfold: </li></ul><ul><li>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. </li></ul><ul><li>2. To impart improved handling characteristics, such as the ability to bend more easily without breaking. </li></ul><ul><li>3. To improve appearance through increased gloss and color. </li></ul><ul><li>4. To serve as a vehicle for added ingredients such as flavors, antioxidants, antimicrobials, etc. </li></ul>
  12. 12. Food Preservation Methods <ul><li>Canning is a two-step process: </li></ul><ul><ul><li>First the food is prepared by being packed into containers, which are then sealed. </li></ul></ul><ul><ul><li>Then the containers are “canned,” or heated to ensure that all microorganisms are destroyed. </li></ul></ul><ul><li>Sterilization: The elimination of all microorganisms through extended boiling/heating to temperatures much higher than boiling or through the use of certain chemicals. </li></ul>
  13. 13. Pressure cooker Canner
  14. 16. Cold Preservation <ul><li>Refrigeration slows down the biological, chemical, and physical reactions that shorten the shelf life of food. </li></ul><ul><li>For safety purposes, refrigerators should be kept between just above freezing to no more than 40°F (4°C). </li></ul><ul><li>All perishable foods should be refrigerated as soon as possible, preferably during transport, to prevent bacteria from multiplying. </li></ul>
  15. 17. Cold Preservation <ul><li>Freezing makes water unavailable to microorganisms. </li></ul><ul><li>The chemical and physical reactions leading to deterioration are slowed by freezing. </li></ul><ul><li>Rancid: The breakdown of the polyunsaturated fatty acids in fats that results in disagreeable odors and flavors. </li></ul><ul><li>Freezer burn: White or grayish patches on frozen food caused by water evaporating into the package’s air spaces. </li></ul>
  16. 18. Heat Preservation <ul><li>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. </li></ul>