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  1. 1. F O OD P RE S E R VA T I O N
  2. 3. <ul><li>BY SHUMAILA TABASSUM </li></ul><ul><li>DEPTT OF BIOTECHNOLOGY </li></ul><ul><li>SINDH AGRI UNIVERSITY TANDO JAM </li></ul>
  3. 4. PRESERVATION <ul><li>Microbes eat the same foods we do! </li></ul><ul><li>Controlled microbial growth can enhance our diets and help preserve foods </li></ul><ul><li>Metabolism of some microbes leads to spoilage of foods </li></ul><ul><li>Some microbes in food are pathogens </li></ul><ul><li>Minimizing microbial contamination of food is a priority </li></ul>
  4. 5. <ul><li>Pr-industrial </li></ul><ul><li>Drying </li></ul><ul><li>Pickling (salting) </li></ul><ul><li>Canning </li></ul><ul><li>Mass production </li></ul><ul><li>Pasteurization </li></ul><ul><li>Preservatives </li></ul><ul><li>Freezing (freeze-drying) </li></ul><ul><li>Irradiation </li></ul>Food preservation
  5. 6. Preservation <ul><li>Chemical and Modified atmosphere process </li></ul><ul><li>Physical process </li></ul><ul><li>Food Microbiology </li></ul>
  6. 7. Chemical Preservative <ul><li>Sodium Benzoate </li></ul><ul><li>Sorbet </li></ul><ul><li>Proprionates </li></ul>
  7. 8. <ul><li>Salt </li></ul><ul><li>Sugar </li></ul><ul><li>Spices and Essential Oils </li></ul><ul><li>Flavoring Agents </li></ul><ul><li>Fatty acids </li></ul>Chemical Preservatives
  8. 9. Modified Atmosphere Preservation <ul><li>MAP – Modified Atmosphere PRESERVATION </li></ul><ul><li>Carbon Dioxide is mostly used </li></ul><ul><li>Types </li></ul><ul><li>Hypobaric </li></ul><ul><li>Vacuum Packaging </li></ul><ul><li>MAP </li></ul><ul><li>Equilibrium Modified Atmosphere </li></ul><ul><li>Controlled Atmosphere Packaging </li></ul>
  9. 10. Food preservation <ul><li>• The most important types of </li></ul><ul><li>commercial drying are: </li></ul><ul><li>– Conventional: heat. </li></ul><ul><li>– Vacuum: pulls the water out. </li></ul><ul><li>– Osmotic: water drawn out by osmosis. </li></ul><ul><li>– Freeze-drying: ice crystals </li></ul><ul><li>vaporize . </li></ul>
  10. 11. Food preservation To preserve food through the use of salt and drying. Sugar, spices, or nitrates may also be added.
  11. 12. PHYSICAL PRESERVATION <ul><li>Low Temperature </li></ul><ul><li>refrigeration at 5 °C retards but does not stop microbial growth. </li></ul><ul><li>microorganisms can still cause spoilage with extended spoilage </li></ul><ul><li>growth at temperatures below -10 °C has been observed </li></ul>
  12. 13. <ul><li>Radiation </li></ul><ul><li>ultraviolet (UV) radiation </li></ul><ul><li>used for surfaces of food-handling equipment </li></ul><ul><li>does not penetrate foods </li></ul><ul><li>Radappertization ; </li></ul><ul><li>use of ionizing radiation (gamma radiation) to extend shelf life or sterilize meat, sea foods, fruits, and vegetables </li></ul><ul><li>kills microbes in moist foods by producing peroxides from water </li></ul><ul><li>peroxides oxidize cellular constituents </li></ul>
  13. 14. <ul><li>Canning </li></ul><ul><li>food heated in special containers (retorts) to 115 ° C for 25 to 100 minutes </li></ul><ul><li>kills spoilage microbes, but not necessarily all microbes in food </li></ul><ul><li>leakage of contaminated water into cans during process may cause contamination. </li></ul>
  14. 15. <ul><li>Pasteurization </li></ul><ul><li>kills pathogens and substantially reduces number of spoilage organisms </li></ul><ul><li>different pasteurization procedures heat for different lengths of time </li></ul><ul><li>shorter heating times result in improved flavor </li></ul>
  15. 16. Isolation Technique <ul><li>Naturally, microbial cultures are mixed. </li></ul><ul><li>Identification relies upon isolating individual colonies </li></ul><ul><li>Testing requires pure cultures </li></ul><ul><li>As a result isolation technique provides an essential microbiological tool </li></ul>
  16. 17. Mixed Culture from Raw Poultry
  17. 18. Streak Plate Isolation Principle
  18. 19. Streak Plate Isolation Principle <ul><li>An original inoculum containing a mixture of bacteria is spread into 4 quadrants on solid media. </li></ul><ul><li>The goal is to reduce the number of bacteria in each subsequent quadrant. </li></ul><ul><li>Colonies are masses of offspring from an individual cell therefore streaking attempts to separate individual cells. </li></ul><ul><li>Discrete colonies form as the individual cells are separated and then multiply to form isolated colonies in the later quadrants </li></ul>
  19. 20. Streak Plate Isolation
  20. 21. Can an isolated colony be considered pure? <ul><li>This is generally assumed, however…. </li></ul><ul><li>some colonies are very slow growers and may be too small to see. </li></ul><ul><li>some colonies may be growing under another colony </li></ul><ul><li>selective media may be preventing reproduction of some bacteria so they may be present but not visible </li></ul><ul><li>condensed water, capsules, slime, all represent areas where individual contaminant cells hide out. </li></ul>
  21. 22. Isolation Requires Aseptic Technique
  22. 23. Isolation Requires Aseptic Technique <ul><li>Aseptic technique is the process of: </li></ul><ul><li>Preventing contamination of a culture with environmental microbes </li></ul><ul><li>Preventing contamination of yourself or the environment with the organism in the culture </li></ul><ul><li>Remember everything is contaminated with a variety of environmental microbes. </li></ul><ul><li>Remember microbes are invisible, you must “see with your minds eye” during these procedures . </li></ul>