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