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Food Spoilage

Food Spoilage. What is Food Spoilage. Spoilage is a natural phenomenon. It occurs at varying rates depending on the storage temperature, kind of food involved, kind of microorga- nisms present, packaging materials used, food additives used and method of preservation.

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Food Spoilage

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  1. Food Spoilage

  2. What is Food Spoilage Spoilage is a natural phenomenon. It occurs at varying rates depending on the storage temperature, kind of food involved, kind of microorga- nisms present, packaging materials used, food additives used and method of preservation.

  3. Spoiled Food can be defined as any food that is not acceptable to an individual or group because of health hazard or aesthetic appeal.

  4. The period of time between the manufacture and the retail purchase of food is called the Shelf Life. During this time a food product has a satisfactory quality in terms of nutritional value, taste, texture and appearance

  5. Food categories • Stable or Nonperishable Foods • Semi-perishable Foods • Perishable Foods

  6. PRE-HARVEST DETERIORATION • 10-20% AGRICULTURAL COMMODITIES ARE LOST • WEEDS • INSECTS • MICROORGANISMS • RODENTS • BIRDS

  7. Conditions Leading to Food Decay EXTERNAL CONDITIONS PRODUCT CONDITIONS Storage temperature Initial quality Humidity Raw material Gas O2, N2, CO2 Ingredients Packaging materials Intrinsic factors Light Hygienic Processing BIOCHEMICAL/CHEMICAL DECAY MICROBIAL DECAY Rancidity Putrid flavor WOF Sour taste Changes in texture Slime, Gas Discoloration Off-flavors Loss od nutrients Formation od toxic substances Changes in texture

  8. Causes of Food Spoilage: • Senescence • Microbial decay • Chemical deterioration (enzymatic & non-enzymatic) • Physical deterioration; desiccation. • Insects and rodents

  9. SENESCENCE • FRUITS & VEGETABLES CONTINUE TO RESPIRE AFTER HARVEST LEADING TO DETERIORATION • CATABOLIC REACTIONS IN MEAT & FISH

  10. Enzymatic spoilage Enzymes are chemicals produced by all living things. They help speed up or slow down chemical reactions, act as transports for foods, and are a normal constituent of foods. For instance, as a banana matures, the color changes from green to yellow to brown to black. The change is caused by the enzymes (chemicals) in the banana. The ripening, then softening, of other fruits such as apples, peaches and tomatoes is another example of enzymatic action.

  11. Enzymatic spoilage Enzymes can be inactivated by heat, which is the reason for blanching vegetables; or they can be inactivated by cold temperatures below 40 degrees F, which is the reason for placing vegetables under refrigeration. Think of green tomatoes in the refrigerator compared to tomatoes sitting on the window sill. Bacteria also produce enzymes that break down food and allow them to obtain nutrients through their cell walls. Therefore, lowering the temperature reduces the rate of enzyme action as well as the rate at which bacteria can multiply.

  12. Examples: • In corn and pea: simple sugar starch • In vegetables and fruits phenol + O2 brown products • In butter fat hydrolysed fat

  13. Physical Deterioration & Dessication • PHYSICAL/MECHANICAL ABUSE CAUSES • RELEASE OF ENZYMES INTO TISSUES • CRUSHING, BREAKS IN THE SKIN (FRUIT/ • VEGETABLE) LEAD TO MICROBIAL INVASION • WATER/MOISTURE LOSS DURING STORAGE • WATER/MOISTURE UPTAKE • RETROGRADATION OF STARCH • MELTING OF FOOD

  14. Microbial Decay • Bacteria • Yeasts • Molds • Viruses

  15. BACTERIA • GROW THE FASTEST • REPRODUCE BY CELL DIVISION: • VEGETATIVE CELLS (actively metabolizing cells, • consume nutrients and produce waste products) • SPORES (dormant form of the bacterial cell) • BASIC SHAPES: • • COCCI (CIRCULAR SHAPE) • • RODS (LENGTH IS GREATER THEN WIDTH) • • MOTILE RODS (FLAGELLA)

  16. Yeasts ; Molds • YEASTS • COMMONLY FOUND IN MANY FOODS • GROWTH IS SLOWER • TOLERATE SEVERE ENVIRONMENTAL CONDITIONS (pH, aw) • SOME ARE USED TO PRODUCE FERMENTED FOODS • MOLDS • FILAMENTOUS FORM • FOUND IN MOST FOODS • TOLERATE HARSH ENVIRONMENTAL CONDITIONS (pH, aw) • SOME USED IN FERMENTED FOODS • AGENTS OF FOOD SPOILAGE • PRODUCE TOXINS (MYCOTOXINS) • PRODUCE SPORES

  17. MICROORGANISMS CAN BE CHARACTERIZED ON THE BASIS OF OXYGEN REQUIREMENTS • AEROBES • GROW ONLY IN THE PRESENCE OF O2 • ANAEROBES • GROW ONLY IN THE ABSENCE OFO2 • FACULTATIVE ANAEROBE • CAN GROW IN THE PRESENCE/ABSENCE OF O2 • BACTERIA: Aerobes, anaerobes, facultative anaerobes • YEASTS are facultative anaerobes • MOLDS are strictly aerobes

  18. Conditions Necessary for Microbial Decay Microbial spoilage is the major cause of food spoilage. It occurs as a result of contamination of food by microorganisms, provision of a suitable environment for their growth, and degradation of the foodstuffs. To control microbial build up, you must control: • The source of microorganisms - people, raw materials, equipment, air currents, dust and pests. • Food residues, which are required for bacterial growth

  19. • Moisture is required for growth; thus relative humidity should be monitored. • Time during which food product is exposed to a given set of conditions that promote bacterial growth. • Temperature determines the kind of microorganisms. Conditions Necessary for Microbial Decay

  20. Microbial Growth Curve A-B lag phase B-C phase of positive acceleration C-D exponential phase D-E phase of negative acceleration E-F stationary phase F-G accelerated death phase G-H death phase H-I survival phase

  21. The best way to prevent microbial food decay is to lengthen: • The lag phase • The phase of positive growth

  22. This can be accomplish by: • Reducing the amount of microbial contamination as much as possible • Avoiding the addition of actively growing organisms

  23. Microbial decay can be prevented by: • Keeping out microorganisms • Removal of microorganisms • Hindering the growth or activity of microorganisms • Killing the microorganisms

  24. Self-decomposition of food can be prevented by: • by destruction or inactivation of food enzymes • by prevention or delay of purely chemical reactions

  25. Classification of food preservation methods based on major controlling factors • high temperature • low temperature • removal or tying up moisture • addition of chemical preservatives • keeping microorganisms out • ionizing radiation (irradiation)

  26. The kinds and numbers of microorganisms present on or in food depends on: • The kind and extent of contamination • Previous opportunities for the growth of certain kinds • Pre-treatments which food has received

  27. Factors affecting microbial growth • Associative Growth: Antibiotic, Symbiotic, Metabiotic • Environmental Conditions: • Physical State of Food • Chemical State of Food • Temperature

  28. Chemical Changes caused by microorganisms: • Changes in nitrogenous organic compounds. • Anaerobic decomposition of proteins, peptides and amino acids that result in production of obnoxious odorous is called Putrefaction.

  29. Changes in carbohydrates: • Alcoholic fermentation • Lactic fermentation • Mixed lactic fermentation • Coliform type fermentation • Propionic fermentation • Butyric-butyl-isopropyl fermentation

  30. Changes in organic acids • Changes in lipids • Other changes

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