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Factors affecting survival and growth

Factors affecting survival and growth. FS0501 1. 2000. Traditional food preservation. - Stored in cool caves. Cheese, fruits, vegetables. - Frozen / freeze-dried at. Meat (Switzerland),. high latitudes and altitudes potato (Peru). - Dried in the sun. Tomato (Italy),.

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Factors affecting survival and growth

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  1. Factorsaffectingsurvival andgrowth FS0501 1 2000

  2. Traditionalfoodpreservation - Stored in cool caves Cheese, fruits, vegetables - Frozen / freeze-dried at Meat (Switzerland), high latitudes and altitudes potato (Peru) - Dried in the sun Tomato (Italy), fish, meat (South America), Biltong (South Africa) - Smoked / dried over fires - Salted and dried Kipper (UK, smoked herring) Bacalhau (Portugal - dried cod) - Fermented Tempeh, cheese, wine, beer, yoghurt, kefir FS0501 2 2000

  3. Pasteur’sgermtheory Traditional methods work by ‹ Preventing contamination ‹ Destroying microorganisms ‹ Inhibiting growth of undesirable microorganisms FS0501 3 2000

  4. Traditionalfoodpreservation Traditional preservation sometimes fails to preserve the food, or to kill the pathogens. In these cases, spoilage or food poisoning may occur. Examples: salmonellosis from dried beef (Salmonella St. Paul ) and poisoning from tempehbonkrek in Indonesia. FS0501 4 2000

  5. Traditionalfoodpreservation Certain “traditional” foods can be manufactured using industrial processes Example: Soy sauce FS0501 5 2000

  6. Factorsaffectinggrowthof bacteriainfood - Temperature - Time - pH - Water activity (aw) - Oxygen tension - Preservatives - Microbial interactions FS0501 6 2000

  7. Temperature Boiling point 100° SAFETY Pasteurising temperature 72° 60° Body temperature DANGER 36.5° Fridge 10° 0° SAFETY Freezer FS0501 7 2000

  8. Howtemperatureaffects growthrateofabacterialpopulation B (Optimum) C (Minimum) A (Maximum) Cold Hot Temperature FS0501 8 2000

  9. GrowthofS.typhimurium atdifferenttemperatures 9 8 7 25° 20° 6 15° 5 10° 4 3 2 1 0 0 1 2 3 4 5 Time (Days) FS0501 9 2000

  10. Temperaturerange forgrowthofpathogens Temperature°C Min. Opt. Max. Salmonella 5 35 - 37 47 Campylobacter 30 42 47 E. coli 10 37 48 S. aureus 6.5 37 - 40 48 C. botulinum (proteolytic) 10 50 C. botulinum (non-proteolytic) 3.3 25 - 37 B. cereus 4 30 - 35 48 - 501 432 FS0501 10 2000

  11. Temperaturerangeforgrowth oftoxigenicmoulds Temperature °C Min.Opt.Max. Penicillium verrucosum Aspergillus ochraceus Aspergillus flavus 0 20 31 8 28 37 10 32 42 3 25 37 Fusarium moniliforme FS0501 11 2000

  12. Growthofdifferentbacteriaat25°C 9 8 7 6 S. typhimurium 5 L. monocytogenes Ps. fluorescens Log 4 CFU B. cereus 3 C. bot-Proteolytic 2 G+ve Spoilers 1 0 0 1 2 3 4 Time (Days) FS0501 12 2000

  13. Effectoftemperatureontime tobotulinumtoxinproduction 10 9 8 Vacuum-packed hot smoked trout 7 6 Salt concentration = 0.5% 5 4 3 2 1 0 0 5 10 15 20 25 Temperature (°C) FS0501 13 2000

  14. Temperatureaffectsbacteria ‹ Lag phase ‹ Growth rate ‹ Final cell numbers through the change in ‹ Enzymatic and chemical composition of cells ‹ Nutritional requirements ‹ Limits for other factors influencing growth FS0501 14 2000

  15. Effectofsaltconcentrationon time to botulinum toxin production 16 14 12 10 10°C 14°C 18°C 24°C 8 6 4 2 0 0 0.5 1 1.5 2 Salt Concentration (%) FS0501 15 2000

  16. LimitsofpHforgrowthofpathogens pH Min Max. Escherichia coli 4.4 8.5 Salmonella typhi 4 - 4.5 8 - 9.6 Bacillus cereus 4.9 9.3 Clostridium botulinum 4.6 8.5 Staphylococcus aureus 4 9.8 Saccharomyces cerevisiae 2.3 8.6 Aspergillus flavus 2.0 11.2 Fusarium moniliforme 2.5 10.7 Penicillium verrucosum 2.0 10.0 FS0501 16 2000

  17. Definitionofwateractivity(aw) aW = p / po aw is the ratio of the water vapourpressure of the food (p) to that of pure water (po) at the same temperature. FS0501 17 2000

  18. Effectofwateractivityonlagtime of S.aureusinUHTmilkat12°C 120 100 80 60 40 20 0.93 0.94 0.95 0.96 0.97 0.98 Water activity (a w) FS0501 18 2000

  19. NaClandglucoseconcentrationsand correspondingawvaluesat25°C aW % w/w % w/w NaCl Glucose 1.00 0.00 0.00 0.99 1.74 8.90 0.98 3.43 15.74 0.96 6.57 28.51 0.94 9.38 37.83 0.92 11.90 43.72 0.90 14.18 48.54 0.88 16.28 53.05 0.86 18.18 58.45 FS0501 19 2000

  20. MinimumlevelsofaWpermittinggrowth atnearoptimumtemperatures aW Moulds Aspergillus chevalieri 0.71 Aspergillus ochraceus 0.78 Aspergillus flavus 0.80 Penicillium verrucosum 0.79 Fusarium moniliforme 0.87 Yeasts Saccharomyces rouxii 0.62 Saccharomyces cerevisiae 0.90 Bacteria Bacillus cereus 0.92 Clostridium botulinum (proteolytic) 0.93 Clostridium botulinum (non-proteolytic) 0.97 Escherichia coli 0.93 Salmonella 0.95 Staphylococcus aureus 0.83 FS0501 20 2000

  21. RangeofaWinfoods andtheirmicrobialflora aw range foods microbial flora Fresh meats Fresh fish Fresh fruits (C. perfringens, Salmonella) Fresh vegetables Canned vegetables > 0.98 in brine Canned fruit in light syrup (Pseudomonas) (<3.5% salt, 26% sugar) Fermented sausages Processed cheese Bread 0.93 - 0.98 (B. cereus, C. botulinum, Salmonella) Evaporated milk Tomato paste lactobacilli, bacilli and micrococci (10% salt, 50% sugar) FS0501 21 2000

  22. RangeofaWinfoods andtheirmicrobialflora aw range foods microbial flora S. aureus Dry fermented sausages 0.85 - 0.93 Mycotoxin Raw ham (17% salt, producing moulds Spoilage yeasts saturated sucrose) and moulds Dried fruit Flour Xerophilic fungi 0.6 - 0.85 Cereals Salted fish Nuts Halophiles Osmophilic yeasts Confectionery Honey No growth but may remain viable < 0.6 Noodles Dried egg, milk FS0501 22 2000

  23. Factorsaffectingmicrobialgrowth Keymessages Temperature, pH, water activity and oxygen tension are the principal factors affecting microbial growth There are optimum ranges for these parameters These optima are interdependent They can be selected to inhibit the growth of certain organisms within limits related to the palatability of food Certain foods are suited for the growth of certain flora FS0501 23 2000

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