Pozzi Homefoodpreservation

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Pozzi Homefoodpreservation

  1. 1. HOME FOOD PRESERVATION A BIOLOGICAL OVERVIEW
  2. 2. TO OBTAIN HOME CANNED FOOD... <ul><li>We must deactivate the enzymes that break down proteins and spoil food </li></ul><ul><li>We must kill all the microorganisms that coagulate proteins and stop them from developing </li></ul><ul><li>STERILIZATION </li></ul>
  3. 3. STERILIZATION DESTROYS SPORES <ul><li>STERILIZATION TEMPERATURES: </li></ul><ul><li>Food pH < 4.5 100°C </li></ul><ul><li>(acid food) </li></ul><ul><li>Food pH > 4.5 115/120°C for at least 20 minutes </li></ul>
  4. 4. <ul><li>ENZYMES </li></ul><ul><li>proteins that denaturate at high temperatures. </li></ul><ul><li>They get deactivated in a few minutes when exposed to temperatures in between 50°C and 80°C </li></ul><ul><li>MICROORGANISMS </li></ul><ul><li>particularly sensitive to humid heat, that tends to coagulate proteins. </li></ul><ul><li>The most resistant are the sporeformers like Clostridium botulinum that can resist in humid heat conditions for 20 minutes at 120°C (while the other bacteria usually die after 10 minutes of exposure at 60-70°C heat) </li></ul>
  5. 5. WHAT IS BOTULINUM? <ul><li>Botulinum is a type of bacteria from the clostridium family that produces a poisonous toxin in anaerobic environmental conditions </li></ul><ul><li>In environmental stressed situations this kind of bacteria turns into spores that can resist in this form until the environment conditions get better </li></ul>
  6. 6. THE SPORES <ul><li>Spores are present in all fresh food but do not develop with oxigen </li></ul><ul><li>When you can food though, the spores start germinating if they haven’t been entirely destroyed </li></ul><ul><li>They are not responsible for the intoxication directly but release a toxin in the environment while growing </li></ul>
  7. 7. THE TOXIN <ul><li>The toxin is produced in about 3-4 days and is one of the strongest poison we know </li></ul><ul><li>It is a protein that acts like a neurotoxic and blocks the transmission of nervous impulses </li></ul><ul><li>The toxin, differently from the bacteria, does not resist to heat and can be destroyed in 20 minutes when exposed to 80°C heat </li></ul>
  8. 8. CONDITIONS WHERE BOTULISM GROWS <ul><li>Humid food </li></ul><ul><li>Food with pH > 4.5 </li></ul><ul><li>Temperature in between 3°C and 50°C </li></ul><ul><li>Salt concentration < 10% </li></ul><ul><li>Sugar concentration < 35% </li></ul>
  9. 9. WHAT TYPE OF FOOD IS EXPOSED TO RISK OF BOTULISM? <ul><li>Oils aromatized with humid and not enogh acidic products (garlic, fresh herbs, hot chili pepper, ginger...) </li></ul><ul><li>Humid, not enogh acidic and not enough salted foods that have been jarred, put in vacuum or under oil (all vegetables unless they are first put into acidic solutions, certain types of fresh fruit with a very high pH such as figs, meat, fish, humid and smoked foods) </li></ul><ul><li>Cured encased meat </li></ul>
  10. 10. <ul><li>FOOD WITH HIGH ACIDITY (Ph < 4.5) </li></ul><ul><li>(Low risk food when it comes to preservation) </li></ul><ul><li>Apples </li></ul><ul><li>Cherries </li></ul><ul><li>Lemon juice </li></ul><ul><li>Peaches </li></ul><ul><li>Pears </li></ul><ul><li>Pickled food </li></ul><ul><li>Tomatoes juice </li></ul><ul><li>Orange juice </li></ul><ul><li>FOOD WITH LOW ACIDITY (Ph > 4.5) </li></ul><ul><li>(Low risk food when it comes to preservation) </li></ul><ul><li>Asparagus </li></ul><ul><li>Beans </li></ul><ul><li>Carrots </li></ul><ul><li>Figs </li></ul><ul><li>Mushrooms </li></ul><ul><li>Potatoes </li></ul><ul><li>Spinach </li></ul>
  11. 11. <ul><li>Food which is enough acidic, salty and/or with an optimum percentage of sugar does not require special treatments and attentions when jarred </li></ul>
  12. 12. ACIDIFICATION to prevent microbial activity <ul><li>VINEGAR </li></ul><ul><li>can be used as acidic agent in home canning thank to the acetic acid which must never be below 6% </li></ul><ul><li>pH decreases and the toxicity of acetic acid acts against the micro-organisms </li></ul>
  13. 13. OIL must always be associated to other preserving methods because is not a preservative itself
  14. 14. HOW DO I RECOGNIZE A SPOILED CANNED FOOD? <ul><li>Check the top of the jar and if the air volume increased in the jar or the top was not properly closed the food may be spoiled </li></ul><ul><li>Check if there is some food on the external part of the jar that came out from the top </li></ul><ul><li>Check if there are not air bubbles that come to the surface of food or there are not changing in the color of food </li></ul><ul><li>Once opened smell the food and make sure there are not moulds </li></ul>

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