The pH of a food affects the emergence of Clostridium botulinum from spores during storage. This impacts how much processing is required when canning.
pH
Acidity of Food
<= 4.6
high
> 4.6
low
Examples of high acidity foods:
(1) pickles, salsa or other items in vinegar (acidified foods)
(2) most fruits
(3) jams and jellies
(4) yogurt
(5) most barbacue sauces
Examples of low acidity foods:
(1) most vegetables
(2) meat and poultry
(3) milk
(4) most cheeses
High acidity foods:
(1) require heating to the pasteurization temperature for several minutes
(2) do not require pressure cooking or prolonged cooking
(3) may be spoiled if there is growth of yeast or mold if not heated high enough for long enough (the growth of a fungus may raise the pH high enough for spores to germinate, resulting in botulism)
pH
Pasteurization Temperature
<= 3.5
79.5°C (175°F)
3.5 to 4.0
85°C (185°C)
4.0 to 4.3
90.5°C (195°C)
4.3 to 4.5
99°C (210°F)
The processing of high acidity foods do not eliminate spores of Clostridium botulinum.
Low acidity foods require pressure cooking at high temperatures (> 115.6°C, > 240°F) for prolonged periods (from 20 minutes to several hours). Companies preparing commercial products must register with the FDA.
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