Difference between revisions of "Cooking Time and Temperature"

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Revision as of 01:58, 11 August 2013

Ingesting the wrong E. Coli bacteria can ruin your picnic. And your kidneys.

As the food we cook is generally meant to be fed to humans, making sure it is safe for consumption is important. Heating food to destroy harmful bacteria is a common way to reduce risk for foodborne illness. Controlling cooking time and temperature allow a cook to maintain acceptable safety while causing minimum damage to food texture and taste.

Background

There are two types of foodborne illness: infection and food poisoning.

Infection occurs when microorganisms directly penetrate the body and grow. Sometimes these organisms can also secrete toxins. Examples include salmonella, trichinella spiralis, E. coli (certain strands), Listeria monocytogenes, and prions like BSE (mad cow). Noninvasive infection primarily involve organisms such as the tapeworm that live inside humans and, while there, secrete toxins that do damage.

Food poisoning is caused by toxins already in the food. This causes the most rapid onset of symptoms (1-6 hours) as toxins are already present and no infection needs to happen. Examples include C. botulinum, Salmonella and Staphyloccus aureus.

The possibility of symptoms from both bacteria and their toxins is why we cannot leave meat sitting in our refrigerator for too long, cook it to a "recommended temperature", and then still eat it. We could kill the active microorganisms but their toxins wouldn't go away. Foodborne illness happens on many different foods, but most people don't cook things like vegetables to make them safe. As a result, this entire guide will focus on the other problem of killing bacteria before they have already contaminated meats.

Time and Temperature

Pasteurization depends on time and temperature. As temperature increases from freezing, bacteria thrive and multiply more rapidly up to a point where they start dying. For example, each 15.2 minutes at 130 degrees Fahrenheit kills 90% of intact Salmonella bacteria. At 140 degrees Fahrenheit, this happens every 2.76 minutes. Each time this 90% killing happens is called a decade reduction. So a 2D reduction is 99%, a 99.99% reduction is 4D, and so on. If that 15.2 minute reduction is 1D, then a 5D reduction would take 15.2x5 or 76 minutes, killing off 99.999% of bacteria.

General FDA recommendations for fresh food are to reach a reduction level of 6.5D, or 99.99997% of pathogens present. When we're cooking on the stovetop or in the oven, there is no way to have this level of control over keeping the food at a particular temperature throughout much less time its holding for pathogen reduction against the guidelines. When we cook sous vide, however, we can estimate the time it takes even the center of the food to reach a temperature, and hold it at a pasteurization temperature to achieve the recommended guidelines.

Cooking Charts and Tables

Extended and Simplified 6.5D Salmonella Reduction Table
°Celsius °Fahrenheit Time
52 125.6 5h 14m
52.2 126 4h 46m
52.8 127 3h 48m
53 127.4 3h 28m
53.3 128 3h 1m
53.9 129 2h 24m
54 129.2 2h 17m
54.4 130 1h 54m
55 131 1h 31m
55.6 132 1h 12m
56 132.8 1h
56.1 133 57m 31s
56.7 134 45m 44s
57 134.6 39m 51s
57.2 135 36m 22s
57.8 136 28m 55s
58 136.4 26m 23s
58.3 137 23m
58.9 138 18m 17s
59 138.2 17m 28s
59.4 139 14m 32s
60 140 11m 34s
60.6 141 9m 12s
61 141.8 7m 39s
61.1 142 7m 19s
61.7 143 5m 49s
62 143.6 5m 4s
62.2 144 4m 37s
62.8 145 3m 41s
63 145.4 3m 21s
63.3 146 2m 55s
63.9 147 2m 19s
64 147.2 2m 13s
64.4 148 1m 51s
65 149 1m 28s
65.6 150 1m 10s
66 150.8 58s
66.7 152 44s
67 152.6 39s
67.8 154 28s
68 154.4 26s
68.9 156 18s
70 158 11s
71.1 160 7.1s
72.2 162 4.5s
75 167 1.4s
76.7 170 0.7s
77 170.6 0.6s
79.4 175 0.23s
80 176 0.18s
82.2 180 0.07s
85 185 0.02s

See Also

References

  • Mhyrvold, Nathan et al. Modernist Cuisine: The Art and Science of Cooking. Bellevue, Wash.: Cooking Lab, 2011. ISBN 9780982761007. Vol. I pages 110-112, 192-194.
  • Baldwin, Douglas E. Sous Vide For the Home Cook. Incline Village, Nev.: Paradox Press, 2010. ISBN 978-0-9844936-0-9