MadSci Network: Microbiology

Re: Why is wet heat more effecitve than dry heat in sanitization?

Date: Tue Jul 19 07:29:19 2005
Posted By: Edward Richter, Faculty, Food Microbiology
Area of science: Microbiology
ID: 1118976305.Mi

Wet heat (steam) has much greater penetration efficiency than dry heat. The heat transfer rate is higher with wet heat as compared with dry heat. Moisture conducts heat better than air. When you subject something to heat such as a beef roast in the oven. The roast starts off cold even though you have pre heated the oven. The air surrounding the meat is hot but the roast remains cool. Gradually the heat of the surrounding air raises the temperature of the roast. Eventually they will come to equilibrium (become equal). This would result in a burnt roast. Typically we would like the inside of the roast to become 140- 145F even though we cook in a 350F oven. The larger the roast the longer it will take the dry heat to raise the internal temperature. As long as there is water in food the temperature can not rise above boiling 212F. Once the moisture has been evaporated the food can rise in temperature. If we cook the same roast in a pressure cooker, we will see the internal temperature rise much quicker. The higher the pressure the greater the penetration

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