What’s that got to do with food? Well, food is the body’s basic source of energy, its fuel! Physiologists and nutritionists use kilocalories (kcal) to let us know how much energy our food contains. Let’s say your diet intake is 2400 Calories/day. Notice the big “C” in calorie. A food calorie or “Calorie”—the one you read about on packaged food products and in articles about nutrition—is the same as a kcal. So, if you consume 2400 Calories/day, you’re also consuming 2400 kcal/day. Now, one kcal is equivalent to 4184 joules or 4184 J, the SI unit for energy. Power is given in joules per second (J/s) or watts (W). What all this means is that your daily diet represents about 1 x 107 J/day, and since a day has 86,400 seconds, your average power is about 115 W, a little more than a 100 W light bulb.
How powerful are you if you eat four Cinnabons? One Cinnabon contains 2000 Calories.
Cameron, John R., Skofronick, James G., and Grant, Roderick M. Physics of the Body (Second Edition). Madison, Wisconsin: Medical Physics Publishing, 1999.
Thursday, March 26, 2009
Tuesday, March 17, 2009
How Long Can I Store This Food In The Freezer?
In the winter time across the country, especially in the Midwest and Northeast, people sprinkle salt on icy sidewalks and roads to help “melt the ice,” essentially lowering the freezing point of the ice-water system. So, instead of the ice freezing at 0°C, it might not freeze until it’s -6°C or colder—a good thing when winter’s temperatures drop below freezing!
Now what about food that’s been salted, particularly prepared food that will be stored frozen? The prepared food won’t freeze until it’s reached a much lower temperature than if it had been unsalted and will thus have a shorter minimum freezer storage life. If there’s lots of salt in the food, it could take very low temperatures to freeze the food, and, again, decrease the food’s freezer storage life.
Now, fat does not freeze as well as protein or carbohydrate and consequently has a shorter freezer storage life than its two companion nutrients. The implication is clear: If you plan to freeze a cut of meat for a long period, you should probably trim off all or most of its excess fat before freezing it.
How about salt pork and bacon? Both are salty and fatty, depressing their freezing points and making their freezing properties “poor.” Consequently, salt pork and bacon have a short freezer storage life.
Consider ice cream. It is foam that is preserved by freezing. It contains solid globules of milk, fat, tiny air pockets, minute ice crystals, and small droplets of liquid water containing dissolved sugars and salts with suspended milk proteins or lots of solutes! The droplets of water solution do not freeze because of their high concentration of solutes (like the salt on icy sidewalks or in food). Can you see why ice cream goes “bad” or “tastes funny” after a short while in the freezer?
If you want to know the science behind this, take a peek in a chemistry reference under colligative properties. Freezing point depression is just a colligative property of solutions; it is characteristic of the solvent and depends on the concentration, not the nature of the solute.
Look in your freezer. Ask yourself the question, “How long has this (food) been in here?” Then, think about what’s in that food.
Dorin, H., Demmin, P., and Gabel, D. Chemistry: The Study of Matter (Fourth Edition). Englewood Cliffs, New Jersey: Prentice Hall, Inc., 1992.
Hillman, Howard. The New Kitchen Science. New York: Houghton Mifflin Company, 2003.
Now what about food that’s been salted, particularly prepared food that will be stored frozen? The prepared food won’t freeze until it’s reached a much lower temperature than if it had been unsalted and will thus have a shorter minimum freezer storage life. If there’s lots of salt in the food, it could take very low temperatures to freeze the food, and, again, decrease the food’s freezer storage life.
Now, fat does not freeze as well as protein or carbohydrate and consequently has a shorter freezer storage life than its two companion nutrients. The implication is clear: If you plan to freeze a cut of meat for a long period, you should probably trim off all or most of its excess fat before freezing it.
How about salt pork and bacon? Both are salty and fatty, depressing their freezing points and making their freezing properties “poor.” Consequently, salt pork and bacon have a short freezer storage life.
Consider ice cream. It is foam that is preserved by freezing. It contains solid globules of milk, fat, tiny air pockets, minute ice crystals, and small droplets of liquid water containing dissolved sugars and salts with suspended milk proteins or lots of solutes! The droplets of water solution do not freeze because of their high concentration of solutes (like the salt on icy sidewalks or in food). Can you see why ice cream goes “bad” or “tastes funny” after a short while in the freezer?
If you want to know the science behind this, take a peek in a chemistry reference under colligative properties. Freezing point depression is just a colligative property of solutions; it is characteristic of the solvent and depends on the concentration, not the nature of the solute.
Look in your freezer. Ask yourself the question, “How long has this (food) been in here?” Then, think about what’s in that food.
Dorin, H., Demmin, P., and Gabel, D. Chemistry: The Study of Matter (Fourth Edition). Englewood Cliffs, New Jersey: Prentice Hall, Inc., 1992.
Hillman, Howard. The New Kitchen Science. New York: Houghton Mifflin Company, 2003.
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