|SCIENCE OF FOOD AND COOKING|| |
-- Egg whites begin to thicken
158°F/70°C-- Egg yolks set.
165°F/73°C-- Whole egg sets. If eggs are cooked at 212F for too long they get rubbery as proteins continue to coagulate and water is pushed out from between protein molecules.
NOTES: Egg white contains approximately 40 different proteins with Ovalbumin (54%), and Ovotransferrin 12% being the major components. Ovalbumin begins to set at 180°F/80C while Ovotransferrin only begins to set when heated to 140°F/60C. Egg yolks contain lipoproteins which coagulate at about 158°F.
If eggs are cooked at 212°F for too long they will just get rubbery as proteins continue to coagulate and water gets pushed out from between protein molecules.
Keep in mind salmonella is killed instantly when subjected to a temperature of 165° F.
120°F/50°C -- Meat develops a white opacity as heat sensitive myosin denatures. Coagulation produces large enough clumps to scatter light. Red meat turns pink.
140°F/60°C -- Red myoglobin begins to denature into tan colored hemichrome. Meat turns from pink to brown-grey color.
140°F/60°C -- Meat suddely releases lots of juice, shrinks noticebly, and becomes chewy as a result of collagen denaturing.
160°F/70°C -- Connective tissue collagen begins to dissolve to gelatin.
NOTES: At 140°F changes are caused by the denaturing of collagen in the cells. Meat served at this temperature med-rare is changing from juicy to dry. At 160°F/ 70°C connective tissue collagen begins to dissolve to gelatin. This however is a very lengthy process. The fibers are still stiff and dry but meat seems more tender. Source: Harold McGee -- On Food and Cooking
BREAST MEAT IN POULTRY
158°F /70°C -- Breast meat in birds gets dry as collagen contracts and meat gets tougher.
165°F/ 73°C -- Leg meat is full of connective tissue and is chewy if cooked below this temperature.
NOTES: Collagen (fibrous protein constituting a good part of meat) contracts and gets tougher over 70°C/158°F. Thus, the tip is to cook below this temperature to keep the meat tender for breast meat.
ABOUT SUGARS AND CARAMELIZATION
Caramelization or caramelisation (see spelling differences) is the oxidation of sugar, a process used extensively in cooking for the resulting nutty flavor and brown color. Caramelization is a type of non-enzymatic browning reaction. As the process occurs, volatile chemicals are released producing the characteristic caramel flavor. The reaction involves the removal of water (as steam) and the break down of the sugar. The caramelization reaction depends on the type of sugar. Sucrose and glucose caramelize around 160C (320F) and fructose caramelizes at 110C (230F).
Caramelization temperatures Sugar Temperature
Fructose 110° C, 230° F
Galactose 160° C, 320° F
Glucose 160° C, 320° F
Maltose 180° C, 356° F
Sucrose 160° C, 320° F
The highest rate of the color development is caused by fructose as caramelization of fructose starts at 110C. Baked goods made from honey or fructose syrup will therefore give a darker color. Source: http://www.scienceofcooking.com/caramelization.htm
ABOUT MAILLAIRD REACTION TEMPERATURES
285°F (140°C) -- Browning or the Maillard Reaction begins
NOTES: Browning, or the Maillard reaction, creates flavor and changes the color of food. Maillard reactions generally only begin to occur above 285°F (140°C). Until the Maillard reaction occurs meat will have less flavor. Shown above are two identical dishes cooked (left) below (140°C) and right at much higher temperatures. Both caramelization and the maillard reaction only occur on the right producing the noticeable brown color.
HEALTH AND SAFETY TEMPERATURES
160°F/70°C -- Temperature needed to kill E.coli and Salmonella.
NOTES -- TIME AND TEMPERATURE EFFECTS
While Salmonella is killed instantly at temperatures above 160F keeping the temperature for longer periods of time at lower temperatures will also be effective. See the chart below.
for given temperature, fat level, and species needed to obtain 7-log10
lethality of Salmonella*
Times for given temperature, fat level, and species needed to obtain 7-log10 lethality of Salmonella*
-------------------------------- fat%=12 ------------------------------------
DIFFERENCE BETWEEN POACHING, SIMMERING AND BOILING
The main difference between poaching, simmering and boiling is the temperature. However food cooks differently at each of these temperatures.
160 degrees to 180 degrees F
Poaching calls for food to be fully submerged in a liquid (generally a flavorful stock) that is kept at a constant and moderate temperature, between 160° and 180°F. Eggs and fish are suitable for poaching.
185 degrees to 200 degrees F
Simmering is best used for tougher cuts of meats or foods that need more time to cook. In a simmer small bubbles rise to the surface - the gentler and slower the bubbles, the lower the temperature.
212 degrees F
Pasta is best cooked in boiling water.
For more data see: Complete Time Temperature Tables
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