Page 6 - The Chemistry of Cooking
P. 6
The Process of Deep Frying
• 1. Initial heating. In the first stage, 2. Surface boiling. In this stage, 3. Decreasing heat 4. Bubble end point. This is the
the food is completely submerged into we see tiny exploding bubbles transfer rate. As the crust last stage of deep-frying, in which
the hot oil, until the surface of the sizzling at the surface of the food. continues to dehydrate, it very few bubbles appear on the
food reaches the boiling point of conducts less heat to the rest surface of the fried food. At this
water. This stage lasts for about 10 Contrary to popular belief, this
seconds [1]. At this point, the heat doesn’t mean that the oil is boiling. of the food, so the rate of stage, water from inside the food is
from the oil is transferred to the food’s Instead, the hot oil surrounding heat transfer through no longer evaporating, either
surface by diffusion and also the food causes water inside the escaping steam to decreases because all the water from inside the
by convection – a process which moves (reduced bubbling) [1]. The food is gone, or heat transfer from
heat due to the bulk circulation of the food to evaporate, so the little
oil’s currents from a warmer region to bubbles surface as bursts of steam remaining moisture inside of the crust to the core has reduced to
the cooler region surrounding the escaping to the food’s exterior the food is slowly heated to the point where it becomes
food. While convection uniformly (think jacuzzi steam jets). The the boiling point of water, improbable that the water will
heats the food’s surface, it doesn’t cook which cooks the food inside evaporate [1]. At this point, the fried
the center of the food. Rather, the movement caused by the bubbling
food’s center is heated circulates the currents of the as if it were boiled, product should to be removed from
through conduction, the process by frying oil, which increases the rate gelatinizing the starch and the oil, or else the oil will begin to
which heat diffuses from the food’s hot of heat transfer by “forced denaturing the proteins in the seep into the fried product and make
surface into its core through the food . Now, most of the it soggy, since there are no more
physical contact of molecules and convection” and cooks the food
transfer of their thermal energy. faster moisture from the food is water vapor bubbles to counteract
lost. the diffusion of oil inwards.
