Fried is edible oils for heat transfer media. The heat capacity for oil 2 J (℃ · g), warming faster, good fluidity, the oil temperature is high. Fried heat transfer is mainly by when conduction modes, followed by convection. Heat transfer to the first heat Fried container, oil absorbs heat from the tank surface again to the surface of food, then part of the heat in the food directly by the oil into, make food internal components and mature, dehydrated rapidly heated. Fried created during the decomposition objects can be divided into two kinds, one kind is volatile decomposition products, another kind is the volatile decomposition products.
Fried products processing, food in some of the temperature will be the hot oil, the oil can provide fast and uniform heat, food surface temperature rapid ascension, water gasification, the surface appears a layer of dry layer, form scale. Then, water vaporizing layer to food and internal migration, when food surface temperature rise to the temperature of the hot oil, the temperature inside the food slowly incline to 100 ℃, and surface focal saccharification reaction happened and protein denaturation, other material decomposition, produce distinctive smell of Fried. Fried the rate of infection depends on the oil temperature and the temperature difference between internal food and food coefficient of thermal conductivity. In Fried hot system process, dry food surface layer porous structure has its characteristic of gap vary in size. Fried process water and steam from these big gaps in first separation, and then replaced by hot oil vapour of possession space, move out of the water by the oil film, oil film interface layer thickness control of the heat transfer and the qualitative, its thickness and oil viscosity and flow speed related, and drying similar, dehydration is the driving force of the water vapor pressure inside food only poor. Because when Fried food surface hardening film, make its food internal water vapor evaporation suffocate suffocate, forming a certain steam pressure, water vapor through enhanced, the food fast cure, therefore Fried products with golden in color, in the Lebanon, dry crisp taste sweet characteristic.
In Fried process, oil and food of heat transfer between quality and change is a dynamic balance of the process.
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