Baking, also known as baking and baking, refers to the drying and hardening of materials by dry heat under the burning point of materials.
Baking is an indispensable step in the production of bread and cake products. After a series of chemical changes, such as gelatinization of starch and denaturation of protein, bread and cake can reach the goal of ripening. It can also change the taste of food.
Bread baking generally includes the following three stages:
1) The first stage: surface fire 120 – 160 ℃, primer 180 – 220 ℃; after the actual temperature reaches the set temperature, bread is put into the furnace. The maintenance time is about 2-15 minutes.
Note: the temperature of small bread is high and the time is short; the temperature of big bread is low and the time is long;
Function: bread to increase the volume, mainly to let it grow high.
2) The second stage: raise the surface fire to 180 – 220 ℃, the primer 200 – 250 ℃, and maintain it for about 5-10 minutes when the surface fire meets the requirements.
Function: make the bread form a hard crust and shape the bread.
3) The third stage: maintain the noodle fire at 180-220 ℃ and lower the primer to 180 ℃ until the bread is evenly colored, which takes about 5-10 minutes.
Function: make the bread form uniform brown or golden yellow.
Changes in the interior of bread during baking
Change of temperature and moisture content and formation of internal structure of bread.
After the bread is in the oven, the sources or ways of receiving heat at the same time are: heat radiation of heating tube, heat conduction of baking plate, convection heat transfer of hot air in the oven.
A. Early baking
a) The formation of epidermis
The surface temperature of the green billet, which has just been put into the furnace, is about 30 ℃. The moisture in the hot air will be condensed into water droplets by the cold billet and attached to its surface. But this happens in a very short period of time, and soon the water droplets will vaporize, and the surface temperature of bread will rise rapidly to above 100 ℃, so that the surface will dry and form a thin white skin.
b) Formation of bread crust
At the same time, the heat is transferred to the interior, and the temperature of the inner layer is also rising. In a short time, the temperature under the epidermis is is close to 100 ℃, forming a temperature gradient distribution of high outside and low inside. In this way, the heat transfer direction (driving force) is from the outside to the inside.
However, the moisture distribution in bread is just the opposite, which is the gradient distribution of low outside and high inside. In this way, the water is replenished from the inside out, and an evaporation layer is formed under the epidermis (because the temperature is close to 100 ℃).
However, during the baking process, the internal temperature will continue to rise. When the gelatinization temperature of starch is reached (higher than 50 ℃), the water will be combined with starch, so that the internal supplement of water will be less and less, the evaporation layer moisture will be reduced, and the temperature will be more than 100 ℃. Then, the outer crust of bread will be dried into a layer of anhydrous bread shell (the product is called bread skin after absorbing moisture and softening)
B. Late baking
a) Formation of bread sacs
As the baking continues, the heat continues to pass in. Due to the blocking effect of the crust and the internal gelatinization, the amount of water diffused outward is limited, but the temperature will continue to rise, and eventually close to 100 ℃, so the protein will also denatured. After starch gelatinization and protein denaturation, the lower part of the bread shell forms a bread bag, which is actually ripening.
b) Formation of bread sacs
The geometric center of bread gets the least heat and slowest heating rate in the baking process. Because of the big difference between the central temperature and the temperature of the crust, the moisture in the middle part of the bread bag not only diffuses outward, but also seeps and condenses inward. When the bread bag is formed, the moisture content in the center of bread is 2% higher than before, and the temperature will eventually rise to 90-98 ℃. And form the core of bread sac.
Changes in volume and weight of bread during bakin
The reasons for the increase in volume are as follows:
a. Expansion gas source: CO2, water, alcohol, acid, aldehyde heat expansion;
b. Starch gelatinized and expanded;
c. After denaturation, the protein becomes rigid and maintains its expanded volume structure.
a. Pre fermentation conditions: including yeast activity, dough gas holding capacity and refreshing state;
b. Initial baking temperature: suitable. When it is too high, the bread will form quickly, which is not conducive to the expansion of the later volume;
c. Baking humidity: wet the skin with hot and humid air, otherwise it will crack;
d. Whether to use baking mould or not: the mould reduces the effective area of the air emitted from the bread.
Weight change after baking
Generally, the weight will be lost by 10-12% after baking. The main materials and proportion of losses are as follows:
The water content was 95%, ethanol 1.5%, co23.3%, volatile acid 0.3%, acetaldehyde 0.08%. The weight loss is mainly related to the size of the machine package and whether the baking mold is used.
Many novice bakers are not sure about the time and oven temperature when making cakes, which leads to the hard-working cakes not cooked or well cooked. I believe that no one wants to encounter this situation. So today I'm going to talk to novices about how to master baking time and temperature
1. Types of cakes
The higher the sugar content of the cake, the lower the baking temperature, which can make the cake baking normal and not easy to produce Caramel effect;
2. The size of the cake
The bigger the cake is, the lower the baking temperature is, so that the central position of the cake can be fully cooked and the bottom and surrounding areas will not be burnt;
3. The quality of the cake
The higher the sugar content of the cake, the lower the baking temperature, which can make the cake baking normal and not easy to produce Caramel effect；
4. Thickness and density of cake
Cake with high density, such as oil cake, should be baked at low temperature. It takes a long time to bake the oil cake because of its fine texture. Sponge cake doesn't need to be baked for a long time because of its loose tissue. Therefore, the temperature can be adjusted to maintain its temperature and texture；
5. Oven load
When the load of the oven reaches its peak, its temperature will drop the fastest. The temperature of the oven can be adjusted up to 5 ~ 10 ℃, but when the load is small, the temperature can be reduced. At this time, the temperature should be reduced by 5 ~ 10 ℃