Chemical loosening agent-sodium bicarbonate, ammonium bicarbonate, etc.
Biological loosening agents-fresh yeast, dry yeast and active quick-drying yeast.
Chemical loosening agents are mainly suitable for tough biscuits and crispy biscuits. Biological loosening agent is only used for fermented carding biscuits and semi-fermented biscuits.
The kind and swelling power of swelling agent have great influence on the swelling quality of biscuits. Chemical loosening agents can be divided into alkaline loosening agents and acidic loosening agents, but acidic loosening agents cannot be used alone.
1. chemical loosening agent
(1) sodium bicarbonate
Also known as sodium bicarbonate or soda, commonly known as edible baking soda. This product is white powder, odorless and salty. It decomposes rapidly above 65℃, loses all carbon dioxide when heated to 270℃, and strongly produces carbon dioxide when it meets acid.
Usage: Using the decomposition characteristics of sodium bicarbonate in biscuit production, after it is mixed into biscuit dough, a large amount of carbon dioxide will be released during baking, which will make biscuit products form porous loose bodies and taste crisp and delicious. However, due to the strong alkalinity of sodium bicarbonate, if the content is too high, the internal color of biscuits will turn yellow, which will affect the taste. If sodium bicarbonate is used, adding acid loosening agent (acid salt) can neutralize sodium carbonate and further decompose it to produce carbon dioxide, thus reducing alkalinity, loosening products and improving taste.
(2) Ammonium bicarbonate, also known as ammonium bicarbonate, stinky powder, commonly known as ammonia water. This product is a white powder crystal, which is unstable to heat and can be decomposed into ammonia, carbon dioxide and water above 35℃.
Usage: The use of ammonium bicarbonate and sodium bicarbonate in biscuit production is beneficial to control the looseness and will not leave too much alkali residue in biscuits.
In the production process, the gas produced by thermal decomposition of chemical loosening agent is the main source of biscuit expansion force. After the biscuit embryo enters the oven, NH4HCO3 firstly decomposes to produce CO2 and NH3, and then NaHCO3 also decomposes to produce CO2 as the temperature of biscuit embryo continues to rise. The decomposed gas makes the biscuit embryo expand in volume and increase in thickness sharply. Ammonium bicarbonate decomposes as soon as it enters the oven, and its expansion is 2-3 times larger than that of sodium bicarbonate. If it is added too much, the biscuits will be too crisp or scattered in all directions, which will affect the shape of the finished product or cause the biscuits to break, so the dosage should not be too much.
The total dosage of sodium bicarbonate and ammonium bicarbonate is about 0.5%- 1.2% of wheat flour. Because of the different properties of raw materials, the varieties, shapes and sizes of biscuits, and the different operation techniques, the proportion and dosage between them are also different.
With the development of new biscuit technology, in addition to the traditional sodium bicarbonate and ammonium bicarbonate, other biscuit leavening agents such as glucose δ lactone were added to improve the looseness of products and fully decompose sodium bicarbonate during baking. Some biscuit factories use sodium pyrophosphate instead of glucose δ lactone, which makes the gas release slow during baking and increases the long-term effect of gas production.
2. Biological loosening agent
(1) fresh yeast
It is obtained by centrifugal separation and squeezing of yeast liquid after yeast species are expanded, nourished and propagated, and most of the water is removed, commonly known as pressed yeast.
(2) dry yeast
A yeast obtained by drying fresh yeast at low temperature has the advantages of easy transportation and storage, but its fermentation ability is weakened, so it is very inconvenient to activate culture when it is used.
(3) Fast active dry yeast
Adding an active catalyst on the basis of dry yeast can enhance the fermentation ability, and it is very convenient to revive and cultivate when used, which can improve the fermentation rate and can be stored at room temperature for about one year. It is an ideal loosening agent for making biscuits and has been successfully developed in recent years. Yeast in fermented biscuit dough produces carbon dioxide and other substances due to respiration and fermentation.
During the baking process, the carbon dioxide gas in the fermented dough is heated and expanded together with the carbon dioxide gas decomposed by the chemical loosening agent, so that a porous structure is formed in the raw biscuit, and the finished product is crisp. At the same time, alcohol and acid will be produced in the process of yeast fermentation, and some alcohol and acid will produce aromatic esters when baking at high temperature, which will make the raw biscuits not only have proper sour taste, but also have the unique aroma of fermented products. Protein decomposition of flour and yeast during biscuit fermentation makes it easier to be absorbed by human body. In addition, yeast itself is rich in protein, and there are many vitamins, especially B vitamins, which increase with yeast fermentation and reproduction, increasing the nutritional value of biscuits.
In the traditional biscuit production process, yeast is only used as a loosening agent to comb biscuits. Today, the newly developed semi-fermentation mixing process is to make cookies by using the characteristics of the above chemical loosening agents and biological loosening agents. In the first round, the dough was fermented by yeast, and in the second round, the chemical loosening agent was used, which greatly improved the quality of biscuits, and was more advanced than the single traditional method in terms of taste, commodity, product specifications, crushing rate and operation stability.