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The nutritional value of ice cream is very high, the fat content is 6% to 12% (some varieties can reach 16% or more), the protein content is 3% to 4%, the sucrose content is 14% to 18% (the sugar content of fruit ice cream Up to 27%), and contains vitamins A, B, D, etc., the calorific value up to 8 joules / gram. Therefore, ice cream is a kind of nutrient-rich cold food.
There are many varieties of ice cream, which are classified according to composition: high-class creamy ice cream, fat content 14% to 16%, total dry matter content 38% to 42%, creamy ice cream, fat at 10% to 12%, total dry matter at 34 % ~ 38%; milk ice cream, fat in 5% ~ 8%, total dry matter in 32% ~ 34%. Each of the above ice creams can be divided into cream, vanilla, various fruits, eggs, and sandwiches. According to the raw materials and accessories used, it can be divided into spices, fruits, nuts, glutinous rice, pudding, sour and coated chocolate ice cream. In addition, it can be classified according to shape, such as egg rolls, brick ice cream, and the like.
(1) The ingredients of the selected ice cream for making ice cream ingredients can be prepared by the following raw materials, and the composition and properties of various raw materials are well grasped. According to the product quality standards, the quantity and ratio of the raw materials are calculated and used rationally.
1. Sources of ingredients for ice cream (1) Fats can be prepared from cream, butter, margarine, refined vegetable oils, and the like.
(2) Non-fat solids can be prepared from raw milk, skimmed milk, condensed milk, milk powder, and the like.
(3) Sugar can use sucrose, fructose syrup, glucose and the like.
(4) Emulsifiers and stabilizers Eggs, egg yolk powder, gelatin, agar, sodium alginate, carboxymethyl cellulose, and the like can be used.
(5) Spices include vanillin, cocoa, nuts, and various fruit flavors.
2. Performance of Various Raw Ingredients in Milk (1) Milk and Dairy Products Milk and dairy products are the main raw materials for making ice cream. They provide fat and non-fat solids to ice cream, giving the ice cream good flavor, soft and delicate taste and Rich in nutritional value. The amount and quality of fat in ice cream has a great relationship with the quality of the finished product. If the fat content is small, the taste of the ice cream is not fat. The milk fat in the ice cream mix needs to be homogenized, so that the emulsification effect can be increased, the viscosity of the feed liquid can be increased, and it is also favorable for increasing the expansion ratio during freezing and stirring. Therefore, the fat used for ice cream is preferably fresh, salt-free cream or cream, and its acidity does not exceed 17 degrees (T), and the fat content is more than 30%. In addition, partially hydrogenated oils can also be used.
Non-fat milk solids in ice cream can be formulated with raw milk and condensed milk. Condensed milk has a special aroma that can enhance the flavor of the product and is often mixed with raw milk. Milk powder can also be used for the formulation of non-fat milk solids, but if all milk powder is used, the tissue state and expansion rate of the ice cream product can be affected. It is necessary to control the use of poor quality, such as the use of excessively high acidity, otherwise the mixed ingredients will agglomerate during heating and sterilizing, and the ice cream products will produce sourness. In addition, the non-fat milk solids can not be too high or too low, and the general content is preferably 8% to 10%. When the content is too high, it will affect the flavor of milk fat and produce a slight salty taste. After a long time of storage, there will be defects of grit-like tissue structure. When the content is too small, the structure of the product will be loose, and it will shrink easily, and the shape will lack stability. Therefore, it is necessary to reasonably control the content of non-fat milk solids in the mixed ingredients.
(2) Sweeteners The sweeteners in ice cream products not only give the products a sweet taste, but also make the ice cream products delicate in texture and reduce the freezing point during freezing. Sweeteners can be sucrose, starch syrup, glucose and the like. The amount of sucrose is generally 12% to 16%. If it is less than 12%, the sweetness of the product is insufficient; the content of sugar is too high, the expansion rate during freezing is low, and the product lacks a refreshing feeling.
(3) Eggs and egg products Because eggs and egg products contain lecithin with emulsifying and stabilizing agents, the use of egg or egg yolk powder products in ice cream can improve the state and flavor of the tissues, giving the ice cream tissue a delicate texture and structure. Stable form, and can increase the nutritional value of the product. The amount of egg product (4% for eggs and 0.5% to 2.5% for egg yolk powder) will make the ice cream have the aroma of the milk cake, and if there is an excess, there will be an egg smell.
(4) Stabilizers are also called modifiers. The purpose of using stabilizers is to use the strong absorbent property of stabilizers to increase the viscosity and expansion rate of ice cream, prevent the formation of ice crystals, reduce the roughness, and make the ice cream tissue delicate and smooth. Not easy to melt, while improving ice cream shape retention and hardness. Stabilizers are usually the general name for binders and fillers. Its main function is to ensure the body and texture of ice cream, not to replace the non-fat milk solids. There are two types of stabilizers commonly used, one is pectin, gelatin, and sodium caseinate proteins; the other is carbonization and other substances such as sodium alginate, agar, and carboxymethyl cellulose. Among these stabilizers, gelatin is a good stabilizer, and it absorbs 14 times as much water as it expands in warm water, but loses its ability to swell in hot water above 70°C. The agar has a strong gel and water absorption, and the absorbed water is 17 times that of itself. However, the gel formation ability will decrease in acidic solution. Therefore, pay attention to the amount of stabilizer used and the conditions of use when mixing ingredients. The amount of stabilizer is 0.2% to 0.4%.
(5) Perfumes and Colorants There are many types of flavors and colors, including natural extracts and chemically synthesized products. The most used spices are vanillin, strawberries, chocolate, coffee, various juices, etc. The addition of pigments makes the appearance of ice cream brighter and increases appetite. However, the use of pigments must match the name and aroma of the ice cream. Such as lemon ice cream should add lemon yellow.
(b) ice cream manufacturing process ice cream manufacturing process can be divided into the front and back two processes, in the former part is mainly ingredients, homogenization, sterilization, cooling and maturation. The latter part is mainly freeze coagulation, molding and hardening. Its processing process is as follows:
Mixing of raw materials → filtration → homogenization → sterilization → cooling → adding spices → maturation → freezing → filling → hardening → packaging → storage
1. Modulation of the mixed base After the various raw materials are calculated according to the recipe, they are mixed in order according to the processing technology requirements. Firstly, the raw materials with low viscosity are added into batching cylinders with sterilization, stirring and cooling functions, such as milk, skim milk, condensed milk and the like. Then add solid ingredients such as sugar, milk powder, and emulsifier to the other container and stir with water. Dissolve it completely. After filtering, pour it into a mixing bowl and mix it with milk. The batch temperature at this time is about 50°C. In addition, sugar, etc. can also be made into 65% to 70% of the syrup for use. Cream or hydrogenated oil can be heated first and used after melting. Stabilizers such as gelatin should first be made into a 10% solution with water and then added to a mixture solution of about 50°C.
After all ingredients are added, stir well. The acidity of the mixture should be 0.18% to 0.2%, not more than 0.25%, or solidification will occur during sterilization. When the acidity is too high, it can be neutralized with baking soda or alkali, but excessive neutralization will have astringency. The spices are preferably added after the mixture is sterilized, homogenized, cooled, or frozen.
2. Sterilization of the bactericidal mixture can be carried out at 75 to 78°C for 15 minutes. Without affecting the quality of ice cream, 75-76°C and 20-30 minutes of sterilization are also available. Sterilization should achieve the purpose of killing pathogens, bacteria, molds and yeasts to ensure that the number of bacteria in the mixture is less than 50 per milliliter.
3. Homogeneity In order to make the ice cream products delicate and lubricate, the shape is stable and long-lasting, the expansion rate is increased, and the ice crystallization is reduced, it is necessary to homogenize the mixture liquid. The temperature should not be too low or too high during homogenization. Low temperature increases the viscosity of the feed solution, resulting in poor homogenization and prolonged mixing time during freezing. If the material is homogenized under a temperature of more than 80°C, fat accumulation is promoted and the expansion rate is also lowered. Homogeneous pressure also has a certain range. If the pressure is too low, the homogenization effect cannot be achieved. If the pressure is too high, the stiffness of the feed liquid will increase, and the air will not be mixed easily during freezing and stirring. Generally, the homogenization is carried out at a temperature of 63 to 65° C. after sterilization, and 150 to 180 kg/cm 3 of pressure.
4. The purpose of mature and mature is to make the protein, fat condensate, stabilizer and other materials fully water and swell, increase the viscosity, make the foaming of the mixture good, and help to increase the expansion rate during freezing and shorten the freezing time. Mature needs to store the material at 4 ~ 5 °C for 8 to 24 hours. The container should be covered with dust when it is mature to prevent the entry of bacteria and odors. In recent years, due to the improvement of the performance of emulsifiers and stabilizers, the maturation time has been greatly shortened, and generally it takes only 3 to 5 hours to complete maturation.
5. Freezing and freezing is the mixing of the mature mixed base material through the ice cream machine (Figure 4-5), mixing with air and freezing, so that the product is solidified into a semi-solid state, and the ice cream is obtained which has fine texture, good body, and high expansion rate. product. Therefore, freezing is an important process of ice cream production. Production should pay attention to two links:
(1) Mixing amount of air During the freezing process, a certain amount of air is pressed in while being stirred intensively so that air and tiny air bubbles are uniformly distributed in the entire mixture, which not only increases the volume of the ice cream but also improves the organization of the product. status. Ice cream without air is mixed and its products are hard without taste. If the air is mixed in too much, the volume of the ice cream will increase, but the texture and texture of the product will become poor. The phenomenon of increasing the volume of ice cream by freezing and stirring the mixed base and mixing it into the air is called a compatibilization. The size of the ice cream's capacity expansion is expressed by the expansion rate:
Expansion ratio (%) = (volume of ice cream - volume of mixture) / volume of mixture 100
The suitable ice cream cream has a swelling rate of 90% to 100%, and the fruity ice cream is 60% to 70%. The general swelling rate is preferably 2 to 2.5 times the dry matter of the mixed raw materials. The expansion rate is also affected by the content of the raw materials. When the fat is below 10%, the swelling rate of the product increases with the increase of fat content. The expansion rate of the ice cream is 8% to 10% when the fat-free solid material is used. The sugar content is suitable at 13% to 14%. Too much stabilizer such as gelatin will increase the viscosity and reduce the expansion rate.
(2) Freezing temperature The organization of ice cream is related to the size of the ice crystals contained. Only the rapid freezing will cause the ice crystals to become fine. The continuous ice cream machine allows the moisture in the mixture to form a 5 to 10 micron crystal, making the product smooth and free from graininess. This requires the ice cream machine outlet temperature should be -6 ~ -3 °C is appropriate. The formation of fine ice crystals is also related to the agitation strength, the temperature and viscosity of the mixed base itself. The temperature of the mixture fed into the ice cream machine after ripening should be preferably 2 to 3°C.
If the freezing time is too short during freezing, this is mainly due to the freezing temperature of the ice cream machine or the temperature of the mixing base being too low. This will cause the amount of air mixed in the ice cream to be too small, the air bubbles to be uneven, and the product structure to be hard, heavy and unconformable. Conversely, if the freezing time is too long, it is caused by the freezing temperature of the ice cream machine and the temperature of the mixture being too high, and the non-fat solid content is too high. As a result, the mixed air bubbles disappear, milk fat is condensed into small particles, and the product is poor in texture and poor in mouthfeel.
6. After the hardened and frozen ice cream is filled and packaged, it must be subjected to a low-temperature freezing process for a certain period of time to fix the state of the ice cream and make the water in the product form a very fine ice crystal, so as to maintain a certain degree of softness and hardness of the product. The process is called hardening of ice cream. The ice cream leaving the ice cream machine should quickly harden, otherwise any warming will cause the small ice crystals to melt and agglomerate. After hardening, larger ice crystal particles will form, and the tiny air chamber will be destroyed and cause shrinkage. The finished product will be rough and the quality will be reduced. The hardening time is affected by the size of the container, the degree of expansion, and the temperature of the freezing temperature. The hardening temperature is usually required to be -25 to -18°C and the time is 12 to 24 hours.
Ice cream manufacturing
Ice cream is made of milk or dairy products and sucrose as the main raw material, and is added with raw materials such as eggs or egg products, emulsifiers, stabilizers, and spices. It is made by mixing, sterilizing, homogenizing, maturing, freezing, forming, and hardening. The soft and delicious frozen food.