Ice cream, as a frozen dairy product, its physical and chemical systems are fairly complex. In which, air bubbles dispersed in the continuous ice crystals liquid, the liquid contains particles of fat, milk protein, insoluble salt, lactose crystals, plastic Body stabilizer and sucrose, lactose, soluble salts, so it is a gas, liquid and solid phase composition of three-phase system and can be regarded as air bubbles partially frozen with 40% -50%  air. To achieve the required quality standards and physical structure of ice cream, the composition (formulation and raw materials quality), the production conditions and equipment three aspects should be taken into consideration.

1: The composition (formulation and raw materials quality)

The main materials used in ice cream making are fat, non-solid fat, sweeteners, emulsifiers, stabilizers, spices and coloring.

1.1  Fat

Milk fat is typically applied in ice cream making to give the ice cream the unique aromatic flavor, tissue lubrication, better texture and original shape fixing. So generally speaking, the more milk fat put in, the better the quality of ice cream could be. Milk fat comes from pure milk fat butter, cream, milk, condensed milk, milk powder, etc. So to make ice cream with better quality, sanitary, high milk fat should be chosen. However, as milk fat is very expensive and its usage amount is limited, for save cost concern, most people in the world will use vegetable fat instead, such as margarine, hydrogenated oils, palm oil, coconut oil ect.

1.2 Non-solid fat

Non-solid fat comes from total milk solid (without fat), contains fat and protein, lactose and minerals. Among which, protein has hydration function, which could form a stable film together with emulsification on the surface of small fat globules, ensure the oil emulsion in the water, and meanwhile to ensure enough air into the ice cream in the freezing process.

Non-fat milk solids are generally made from fluid milk, condensed milk, milk powder, whey powder.

1.3 Sweeteners

Generally speaking, sweeteners refer to sucrose, 15%-16% content in ice cream making. Sweeteners, not only gives ice cream sweet flavor, but have a function of lowering the freezing point. But in order to improve ice cream texture, vary ice cream flavors and lower cost, many people sometimes add some additives to sweeteners: such as honey, saccharin, protein, sugar, stevia ect.

1.4 Stabilizers

Stabilizers is hydrophilic, which could be combined with water so as to improve the viscosity and the overrun of ice cream, prevent ice crystal, make the ice cream more smooth on organization structure. Several points should be take into consideration when choosing emulsifiers: soluble in water or ice cream mixture; could confer the mixture better viscosity and foaming; could improve the texture and structure of ice cream; shape maintenance of ice cream; preventing crystallization expansion ; cheap costs.

1.5 Emulsifiers

Emulsifier is a molecule with hydrophilic and lipophilic substances, which lies between water and oil, so that one party could be easily dispersed into the other party, form a stable emulsion, cream mixture. The structure of ice cream is fairly complex, with the add of emulsifiers, besides emulsion, the other functions could be summarized as below: better emulsion of fat globules, make it more stabilized; disperse other articles(besides fat globules), make it more stabilized; increase the heat resistance of ice cream; prevent or control the formation of ice, so ice cream has delicate organization and better texture.

1.6 Spices

With the add of spices, the ice cream will have a natural fragrance. The quality of spices will have a direct influence on ice cream, so should be a big concern when choosing.

2. The Production Conditions/ Craftsmanship of the Ice Cream

For ice cream making, one has to comply with strict production skills and principles, otherwise it can not produce good quality ice cream.

2.1 Raw Material

Raw materials directly affect the quality of ice cream quality. Therefore, all raw materials must be tested in strict accordance with quality standards, unqualified should not be used.

2.2 Raw Material Batching

The basic step for ice cream making is raw material batching, namely ice cream recipe or ice cream formulations, which is affected by several factors: consumer preferences, raw material prices and availability, product sales volume. Based on pre-determined quality standards, using mathematical methods to calculate the amount of various raw materials required in order to ensure the quality of products made in line with technical standards

2.3 Pasteurization

The method of pasteurization has an important impact on the flavor of ice cream. The usual pasteurization methods are: pasteurize the Ice cream mixture in the tank with a jacket of steam pasteurizer to 78 ℃, then keeps for 30 minutes; if use continuous pasteurization device for high temperature sterilization (HTST), to heat the mixture to 83 ~ 85 ℃, keeps for 15 seconds is enough, longer time might make ice cream have burst taste.

2.4 Homogenization

Homogenization has larger relation with the structure of ice cream. Generally two high-pressure homogenizer is commonly used for homogenizing. Homogenization could make the fat globules diameter smaller, usually ranging from 1 ~ 2μm, at the same time to increase the viscosity of the mixture and ensure that the delicate tissue of ice cream products. The most appropriate temperature for homogenization is 65 ~ 70 ℃, the first -stage homogenization pressure is15-20MP, second-stage 2-5MP, homogenization pressure will accordingly decrease with the increase solids and fat content of the ice cream.

2.5 Ageing

Aging is cool the mixture to 2 ~ 4 ℃for storage, known as the “mature” or “aging.” The essence of ageing is that fat, protein and stabilizer hydration, stabilizers fully absorb the moisture so that the liquid viscosity increases, favorably increase the overrun of ice cream when freezing.

Aging time depends on the composition of raw materials and stabilizer species, generally 4 ~ 24h. When ageing, bacterial contamination should be avoided.

2.6 Freezing

Freezing is to freeze the ice cream mixture when stirring, make the air in the tiny bubbles and then evenly distributed in the entire state of mixture, part of the water into tiny ice crystals. And its role is: (1) increased creases the viscosity of ice cream mixture, gradually thicken into a semi-solid state, that is Freezing state. (2) Because of the agitation beating, constantly scraped tiny ice cream materials from the freezing cylinder wall, to prevent the ice cream mixture into large flake ice. (3) The constant stirring and cooling, air will be into the ice cream when freezing to increase its overrun and thus to make beautiful ice cream with better organization and perfect shape. The outer temperature of the ice cream around -5~ -6℃.

2.7 Blast Freezing, Hardening & Storage

The function of blast freezing is to fast freeze the ice cream ( after comes out from the batch freezer) to -23 ℃. The function of blast freezing is to stabilize the structure of ice cream, make it into form in a very small ice crystal. Keep the ice cream in a appropriate state for sales, storage and easy transportation.

3. Machinery

Machinery is of course a big concern for making good ice cream. Based on ice cream making process, the machinery for ice cream making should be Ingredients cylinder, pasteurizer, homogenizer, aging machine, batch freezer, blast chiller, cold room ect.

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