Ice-cream and other frozen products manufacturing equipment may be classified as batch freezers, hand operated, kulfi maker, direct expansion type batch freezers and continuous freezers, etc.
i. Hand Operated Unit
It is shown in figure-3.5, has a wooden cylindrical case to accommodate broken ice+salt, a mix can and dasher assembly. The mix-can is made of either aluminum or mild steel with tin coating. This is designed such that it is pivoted in the bottom and has a geared drive system. The dasher remains stationary to facilitate scraper of frozen mass and keep mix moving for better freezing efficiency. This unit is commonly used at domestic level.
ii. Kulfi Maker
Little larger scale operation is through a kulfi maker. In this traditional method, the prepared mix is filled in the metal containers usually cone/square shaped. The size of containers is such that the quantity is served once. These containers are placed in a clay pot or a metallic container, which is large enough to accommodate the broken ice. Salt is added to lower the freezing point, thus causing faster freezing.This type of kulfi maker is very common at entrepreneur level. Care is taken to seal the container to the extent that the brine water does not leak through in the product.
iii. Direct Expansion Type Freezer
The batch freezers are the most common units shown in figure.3.6 and 3.7. These are cylindrical in shape with one jacket for refrigerant and the other for insulation.The cylinder acts as an evaporator of a refrigeration system. It is made of stainless steel.Normally, this is of 6 kg and 12 kg mix holding capacity. After freezing, the volume of mix gets doubled as the air gets incorporated. The mix is agitated by the dasher. The dasher does two jobs, firstly to remove frozen mix from the inner shell and second to agitate the mix such that the mix does not freeze into one solid mass.During agitation a filtered atmospheric or pressurized air is sent into the mix. The air gets trapped causing overrun of frozen mass. This increase in volume is called overrun.
Continuous type freezer: As the scale of production increases over 500kg/h, the continuous or instant freezers are used. The mix is continuously pumped into the freezer cylinder and the frozen mass is discharged from the machine.The principle of freezing is the same, however improved automation and control are necessary. The desired amount of overrun and degree of freezing can be adjusted with these controls. Pumping of mix is half the volume of the ice-cream outlet pump. Similarly, the dasher design is such that the mix flows from one end to outlet without backward flow.
In both the freezers, the frozen mix coming out is in flowable state. It is soft at –10 o Cand served as softy. The frozen product is filled into cups/bricks and put into hardening freezers for hardening and is served to consumers as ice cream. Soft serve freezers or softy plants are like batch freezers where soft frozen mix is directly drawn into edible cones or cups. Once the mix is frozen, the dashers keep rotating and the refrigerant is switched off. This way, the mix keeps in a flowable state and the temperature is between –5 o to –10 o C, no hardening is required.
i. Hand Operated Unit
It is shown in figure-3.5, has a wooden cylindrical case to accommodate broken ice+salt, a mix can and dasher assembly. The mix-can is made of either aluminum or mild steel with tin coating. This is designed such that it is pivoted in the bottom and has a geared drive system. The dasher remains stationary to facilitate scraper of frozen mass and keep mix moving for better freezing efficiency. This unit is commonly used at domestic level.
ii. Kulfi Maker
Little larger scale operation is through a kulfi maker. In this traditional method, the prepared mix is filled in the metal containers usually cone/square shaped. The size of containers is such that the quantity is served once. These containers are placed in a clay pot or a metallic container, which is large enough to accommodate the broken ice. Salt is added to lower the freezing point, thus causing faster freezing.This type of kulfi maker is very common at entrepreneur level. Care is taken to seal the container to the extent that the brine water does not leak through in the product.
iii. Direct Expansion Type Freezer
The batch freezers are the most common units shown in figure.3.6 and 3.7. These are cylindrical in shape with one jacket for refrigerant and the other for insulation.The cylinder acts as an evaporator of a refrigeration system. It is made of stainless steel.Normally, this is of 6 kg and 12 kg mix holding capacity. After freezing, the volume of mix gets doubled as the air gets incorporated. The mix is agitated by the dasher. The dasher does two jobs, firstly to remove frozen mix from the inner shell and second to agitate the mix such that the mix does not freeze into one solid mass.During agitation a filtered atmospheric or pressurized air is sent into the mix. The air gets trapped causing overrun of frozen mass. This increase in volume is called overrun.
Continuous type freezer: As the scale of production increases over 500kg/h, the continuous or instant freezers are used. The mix is continuously pumped into the freezer cylinder and the frozen mass is discharged from the machine.The principle of freezing is the same, however improved automation and control are necessary. The desired amount of overrun and degree of freezing can be adjusted with these controls. Pumping of mix is half the volume of the ice-cream outlet pump. Similarly, the dasher design is such that the mix flows from one end to outlet without backward flow.
In both the freezers, the frozen mix coming out is in flowable state. It is soft at –10 o Cand served as softy. The frozen product is filled into cups/bricks and put into hardening freezers for hardening and is served to consumers as ice cream. Soft serve freezers or softy plants are like batch freezers where soft frozen mix is directly drawn into edible cones or cups. Once the mix is frozen, the dashers keep rotating and the refrigerant is switched off. This way, the mix keeps in a flowable state and the temperature is between –5 o to –10 o C, no hardening is required.
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