Text 9. Freezing

There are several different freezing methods available to meat processors. Recent advances in the design of fast freezers are proving to be very advantageous for companies involved in the production of frozen meat products that come in small sizes, such as bacon bits or ground meat.

Individual quick freezing, shortened to IQF, is a process usually applied to "naked" products such as dices, strips of meat, sausages, ham and also ground meat, which can be in raw, cooked or fried form.

Using the individual quick freezing process, the separa­tion of the different pieces of dices, strips or ground meat is maintained during the freez­ing process, without the for­mation of blocks or lumps. When the products are used in further processing, they are more convenient to handle for both the consumer as well as for the industry.

Convenience and quality. One negative aspect of slow freezing is the fact that it cre­ates large ice crystals in frozen products. If the freezing time is long (meaning hours), the ice crystals can be so big that they destroy the cells that make up the products. This can be noted as extensive liq­uid drip loss when the prod­uct is thawed.

Quick freezing eliminates these disadvantages. Both the frozen and thawed products retain their natural textures and colours and the water loss is negligible when thawed.

Extremely quick freezing of meat products can be achieved in industrial produc­tion through, for example, cryogenic freezers, IQF freez­ers or impingement freezers. When used for hamburgers, the freezing time is lowered to a few minutes and dehydra­tion losses during the freezing process are negligible. Dehydration losses are other­wise significant if the product is frozen in an overnight cold storage.

The market for quickly frozen products. The market for food products frozen using the individual quick freezing technique is steadily increasing. Among the driving forces behind this trend are convenience, quali­ty, and economy. Furthermore, demographic changes, such as the increas­ing number of one-person households, are also feeding demand, since products in which individual quick freez­ing has been applied are used to create dinners with individ­ually frozen ingredients.

The catering and the ready-meal industry use a lot of IQF products as ingredients and thus are big consumers. Sticky products have to be frozen so that they can pass through portioning machines and all products benefit from being frozen when portioned.

Slow freezing creates such large ice crystals in frozen products that they destroy the cells that make up the products. This can be noted as extensive liquid drip loss when the product is thawed. Quick freezing eliminates these disadvantages. Both the frozen and thawed products retain their natural textures and colours and the water loss is negligible when thawed.

The fluidised bed freezer. The year 2000 saw the launch of a new concept in individual quick freezing based on a patent for the transportation of products in a semi-fluidised bed, which allowed the design of a com­pact freezer that fulfilled the production needs of the meat industry. To date, this new freezer has provided an excel­lent hygienic design, high per­formance figures and low operational costs. These char­acteristics represent clear improvements compared to traditional IQF freezers.

The company IQF Frost decided to test a proto­type of the quick freezer in their line. The installation was easy and the prototype had surprisingly few 'children's diseases'. Among the features of the fluidised bed freezer is the possibility to freeze cooked or fried products straight from the oven or fryer down to -20°C in a couple of minutes. And because it uses the indi­vidual quick freezing process, the degree of separation of the products is excellent and the appearance and texture of the thawed product is natural.

UNIT III. POWER ENGINEERING

TEXT 1. Electric Circuit

This is a circuit. Its elements are a voltage source, a resistor and a conductor. The circuit consists of a voltage source, a resistor and a conductor. A voltage source supplies current. A resistor reduces current. A conductor connects the elements of the circuit

Compare circuit a with circuit b. What is the difference between them? Current passes through circuit a while no current passes through circuit b. Circuit b has an open. No cur­rent through circuit b results from an open. An open and a short are troubles in a circuit. A trouble in a circuit may result in no current in it.

TEXT 2. Series Circuit and Parallel Circuit

Compare circuits a and b. Circuit a consists of a voltage source and two resistors. The resistors are connected in series. Circuit a is a series circuit.

Circuit b consists of a voltage source and two resistors. The resistors are connected in parallel. Circuit b is a parallel circuit.

A parallel circuit has the main line and parallel branches.

In circuit b the value of voltage in R1 equals the value of voltage in R2. The value of voltage is the same in all the ele­ments of a parallel circuit while the value of current is different. A parallel circuit is used in order to have the same value of voltage.

In circuit a the value of current in R1 equals the value of current in R2. The value of current is the same in all the ele­ments of a series circuit while the value of voltage is different. A series circuit is used in order to have the same value of current. In R1, V1=IR1 is the voltage drop in R1. In circuit c a trouble in one element results in no current in the whole circuit. In circuit d a trouble in one branch results in no current in that branch only, a trouble in the main line results in no cur­rent in the whole circuit.

TEXT 3. Capacitors

A capacitor is one of the main elements of a circuit It is used to store electric energy. A capacitor stores electric energy provided mat a voltage source is applied to it.

Fig.8 Fig.9

The main parts of a capacitor are metal plates and insulators. The function of insulators is to isolate the metal plates and in this way to prevent a short

In the diagram one can see two common types of capacitors in use nowadays: a fixed capacitor and a variable one. The plates of a fixed capacitor cannot be moved; for this reason its capacity does not change. The plates of a variable capacitor move; its capacity changes. The greater the distance between the plates, the less is the capacity of a ca­pacitor. Variable capacitors are commonly used by radiomen; their function is to vary the frequency in the circuit. Fixed capacitors are used in telephone and radio work.

Fixed capacitors have insulators produced of paper, ceramics and other materials; variable capacitors have air insulators. Paper capacitors are commonly used in radio and electronics; their advantage is their high capacity: it may be higher than 1,000 picofarad.

Besides, electrolyte capacitors are highly in use. They also have a very high capacity: it varies from 0.S to 2,000 microfarad. Their disadvantage is that they change their capacity when the temperature changes. They can operate without a change only at temperatures not lower than -40 degrees C.

Common troubles in capacitors are an open and a short. A capacitor stops operating and does not store energy in case it has a trouble. A capacitor with a trouble should be substituted by a new one.