Theme 10. Refrigeration Equipment

Task 1. Topical Vocabulary

Refrigeration is, along with the actual cooking, one of the most important parts of a kitchen. It’s something that we might often take for granted – but it hasn’t always been so easy for restaurants and foodservice operations to keep food and ingredients chilled.

The History of Refrigeration

Can you imagine owning a restaurant without having a refrigerator? Your costs would skyrocket, and your menu would be rather limited. That’s probably what the first inventors of “refrigeration” were thinking – way back in the prehistoric era. Ice houses were the first form of refrigeration.

Invented, probably, around 1700 BC, these were buildings that (shockingly) stored ice. Ice and snow were loaded into the building, then insulated with straw or sawdust, and then stored. While this works, it’s a bit cumbersome.

Mechanical Refrigeration

It wasn’t until 1756 that mechanical refrigeration became a real possibility. William Cullendemonstrated a rather impractical, but scientifically important, machine that created a small ice box by creating a partial vacuum over diethyl ether.

This jumpstarted the race to creating a mechanical refrigerator, and by 1834 there was a patent issued for a vapor-compression refrigeration cycle that did not rely on chemical solutions or volatile liquids.

Beginnings of Commercial Refrigeration

Commercial refrigeration caught on quicker than home refrigeration, which was a tougher sell. After all, consumers had to replace their trusty iceboxes, and the machines being produced during this early period weren’t particularly practical for the average home. Breweries and meat packing operations quickly fell in love with these machines though, and they saw widespread adoption.

Home Refrigeration

It wasn’t until 1914 that a practical, electric refrigerator was built for home use. Nathaniel B. Wales, of Detroit, MI, was issued the patent and it became the basis for the Kelvinator model. From there, refrigerators exploded in popularity. And obviously, you can find them in pretty much every residence in the country now

The Refrigeration Industry

During the 1900s, the number of commercial refrigerator manufacturers greatly increased. With advances in refrigeration, cooking and transportation, the commercial foodservice industry expanded across the country.

In the past, you may have found a tavern and a few local eateries – now, McDonald’s started appearing in every nook and cranny of the globe.

This was all made possible, in part, by efficient mechanical refrigeration for keeping food and ingredients at appropriate temperatures. So next time you eat a Big Mac, thank the commercial refrigeration company that makes it possible.

Theme 11.Centrifugation

1. 9

 1.Topical vocabulary:

2. Read and translate the text into your native language:

Centrifugation

Centrifugation and decantation (sedimentation, settling, flotation) are processes for the separation of heterogeneous mixtures of phases that differ from each other in their density. The physical principles governing these processes are the same.

Decantation occurs under the effect of earth’s gravity. In the case of centrifugation, accelerated separation is made possible by the effect of centrifugal forces, which may be many times stronger than earth’s gravity.

Centrifugation and decantation may be used to separate solid particles from a liquid or two immiscible liquids of different densities from each other, or both. Centrifugal separation is achieved not only with centrifuges but in any system where a rotational movement is imparted to the mixture. One of the devices for centrifugal separation without a mechanical centrifuge is the cyclone, discussed briefly at the end of this chapter. However, the major part of the present chapter will deal only with mechanical centrifugation and centrifuges.

Centrifuges are relatively expensive machines, both in capital expenditure and in the cost of operation (energy consumption, wear of rapidly moving parts, need for sturdy construction capable of resisting the very high forces and pressures).

Notwithstanding their cost, centrifuges are used extensively in industry. Following

are a few of the many applications of mechanical centrifugation in the food industry:

● Milk separation: one of the oldest and most widespread uses of the centrifuge in the food industry is the separation of whole milk to skimmed milk and cream. The centrifuges used for this purpose are known as ‘separators’ (Walstra et al., 2005)

● Cheese production: in modern dairy plants, centrifuges are used for the rapid separation of curd from whey

● Pulp control in fruit and vegetable juices: centrifugation is used for the reduction of pulp content in fruit juices and for the production of clear juices by total removal of the pulp

Centrifugation

● Edible oil processing: several operations in the production and refining of edible oils involve the separation of the oil from an aqueous phase. Centrifugation

is the preferred method of separation

● Essential oil recovery: essential oils of citrus fruit are recovered by centrifugal separation of aqueous mixtures formed in the course of juice extraction

● Production of starch: one of the methods for the separation of starch from suspensions is mechanical centrifugation

● Production of yeast: centrifuges are used for the separation of commercial yeast from the liquid growth medium.

Basic Principles

As stated above, centrifugation is a process of ‘accelerated decantation’. It is therefore advantageous to analyze first the process of ‘natural’ decantation in the field of earth’s gravity. The following discussion deals with the critical conditions for the separation of solid particles from a liquid. The same reasoning and the same results are also applicable to the separation of liquid droplets dispersed in a fluid.

Specific engineering issues concerning liquid–liquid separation will be discussed separately.

3. Translate the following sentences from  Russian into English:

1. Центробежная сепарация выполняется не только в центрифугах, но и в другой системе, где вращательное движение выделяет смеси.

2. Молочное разделение – один из старейших и наиболее распространенных видов использования центрифуги в пищевой промышленности является разделение цельного молока на обезжиренное молоко и сливки.

3. Производство сыра - в современных молочных заводах центрифуги используются для быстрого разделения творога от сыворотки.

4. ПрименениеPulp в фруктовых и овощных соках: центрифугирование используется для снижения содержания целлюлозы в фруктовых соках и для производства прозрачных соков путем полного удаления пульпы.

4. Answer the following questions:

1. What is the centrifugation?

2. Is there difference between centrifugation and decantation?

3. Could be the centrifugation used to separate solid particles from a liquid or two immiscible liquids of different densities from each other?

4. Point the devices for centrifugal separation without a mechanical centrifuge.

5. Is the centrifuges are cheap machines, both in capital expenditure and in the cost of operation?