Processes and Technological Systems for Freezing of Foodstuff

Processes and Technological Systems for Freezing of Foodstuff

Vladimir Stefanovskiy (All-Russian Scientific Research Institute of Refrigerating Industry, Russia)
DOI: 10.4018/978-1-4666-8398-3.ch011
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The principles and methods of holistic understanding of the foodstuff freezing process, as well as structure, functioning and development of refrigeration systems are set out in this chapter. It is meant for students, post-graduate students and experts working in the field of improvement of processes and devices of refrigerating productions. This chapter represents a great interest and for science officers as careful studying of the questions stated in it will relieve them of failures and repetition of the errors which were taking place in Russia, and will help them to choose ways for effective research work in the field of conservation of foodstuff by freezing.
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Formation And Development History Of The Refrigeration Engineering And Foodstuff Preservation By Means Of Freezing

Development Stages of Refrigeration Engineering

The history of development of foodstuff preservation by freezing involves three stages.

  • 1st Stage: (From ancient times to the second half of XVII century) - it is the era of preservation of food by natural cold. That experience was passed from generation to generation throughout the millennia and was of primitive nature. The reasons of preservation of foods at low temperatures were unknown at that time.

  • 2nd Stage: (The second half of XVII century - the end of the XIX century) - the era of separate accumulation of knowledge about ways artificial reduction of temperature and about ways of preservation of foodstuff at low temperatures. The differentiation of knowledge related to these two directions is explained by different objects of research, specific methods and criteria of assessment of the received results.

For the first time the Neapolitan doctor, Athicus Tolcredus reported about the fact that he had artificially obtained low temperatures and the cooling effect of mix of ice and salt in 1607. Later, in 1662, the chemist Robert Boyle wrote the same.

The following principles have become the expression of need and physical laws established in the XVII ÷ XVIII centuries.

  • Principle 1. If a substance evaporates, boils, melts or sublimes, it requires heat input, which is taken from the frozen object.

  • Principle 2. Maximum cooling effect is achieved when the used substance is boiling.

  • Principle 3. The boiling point of the liquid depends on the pressure affecting the liquid. The less is the pressure, the lower is the boiling point.

In 1748, William Cullen had turned the water into ice for the first time by lowering the pressure in the laboratory refrigeration unit.

In 1810, John Leslie created the first absorption refrigeration unit that produced 6 pounds (2.72 kg) of ice per hour. At the time, people wanted to create a device to get ice, because the cooling was seen only with the aid of ice.

In 1834, Jacob Perkins patented and demonstrated the first steam compression refrigeration machine.

In 1844, John Gorrie discovered a new cooling method and built the first air refrigeration machine where the refrigeration effect was achieved by the expansion of compressed air.

In 1895, the K. Linde built the machine for production of liquid air, which operated on the principle of multiple application of the Joule-Thompson effect. Later (in 1902), J. Claude built the unit operating on a different principle - the adiabatic expansion of compressed gas from the impact of external work, which also paved the way for the development of industrial plant for liquefying air. Nevertheless, only after development of a way of division of liquid air into separate components by distillation and rectification, one of components of liquid air - liquid nitrogen - began to be used in industrial foodstuff freezing. Liquid nitrogen is neutral to the foodstuff and under atmospheric pressure, it boils at the temperature of minus 196°C.

Key Terms in this Chapter

Process of Freezing: Freezing of foodstuff is the process of lowering the product temperature below cryoscopy point, accompanied by turning the water in a product into ice during the removal of certain amount of heat from the product.

Principle of Complementarily: Means addition up to complete structure.

Frozen Foodstuff: The Foodstuff received as a result of freezing.

The Note: The Temperature of concrete type of the frozen product is established by technical regulations.

Technological Freezing System: The system is a set of the interconnected subsystems (1.The system of preparation of working medium; 2.The system of feeding and/-or movement of the freezing medium; 3.The system of placement and movement of the foodstuff; 4.The system of management) acting together for freezing of foodstuff.

Regular Regime when Freezing: Stage of process of freezing at which reduction of a mass fraction of unfrozen product in degree 1/3 varies with time under the linear law.

Shrinkage of Meat: The moisture which has evaporated from meat at the freezing, expressed in percentage of initial weight of a product.

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