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1991 | Buch | 2. Auflage

Fundamentals of Food Process Engineering

verfasst von: Romeo T. Toledo

Verlag: Springer US

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Über dieses Buch

Ten years after the publication of the first edition of Fundamentals of Food Process Engineering, there have been significant changes in both food science education and the food industry itself. Students now in the food science curric­ ulum are generally better prepared mathematically than their counterparts two decades ago. The food science curriculum in most schools in the United States has split into science and business options, with students in the science option following the Institute of Food Technologists' minimum requirements. The minimum requirements include the food engineering course, thus students en­ rolled in food engineering are generally better than average, and can be chal­ lenged with more rigor in the course material. The food industry itself has changed. Traditionally, the food industry has been primarily involved in the canning and freezing of agricultural commodi­ ties, and a company's operations generally remain within a single commodity. Now, the industry is becoming more diversified, with many companies involved in operations involving more than one type of commodity. A number of for­ mulated food products are now made where the commodity connection becomes obscure. The ability to solve problems is a valued asset in a technologist, and often, solving problems involves nothing more than applying principles learned in other areas to the problem at hand. A principle that may have been commonly used with one commodity may also be applied to another commodity to produce unique products.

Inhaltsverzeichnis

Frontmatter
1. Review of Mathematical Principles and Applications in Food Processing
Abstract
A variable is a quantity that can assume any value. In algebraic expressions, variables are represented by letters from the beginning and end of the alphabet. In physics and engineering, any letter of the alphabet and Greek letters are used as symbols for physical quantities. Any symbol may represent a variable if the value of the physical quantity it stands for is not fixed in the statement of the problem. In an algebraic expression, the letters from the beginning of the alphabet often represent constants, that is, their values are fixed. Thus, in the expression ax = 2by, x and y represent variables and a and b are constants.
Romeo T. Toledo
2. Units and Dimensions
Abstract
The units used to designate magnitude of a dimension have evolved based on common usage and the instruments available for measurement. Two major systems for measurement have been used: the English system, used primarily in industry, and the metric system, used in the sciences. The confusion that resulted from the use of various terms to represent the same dimension led to the development of a common system of units that is proposed for use in both science and industry. The international system of units and the official international designation SI were adopted in 1960 by the General Conference on Weights and Measures. This body consists of delegates from member countries of the Meter Convention and meets at least once every six years. At least 44 countries are represented in this convention, one of which is the United States.
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3. Material Balances
Abstract
Material balance calculations are employed in tracing the inflow and outflow of material in a process, and thus establish the quantities of various materials in each process stream. The procedure is useful in making formulations, evaluating final compositions after blending, evaluating yields, and evaluating separation efficiencies in mechanical separation systems.
Romeo T. Toledo
4. Gases and Vapors
Abstract
Gases and vapors are naturally associated with foods and food processing systems. The equilibrium between food and water vapor determines the temperatures achieved during processing. Dissolved gases in foods such as oxygen affect shelf life. Gases are used to flush packages in order to eliminate oxygen and prolong shelf life. Modified atmospheres in packages are used to prolong the shelf life of packaged foods. Air is used for dehydration. Gases are used as propellants in aerosol cans and as refrigerants.
Romeo T. Toledo
5. Energy Balances
Abstract
Energy used to be a term everybody took for granted. Now, to a layman, energy has been added to the list of the basic necessities of life. Increasing energy costs have forced people to recognize and appreciate the value of energy more than ever before. Energy conservation is being stressed not only in industrial operations but also in almost all aspects of an individual’s daily activities.
Romeo T. Toledo
6. Flow of Fluids
Abstract
Fluids are substances that flow without disintegration when pressure is applied. This definition of a fluid includes gases, liquids, and certain solids. A number of foods are fluids. In addition, gases such as compressed air and steam are also used in food processing, and they exhibit resistance to flow just as liquids do. In this chapter, the subject of fluid flow will be discussed from two standpoints: (1) the resistance to flow and its implications for the design of a fluid-handling system and (2) evaluation of the rheological properties of fluid foods.
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7. Heat Transfer
Abstract
Heat transfer is the movement of energy from one point to another by virtue of a difference in temperature. Heating and cooling are manifestations of this phenomenon, which is utilized in industrial operations and domestic activities. Increasing energy costs and, in some cases, inadequate availability of energy will require peak efficiency in heating and cooling operations. An understanding of the mechanisms of heat transport is needed to recognize the limitations of heating and cooling systems. This understanding can lead to adoption of practices which circumvent these limitations. In industrial and domestic heating and cooling, energy use audits can be used to determine total energy use and the distribution within the process, to identify areas of high energy use, and to target these areas for energy conservation measures.
Romeo T. Toledo
8. Kinetics of Chemical Reactions in Foods
Abstract
Chemical reactions occur in foods during processing and storage. Some reactions result in loss of quality and must be minimized, while others produce a desired flavor or color and must be optimized to obtain the best quality. The science of kinetics involves the study of chemical reaction rates and mechanisms. An understanding of reaction mechanisms coupled with quantification of rate constants will facilitate the selection of the best conditions of a process or storage so that the desired characteristics will be present in the product.
Romeo T. Toledo
9. Thermal Process Calculations
Abstract
Inactivation of microorganisms by heat is a fundamental operation in food preservation. The concepts presented in this chapter are applicable not only in canning but in any process where heat is used to inactivate microorganisms and induce chemical changes which affect quality. The term sterilization, as used in this chapter, refers to the achievement of commercial sterility, defined as a condition in which microorganisms which cause illness, and those capable of growing in food under normal nonrefrigerated storage and distribution, are eliminated.
Romeo T. Toledo
10. Refrigeration
Abstract
Cooling is a fundamental operation in food processing and preservation. Removal of heat may involve either the transfer of heat from one fluid to another or from a solid to a fluid, or it may be accomplished by vaporization of water from a material under adiabatic conditions. Knowledge of the principles of heat transfer is an essential prerequisite to the understanding of the design and operation of refrigeration systems.
Romeo T. Toledo
11. Evaporation
Abstract
The process of evaporation is employed in the food industry primarily as a means of bulk and weight reduction for fluids. It is used extensively in the dairy industry to concentrate milk; in the fruit juice industry to produce fruit juice concentrates; in the manufacture of jams, jellies, and preserves to raise the solids content necessary for gelling; and in the sugar industry to concentrate sugar solutions for crystallization. Evaporation can also be used to raise the solids of dilute solutions prior to spray or freeze drying.
Romeo T. Toledo
12. Dehydration
Abstract
Dehydration is an important method of food preservation. The reduced weight and bulk of dehydrated products and their dry shelf stability reduce product storage and distribution costs. As dehydration techniques that produce good-quality, convenient foods are developed, more dehydrated products will be commercially produced. At present, instant beverage powders, dry soup mixes, spices, and ingredients used in further processing are the major food products dehydrated.
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13. Physical Separation Processes
Abstract
Food technology has evolved from the practice of preserving products in much the same form as they occur in nature to one where desirable components are separated and converted to other forms. Separation processes have been in use in the food industry for years, but sophistication in their use is a fairly recent occurrence. Current technology makes it possible to remove haze from wine and fruit juices or nectars, separate the proteins of cheese whey into fractions having different functional properties, separate foreign matter from whole or milled grains, and concentrate fruit juices without having to employ heat. Efficient separation processes have been instrumental in making economically viable the recovery of useful components from food processing wastes.
Romeo T. Toledo
14. Extraction
Abstract
One area of food processing which is receiving increasing attention is extraction. This separation process involves two phases. The solvent is the material added to form a phase different from that in which material to be separated was originally present. Separation is achieved when the compound to be separated dissolves in the solvent while the rest of the components remain where they were originally. The two phases may be solid and liquid, immiscible liquid, immiscible liquid phases, or solid and gas. Solid-liquid extraction is also called leaching. Supercritical fluid extraction is a recent development which involves a solid and a gas at supercritical conditions. Extraction has been practiced in the oil industry for a long time. Oil from soybean, corn, and rice bran cannot be separated by mechanical pressing; therefore, solvent extraction is used for their recovery. Oil from peanuts is recovered by mechanical pressing and extraction of the pressed cake to remove the oil completely. One characteristic of solvent-extracted oilseed meal is the high quality of the residual protein, which is suitable for further processing into food grade powders. It may also be tex-turized to form food protein extenders.
Romeo T. Toledo
Backmatter
Metadaten
Titel
Fundamentals of Food Process Engineering
verfasst von
Romeo T. Toledo
Copyright-Jahr
1991
Verlag
Springer US
Electronic ISBN
978-1-4615-7052-3
Print ISBN
978-1-4615-7054-7
DOI
https://doi.org/10.1007/978-1-4615-7052-3