[Advances in Food Research] Advances in Food Research Volume 3 Volume 3 || Electromagnetic Radiation Fundamentals and their Applications in Food Technology

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  • Electromagnetic Radiation Fundamentals and Their Applications in Food Technology

    BY BERNARD E . PROCTOR AND SAMUEL A . GOLDBLITH Department of Food Technology.

    Massachusetts Ins t i tu te of Technology. Cambridge. Massachusetts

    CONTENTS Page

    I . Introduction . . . . . . . . . . . . . . . . . . . . . . 120 I1 . Types of Radiation . . . . . . . . . . . . . . . . . . . 122

    1 . Sonic and Ultrasonic Vibrations . . . . . . . . . . . . . 123 2 . Radio Waves . . . . . . . . . . . . . . . . . . . . 123

    a . Dielectric and Induction Heating . . . . . . . . . . . 123 b . Radar Energy . . . . . . . . . . . . . . . . . 125

    3 . Infrared Radiations . . . . . . . . . . . . . . . . . 126 4 . Ultraviolet Radiation . . . . . . . . . . . . . . . . . 127 5 . X Rays (Gamma Rays) . . . . . . . . . . . . . . . . 127 6 . Cathode Rays (Beta Rays) . . . . . . . . . . . . . . . 129

    111 . Uses of Sonic a n d Ultrasonic Vibrations . . . . . . . . . . . . 130 I V . Uses of Radio-Frequency Heating . . . . . . . . . . . . . . 132

    1 . Sterilization . . . . . . . . . . . . . . . . . . . . 132 a . Mode of Action of Radio-Frequency Sterilization . . . . . 132 b . Destruction of Hoof and Mouth Virus . . . . . . . . . 133 c . Pasteurization of Wine and Beer . . . . . . . . . . . 133 d . Sterilization of Packaged Bread . . . . . . . . . . . 134 e . Destruction of Insects in Grain . . . . . . . . . . . 134

    2 . Blaiicliing of Foods . . . . . . . . . . . . . . . . . 136 3 . Defrosting of Frozen Foods . . . . . . . . . . . . . . 137 4 . Roasting of Coffee . . . . . . . . . . . . . . . . . . 138 5 . Baking and Cooking . . . . . . . . . . . . . . . . . 138 6 . Dehydration . . . . . . . . . . . . . . . . . . . . 142 7 . Moisture Determinations . . . . . . . . . . . . . . . 143 8 . MiscelIaneous Uses . . . . . . . . . . . . . . . . . . 143 9 . Economica of Radio-Frequency Heating . . . . . . . . . . 144

    V . Uses of Infrared Radiation . . . . . . . . . . . . . . . . 146 1 . Dehydration . . . . . . . . . . . . . . . . . . . . 146 2 . Flour Milling . . . . . . . . . . . . . . . . . . . . 146 3 . Protection of Fruits and Vegetables from Frost Damage . . . . 146 4 . I n Poultry Rearing . . . . . . . . . . . . . . . . . 147 5 . In Chemical Analysis . . . . . . . . . . . . . . . . . 147

    V I . Uses of Ultraviolet Light . . . . . . . . . . . . . . . . . 147 1 . Germicidal Action . . . . . . . . . . . . . . . . . . 147 2 . Aging of Meat . . . . . . . . . . . . . . . . . . . 152 3 . Activation of Provitamins D . . . . . . . . . . . . . . 153 4 . To Improve Coffee Flavor . . . . . . . . . . . . . . . 153

    119

  • 120 BERNARD E . PROCTOR AND SAMUEL A . OOLDBLITH 5 . As an Analytical Tool . . . . . . . . . . . . . . . . . 153 G . Detection of Infected or Washed Eggs . . . . . . . . . . . 154

    V I I . Uses of Radioactive Isotopes . . . . . . . . . . . . . . . . 155 1 . Germicidal Action . . . . . . . . . . . . . . . . . . 155 2 . Applications in Agriculture . . . . . . . . . . . . . . . 156

    V I I I . Uses of X Rays . . . . . . . . . . . . . . . . . . . . 156 1 . Germicidal Action . . . . . . . . . . . . . . . . . . 156 2 . Effect on Vitamins . . . . . . . . . . . . . . . . . . 157 3 . X-Ray Diffraction . . . . . . . . . . . . . . . . . . 158 4 . Fluoroscopy . . . . . . . . . . . . . . . . . . . . 158 5 . Destruction of Toxins . . . . . . . . . . . . . . . . 159 6 . Miscellaneous . . . . . . . . . . . . . . . . . . . . 159

    I X . Uses of Cathode Rays . . . . . . . . . . . . . . . . . . 160 1 . Germicidal Action . . . . . . . . . . . . . . . . . . 163 2 . Effect on Vitamins . . . . . . . . . . . . . . . . . . 167 3 . Effect on Amino Acids . . . . . . . . . . . . . . . . 174

    174 5 . Effect on Coffee and Its Components . . . . . . . . . . . 176

    180

    4 . Effect on Enzymes . . . . . . . . . . . . . . . . . . 6 . A s a Tool for Studying Some Chemical Reactions . . . . . . .

    a . Nonenzymatic Browning . . . . . . . . . . . . . . 180 b . Meclianism of Spoilage of Fish . . . . . . . . . . . 184

    7 . Effect on Packaging Materials . . . . . . . . . . . . . 187 8 . Effect o n Pharmaceuticals . . . . . . . . . . . . . . . 187 9 . Toxicity of Irradiated Materials . . . . . . . . . . . . . 187

    X . Summary . . . . . . . . . . . . . . . . . . . . . . . 188 Acknowlrclginrnts . . . . . . . . . . . . . . . . . . . . 189 References . . . . . . . . . . . . . . . . . . . . . . 189

    I . INTRODUCTION I t is well known that conventional means of heat processing irrevers-

    ibly alter the flavor. color. and texture of many foods . Usually altera- tions are advantageous. but for some products it would be desirable to have them less extensive . The changing food habits of American con- sumers have made many of these alterations acceptable. but there are some foods (especially fruits and vegetables) whose flavors are preferred in the fresh state .

    From the point of view of flavor alone. it is desirable to improve our present methods of processing foods . Some improvements have been made in this direction with a number of food products by use of high- temperature short-time processing . Much research has been conducted in recent years to ascertain whether it is possible to improve the color. flavor. and retention of nutrients in processed foods by means other than heat for processing . Among the alternative means that have been consid- ered to attain this objective in food processing is the utilization of several of the radiations of the electromagnetic spectrum . With the hope of added improvement. research is being conducted a t the present time by

  • FIG. 1. Illustrative chart of the electromagnetic spectrum, showing the approxi- mate locations o f various types of radiation. Roman numerals refer to main sections of report where uses of radiations are discussed; Arabic numbers refer to paragraphs of Section I1 describing the various types of radiation.

  • 122 BERNARD E. PROCTOR AND SAMUEL A. GOLDBLITH

    a number of laboratories in which electronic heating and cold steriliza- tion by electromagnetic irradiations are being employed.

    This review covers the known applications of electromagnetic energy in the field of food research within the past ten years, from sonic vibra- tions a t one end of the spectrum to gamma rays a t the other end. F o r orientation, some reference is made to previous applications. Although lack of space precludes complete citation of the earlier literature, this fortunately is adequately covered in the excellent treatise on the Bio- logical Effects of Radiations by Duggar (1936).

    To orient the reader, a n illustrative chart of the electromagnetic spec- t rum is presented in Fig. 1. This chart shows the approximate locations, in the electromagnetic spectrum, of the various types of radiation dis- cussed in this review. The Roman numerals refer to the sections of this paper where discussion of the uses of the various radiations may be found and the Arabic numbers to the paragraphs of Section I1 describ- ing the various types of radiation.

    I n an effort to make a logical presentation of the known applications of electromagnetic energy in the food field, this review has been divided into several sections. The first section contains a brief discussion of the various types of electromagnetic radiation. The subsequent sections are concerned with the applications of various types of radiation, each sec- tion being devoted to the uses and the potentialities of a specific type. The order in which the sections on radiations are presented is that in which the radiations occur in the spectrum, from long wavelengths to short wavelengths (Fig. 1) .

    11. TYPES OF RADIATION

    Infrared radiations, as well as the other types of electromagnetic radiations, are composed of packets of energy known as quanta. They consist of an electric and a magnetic vibration of high frequency, vibrations that travel in a straight line through space a t a velocity of 3 x 1O1O cm. per second. Electric and magnetic vibrations are always present together, each being associated with the other and perpendicular to the other.

    The difference between the members of the electromagnetic radiations is chiefly a difference in the frequency of the waves or vibrations or a difference in the energy of the wave packets. For example, if the fre- quency were lo1* cycles per second (corresponding to a photon energy of 7 x ergs), this frequency would be typical for infrared radia- tion. If the frequency were lo8 cycles per second (corresponding to a photon energy of 7 x ergs), the frequency would be characteristic of a radio wave.

  • APPLICATIONS OF ELECTROMAQNETIC RADIATIONS 123

    1. Xonic and Ultraso& Vibrations

    These radiations occur in the low-frequency range of the electromag- netic spectrum. A frequency of 20,000 cycles per second (20 kilocycles) is the upper limit fo;- waves within the range audible to the average human being. Frequencies as great as 500 megacycles have been gen- erated by methods recently developed. These radiations cover a tre- mendous range in both frequency and wavelength. For convenience, waves with frequencies up to 20 kilocycles per second are called sonic vibrations and those above, supersonic or ultrasonic vibrations. Sollner (1944) emphasized that there is no fundamental physical difference between ultrasonic and audible sound and that the difference in nomen- clature is based entirely on a physiological limitation in mans hearing ability.

    At the present time, a number of small ultrasonic generators are available on the market. The usual sonic or ultrasonic generator con- sists of some means of generating th

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