[Advances in Food Research] Advances in Food Research Volume 17 Volume 17 || Tropical Fruit Technology

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<ul><li><p>TROPICAL FRUIT TECHNOLOGY BY N. CZYHRINCIW </p><p>Department of Chemistry and Technology, Faculty of Agronomy, Central Uniuersity, Maracay, Venezuela </p><p>I. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11. The Significance of Fruits . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . </p><p>111. Morphology and Anatomy of Fruits . . . . IV. Physical Properties of Fruits ............................................. 165 V. Some Chemical Properties of Fruits . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 174 </p><p>......................... 163 </p><p>A. Color, Aroma, and Flavor. ............................................ 174 B. Vitamins and Mineral Salts . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 179 C. Carbohydrates, Proteins, Fats, and Caloric Value ....................... 182 D. Enzymes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 183 E. Other Substances . . ........................... 185 </p><p>. . . . . . . . . . . . . . . . . . 185 A. Preservation of Fresh Fruits and Freezing.. ............................ 185 B. Separation of the Inedible Part (Skin). ................................. 188 C. Obtaining Juices, Pulps, and Concentrates ............................. 190 </p><p>................................... 194 E. Sweet Products. . . . . . . . . . . . . ................................... 195 F. Fermentation Products -Alcoholic and Acetic ......................... 196 G . Age of Elaborated Products ........................................... 199 H. Preservation by Irradiation ........................................... 204 </p><p>VII. Conclusion . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 204 References . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 207 </p><p>VI. Technical Problems ............................... </p><p>D. Dehydrated Products . . . . . . . . </p><p>I. INTRODUCTION </p><p>With the expansion of the food industries at the beginning of the twentieth century, the science of food technology was established for study of the preservation of edible agricultural products in their natural state, and for the study of cheap and practical methods of processing foodstuffs, to preserve them and improve their quality. </p><p>Processing is the series of manufacturing operations that transform the natural structure and change the proportions of the substances </p><p>153 </p></li><li><p>154 N . CZYHRINCIW </p><p>initially present in the raw materials. The science of food technology is concerned with study of the physical and chemical properties of the raw materials and the finished products, of the manufacturing processes, of the machinery used, and of the analyses used-organo- leptic, physical, chemical, and bacteriological. </p><p>Many modern industrial processes are based on ancient experience gained in primitive manufacturing and rural handicrafts. Desrosier (1961), for example, presented a historical survey of methods of cereal preservation known for thousands of years. H.: refers to the ancient civilizations of the Middle East, of India, of the Inca Empire in Peru, etc. Such products as salted and pickled fish, cured meats, fermented drinks, bakery goods, etc., were commonly sold in the markets of the Roman Empire. Storni (1942) reports that the ab- origines of South America had developed processes to preserve certain food products, and that they could manufacture flour, sweets, beverages, and other things. Friedman (1963) states that many of our established methods of food preservation and food processing come from prehistorical times, and their safety has been tested in the crucible of human experience, not always, however, definitively and with finality. </p><p>Studies in food technology cover various fields, characterized either by the nature of the raw materials (e.g., cereals, fruits, meats) or by the common processes of manufacturing and the resulting similarities in the finished products (e.g., bread baking, canning, bottling of soft drinks). </p><p>As a part of food technology we study fruits, particularly the prob- lems presented by tropical fruits. </p><p>The development of the several fields of food technology is very important in the social and economic life of all countries, as may be seen from the history of Australia, where the great boom in the past century in farming and stock raising was brought about by the develop ment of frozen-meat technology and canning industry, which made it possible for high-quality products at satisfactory prices to be exported to the markets of distant and thickly populated Europe. Peterson and Tressler (1963) consider the social and economic development of Australia to be almost an ideal case. </p><p>The industrialization of pineapple in Hawaii is another example of the significance of food technology. The growing and processing of pineapple in Hawaii has become a principal occupation of the people of the island. New, thoroughly mechanized factories produce 57% of the worlds canned pineapple and 82% of its pineapple juice (Cushing, 1960). </p></li><li><p>TROPICAL FRUIT TECHNOLOGY 155 </p><p>In the United States 28% of industry is concerned with food processing, employing 13.2 90 of the national working force (Parker et al., 1952). It may be noted that during the last twenty years, the consumption of frozen foods has increased eight times, and that of baby foods 42 times (Proctor, 1960). In England, the consumption of canned juices has increased 400% in the last five years. </p><p>The development of agriculture in distant areas would be im- possible without modern technology to preserve and process farm products. Desrosier (1961) has estimated that the present world population will have doubled in the next forty years, from three billion to six billion; the demand for foodstuffs will grow proportion- ally. Areas in the temperate zone suitable for growing wheat or rye will soon be totally occupied; meanwhile, huge areas suitable for rice and corn lie untouched in the tropics. Also, land suitable for growing the white sugar beet (Beta uulgaris) soon may not be avail- able. Although scientific research has increased the sugar content of this root from 6 to 18% within the last century, it does not seem probable that this can be carried any further. However, there is no shortage of space for growing sugar cane in the tropics. </p><p>Equally vast possibilities exist in the tropics for the cultivation of other crops, especially for fruit plants. Thus, a great future may be expected in tropical farming, and inevitably, a parallel develop- ment in tropical food technology. This advance in tropical farming will occur sooner than the production of synthetic foods mentioned by Proctor (1960), despite the fact that the cost of many synthetic vitamins has decreased by almost half during the last six years, according to Fox (1963). </p><p>Food technology must prepare in advance to respond to its future role as a principal factor in food production and processing. Desrosier (1961), in his absorbing book, has explained the possibilities of food production in the new tropical zones, and also its main technical difficulties. Wickiner (1960) has also discussed important aspects of farming in Asia, Africa, and Latin America. </p><p>Food technology, particularly fruit technology, in the tropics is determined by certain specific conditions. </p><p>(1) Natural fruit resources are potentially enormous. One recalls Humboldts calculation that the growing of 33 kg of wheat and 90 kg of potatoes requires the same ground area as the growing of 4000 kg ofbananas (Nicholls, 1901). </p><p>There are many obscure fruit plants in the wild or semi-primitive state. The time necessary for growing plants to the first crop is rela- tively short in the tropics; this is an important factor in planning and </p></li><li><p>156 N. CZYHRINCIW </p><p>forecasting needs for raw materials. For example, papaya and passion fruit trees start to bear at the end of the first year; cashew at the third year; the mango tree between the fourth and sixth years; and the coconut from five to eight years. Another advantage is that since fruit crops ripen at different times in the tropics the manufacturing processes can work on freshly harvested fruits almost all year long. </p><p>(2) Transport of harvests and technological processes are usually carried out at high temperatures. Van't Hoff established that every increase in temperature of 10C speeds chemical reactions two to three times. This necessitates special study on desirable or undesir- able biochemical processes, autoxidation, and, particularly, on tin- plate corrosion. Temperatures in production departments and storage houses always range between 22" and 32C. Other negative factors, such as strong sunlight and high seasonal humidity, affect the manu- facturing and storage of raw materials and elaborated products. </p><p>(3) In the future development of tropical-fruit technology, export to far markets should be taken into account. Such factors as the conditions of manufacturing and packaging the semifinished prod- ucts, as well as the stability of the exotic products, will be of great importance. </p><p>(4) It is probable that the products of a majority of tropical countries will be less contaminated by radioactive elements than the products of more northerly countries, as may be confirmed by comparative determinations of radioactive contamination made by Solanas et u1. (1964). </p><p>(5) Since the larger and more experienced research institutions have been located in temperate and subtropical climatic zones, different aspects of the technology of tropical fruits have not yet been properly studied. Only botanical data and data on the principal chemical substances contained are known for tropical fruits (INCAP- ICNND, 1961; Popenoe, 1938, 1939; Landaverde, 1941; Nicholls, 1901; Chandler, 1958; Castaiieda, 1961; Pittier, 1926; Sturrock, 1959; Kennard and Winter, 1963; Aristeguieta, 1950; etc.). </p><p>Among all tropical fruits, those most studied have been: the banana, by von Loesecke (1949) and Simmonds (1959); the pineapple, by Collins (1960); the mango, by Singh (1960); the passion fruit, by Pruthi (1963); and the coconut, by Child (1964). </p><p>There is a serious lack of knowledge and technical data on tropical raw materials and on the most suitable methods for their processing. Some of the data and technical methods currently available, and lines for further research will be covered in the following chapters. </p></li><li><p>TROPICAL FRUIT TECHNOLOGY 157 </p><p>II. THE SIGNIFICANCE OF FRUITS </p><p>Fruits are edible products, borne on the perennial higher plants, having agreeable sweet-sour and semiastringent flavors. Their water content is high, and they deteriorate easily. The texture of the mature tissues is relatively soft. Fruits develop, according to their position on the plant, in contact with the air, not with the soil. </p><p>The edible products of the fruit-bearing higher annual plants are called vegetables, e.g., tomatoes, red peppers, cucumbers. Melons and watermelons are a sweet class of vegetables that develop on the soil surface. Nuts, which are edible products of fruit-bearing plants, have an agreeable flavor, a high content of fat and protein, a reduced water content, and a hard texture when mature. The products of fruit- bearing plants with a very high content of aromatic essences are spices (pepper, coriander with 2% oil, cardamon with 343% oil, etc.). </p><p>The definition of fruit given by Websters International Un- abridged Dictionary states: There is no well-drawn distinction between vegetables and fruits in the popular sense; but it has been held by the courts that all those which, like potatoes, cabbage, peas, carrots, celery, lettuce, tomatoes, etc., are eaten (whether cooked or raw) with the principal part of the meal are to be regarded as vegetables; while those used only for desserts are fruits. This definition, quoted by Meyer (1960), deals more with the location of fruits within a dietetic dimension and in accord with popular experi- ence than with the technical definition of these important products. </p><p>Hughes (1962) gives the following definition for fruits: the foods commonly designated as fruits, however, are pulpy in character, often juicy, and since they develop from the flowers of plants, they consist of the ripened seed or seeds with some edible tissues at- tached. The famous Russian scientist F. W. Zerevitinoff stated 40 years ago that fruits are poetical and vegetables are prose inspira- tions in the human nutrition. </p><p>Rietz (1961), in his Gustametric Chart, classifies fresh fruits as a separate group of foods, placing them within the scale of taste inten- sity (which ranges from zero, for water, to 940, for red pepper) be- tween the numbers of 39 and 350. Most foods are included in this range, whole-wheat bread having a value of 12, and rum a value of 350. Thus, Rietz has confirmed one of the characteristics of fruits: fruits are foods with the widest range of flavor factors. </p><p>Within the taste-intensity scale given above, the best-known tropi- cal fruits have classification numbers shown in Table I. In com- parison, nontropical fruits are shown in Table 11. </p></li><li><p>158 </p><p>Papaya 39 Avocado 40 Cherimoya 44 Banana 48 </p><p>N. CZYHRINCIW </p><p>Mango 75 Guava 83 Pineapple 100 </p><p>Apples 52 Grapes 72 Oranges 122 </p><p>TABLE I1 CLASSIFICATION NUMBERS OF NONTROPICAL FRUITS </p><p>Lemon 260 Lime 350 </p><p>aCalculated from Gustametric Chart of Rietz (1961). </p><p>Desrosier (1959) has classified foods according to their acidity, putting the fruits into two groups, one of pH 4.5-3.7, and one a highly acid group of pH 3.7-2.3. </p><p>According to research of Ralls (1959), the specific flavor of cooked vegetables (green peas, red beets, spinach, canned asparagus) de- pends partially on acetoin and other products of its autoxidation. Acetoin is produced by glycol oxidation and is found in the fresh vegetables mentioned. It increases in content at the beginning of cooking. For instance, the content of acetoin in green peas cooked fifteen minutes may reach 340 ppm. The products of acetoin oxidation are also found in the baking of bread (75 ppm). Fresh and cooked fruits do not have such specific taste and aroma. Further studies of the above-mentioned substances would probably make possible more objective determinations of the characteristic differences between fruits and vegetables. </p><p>Because of their organoleptic and chemical properties, fruits, with their pronounced flavors, are consumed by man in relatively smaller quantities than are the simplest vegetable products, such as rice, potatoes, and beans. Fruits are eaten in the natural or the processed state; before meals to stimulate the appetite, or to slake the thirst; or as dessert after the main course, to cleanse the palate of the flavors of soup, fish, or meat. </p><p>Although of relatively low caloric value, frui...</p></li></ul>

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