258 



National Resources Planning Board 



and carbon dioxide, and to the use of ozone. Investi- 

 gations on the method of extracting and preserving 

 fruit flavors for use in gelatin, ice cream, and candy are 

 being carried on in a number of industries. 



Freezing of foods is a large and rapidly growing 

 industry. Fruits and vegetables are being frozen 

 chiefly by quick freezing methods, although some fruits 

 are frozen more slowly. Ucvelopment of quick-freezing 

 methods has opened a large field of research by biol- 

 ologists, for fruits and vegetables suitable for canning 

 are not necessarily adapted to freezing, and old varieties 

 are being tested and new varieties sought. Inactivation 

 of enzymes, especially of those of vegetables, is being 

 investigated, for the enzymes are not destroyed by low 

 temperatures and may cause appreciable changes in the 

 frozen product. The chemical and physical changes 

 which take place between harvesting and thawing of 

 the frozen product before consumption also are receiving 

 the attention of biochemists and biophysicists. 



Most fruits are so acid that spoilage of the canned 

 product is not a major problem, although occasionally 

 difficulties arise in the preservation of such fruits by 

 drying. Physical and chemical changes in the plant 

 cells which take place during harvestmg, lye treatment, 

 sulfuring, drying, and "sweating" are subjects for 

 research. The treatment of fresh fruits to destroy 

 molds and bacteria may extend the marketing period. 



Vegetables. — The problems in connection with the 

 freezing of vegetables have been discussed under the 

 heading "fruits." Biologists have been helpful to the 

 canning industry in its packing of vegetables. The 

 production of vegetables suitable for canning has 

 inspired some important linos of research. A notable 

 example is the discovery that deficiency of soils in boron 



FniUHK SI. PliutuL-lc'clric Cipldriiiiilc r iiir MrasiiriiiK Aiiumiil 

 of Vitamin .A in Foods, Purina Mills, St. Louis, Missouri 



is responsible for "black heart" in caiming beets. 

 Geneticists and plant breeders are engaged in producing 

 new varieties, especially suited to processing and 

 shipping. 



Tlie canner is always torn between the desire to heat 

 the canned product as little as practicable, so as to 

 avoid harm to the quality of his product, and to admin- 

 ister a severe heat treatment to assure the inactivation 

 of all spoilage organisms. The bacteriologist has 

 studied the heat resistance of spoilage bacteria, the 

 sources of these organisms, and new methods of 

 processing. He is at present interested in the develop- 

 ment of the new high-temperature short-time methods. 



Fungi. — The cultivation of mushrooms, molds, 

 yeasts, and bacteria for use as foods is a large industry 

 in itself with many possibilities as yet unexplored. The 

 industry in the United States produces annually about 

 18 million pounds of muslu-ooms. This is a good illus- 

 tration of how sound biological methods make possible 

 great industries. The rapid growth of the mushroom 

 industry is mainly due to two biological processes, the 

 development of pure culture methods of growing 

 spawn and improvement in the preparation of compost 

 humus. 



Commercial yeast manufacture. — The cultivation of 

 yeasts for food, for various vitamins or vitamin pre- 

 cursors, for leavening of bread dough, for manufacture 

 of beer, wines and other foods and beverages has been 

 the basis of research by the biologists who are still 

 studying the physiological characteristics of yeasts and 

 efficient methods for their cultivation. Studies in this 

 field have thrown light on the chemical and physiological 

 processes in higher plants and animals. 



Manufacture of bacterial cultures. — Many food indus- 

 tries use pure cultures of bacteria and the preparation 

 of these cultures is a considerable industry in itself. 

 In the dairy industries starter cultures are needed for 

 the manufacture of cheese, butter, and fermented 

 milks. The production of special enzjmies not only from 

 bacteria but also from yeasts and molds for use in 

 food and other industries is increasing in importance. 

 The successful growth of leguminous crops such as 

 alfalfa, clover, peas, and soybeans, often depends 

 upon the use of suitable cultures of the nodule-forming 

 organisms — the symbiotic rhizobia. Obviously the 

 bacteriologist finds research necessary to determine 

 methods for the preparation of effective, long-lived 

 cultures which are able to perform the functions 

 expected of them. The growth of cultures for the 

 production of enzymes introduces problems not only 

 of yield but of isolation and purification of the product. 

 It is anticipated that research work on enzyme 

 products will continue to grow m importance. 



Cereals and cereal products. — The cereal industries 

 are faced with problems in grain production, processing, 



