STUDIES OF THE AGING OF FLUE-CURED CIGARETTE-LEAF TOBACCO PDF
Preview STUDIES OF THE AGING OF FLUE-CURED CIGARETTE-LEAF TOBACCO
THE PENNSYLVANIA STATE COLLEGE The Graduate School Department of Agricultural and Biological Chemistry STUDIES OF THE AGING OF FLUE-CURED CIGARETTE LEAF-TOBACCO A Thesis Seymour Stanton Block Submitted in Partial Fulfillment of the requirements for the degree of Doctor of Philosophy August, 19A2 Approved: W * .TftV Maj or^Prof essor Head of the Department TABLE OF CONTENTS LIST OF TABLES LIST OF FIGURES INTRODUCTION RESULTS OF PREVIOUS INVESTIGATIONS PREVIOUS TREATMENT OF TOBACCO A DESCRIPTION OF THE BACTERIA STUDIED DESCRIPTION OF METHODS EMPLOYED Chemical Steam Volatile Acidity Steam Volatile Bases Steam Volatile Neutrals Steam Volatile Aldehydes Determination of pH Potentiometric Measurements Qxidation-Reduction Potentials and Poising Effect Viscosimeter Measurements Moisture Relationships Determination of Reducing Sugars Bacteriological Determination of Bacterial Numbers Isolation and Morphology Utilization on Sugars Metabolism on Nitrogen Compounds PRESENTATION OF THE EXPERIMENTAL RESULTS DISCUSSION OF THE RESULTS SUMMARY AND CONCLUSIONS ACKNOWLEDGMENTS BIBLIOGRAPHY LEST OF TABLES I* Aging Samples of Flue-Cured Cigarette-Leaf Tobacco of the 1938 Crop II* Aged and Unaged Flue-Cured Cigarette-Leaf Tobacco Samples Used in These Studies III. The Total Steam-Volatile Acids and Bases, and pH of Aged and Unaged Flue-Cured Cigarette-Leaf Tobaccos IV. The pH of Aging Flue-Cured Cigarette-Leaf Tobaccos V. Potentioraetric Titrations of the Extract of Aged and Unaged Flue-Cured Cigarette-Leaf Tobaccos VI. The Drift in the Oxidation-Reduction Potentials of the Extract of Aged and Unaged Flue-Cured Cigarette-Leaf Tobaccos VII. The Drift in the Oxidation-Reduction Potentials of the Extract of Aged and Unaged Flue-Cured Cigarette-Leaf Tobaccos VIII. Viscosimeter Measurements on Aged and Unaged Flue- Cured Cigarette-Leaf Tobaccos IX. Moisture-Holding Capacities of Aged and Unaged Flue- Cured Tobaccos X. Bacteriological Assay of Aging Flue-Cured Cigarette- Le^f Tobaccos XI. Bacteriological Morphology of Aging Flue-Cured Cigarette- Leaf Tobaccos XII. Bacteriological Assay of Virginia Cigarette-Leaf Tobacco from Flue-Curing to One Year of Aging XIII. The Development of Molds on Aged and Unaged Flue-Cured Cigarette-Leaf Tobaccos after Exposure for One Week Over Distilled Water at Room Temperature XIV. The Rate of Reproduction of Bacteria Isolated from Aging Flue-Cured Cigarette-Leaf Tobaccos in Media Containing Pure Organic Nitrogen Compounds XV. The Oxidation-Reduction Potentials and Drift in Potentials of Aged and Unaged Flue-Cured Cigarette-Leaf Tobaccos LIST OF FIGURES The Distillation Apparatus for the Determination of the Volatile Constituents of Tobacco Potentiometric Titrations of the Extract of Aged and Unaged Flue-Cured Cigarette Tobacco The Drift in the Oxidation-Reduction Potentials of the Extract of Aged and Unaged Flue-Cured Cigarette Tobaccos The Effect of the pH on the Oxidation-Reduction Potential of Tobacco Extract Sample No. 361 Mold Growth on Aged and Unaged Flue-Cured Cigarette-Leaf Tobaccos After Exposure Over Distilled Water for One Week at Room Temperature The Utilization of Mono- and Disaccharides by Types of Bacteria Isolated from Aging Flue-Cured Cigarette-Leaf Tobaccos INTRODUCTION AND RESULTS OF PREVIOUS INVESTIGATIONS INTRODUCTION Before flue-cared tobacco is ready to be manufactured into cigarettes there elapses a period from two to three years of Maging.” During this process of aging there develops in the tobacco the aroma and mildness necessary for good smoking* As well as causing the tobacco producer to risk buying for a market three years hence, there is the expense and care connected with the storage of the tobacco. To add to the uncertainty is the natural quality of diff- t erent tobaccos with respect to the aging process* Some tobaccos age much more readily than others, and some will not age properly. These are some of the problems of the tobacco manufacturer with regard to aging of tobacco* If the changes that occur during the aging process are better understood, there appears some hope that the problems involved might be solved and the tobacco industry become more secure. The present studies have been undertaken with this consideration in mind. The chief purposes of these investigations ares 1) To study some of the chemical, physical, and bacteriological changes that occur in tobacco leaves as a result of the aging process; 2) To establish definite methods for recognizing and ascertaining the degree of aging undergone by the tobacco; 3) To suggest, if possible, some of the mechanisms which may be re sponsible for the desirable changes that occur during aging; 4) To reveal new methods and techniques for studying the problems of aging so that future investigations may be facilitated. 3 RESULTS OF PREVIOUS INVESTIGATIONS The scientific information available on the aging of flue- cured cigarette tobacco is unfortunately very meager; the greater portion of the work along these lines having been done on the "fer mentation" of cigar-leaf and chewing tobacco. It has often been necessary, therefore, to translate these results, as far as is possible, to the process of aging of cigarette-leaf tobacco. Since the fermentation and aging processes are decidedly unlike, it must be pointed out that any conclusions carried over from the former process to the latter are very likely to be invalid. It must be noted, however, that many of the earlier workers did not distinguish between these two processes but regarded them together as “fermentation." The views with regard to the fermentation and aging proces ses generally fall into three distinct categories. They include those conceptions which explain the above processes on the basis of 1) changes that occur as a result of purely chemical oxidations of the leaf constituents; 2) changes that occur due primarily to the action of the microorganisms on the tobacco leaves; and 3) changes which result from the action of enzymes which originate in the plant tissue. The literature will be reviewed with regard to these three viewpoints, respectively. Nessler (26) (27), in 1867, advanced the theory that under the proper conditions fermentation can occur in the absence of u enzymic or microbial activity* Boeckhout and Ott de Vries (5) for warded the theory that the fermentation was a purely chemical process activated by the oxygen of the air and added that iron of the plant acts as a catalyst for the oxidation* According to Loew (23), ‘’repeated efforts have been made to replace the sweating or fermentation process by a direct oxidation. Dr. Mew, of the Army Medical Museum in Washington, assures the writer that experiments made by him about twenty years ago to improve the cured tobacco leaf by direct application of a dilute solution of potassium per manganate resulted in an essential improvement. Similar results have also been mentioned by Kiessling (19). In Germany a patent has been granted by the firm of S iemens and Halske for treating tobacco with ozone.'’ The absorption of oxygen by yellow tobacco in the process of fermentation has been used as a measure of the fermentation by Smirnov (39) and is called "the oxygen number". The most recent and staunchest support of the chemical oxi dation theory, with respect to flue-cured cigarette tobacco, is given by Dixon et al (7) of Duke University. These workers are convinced, as a result of their experiments on aging tobacco, that bacterial, fungous, and enzymic action, if at all related to the aging process, certainly play a minor role. They suggest the mechanism that during aging there is a reaction between the sugars and amino acids of the leaf to produce "melanoidins", (1), with the liberation of carbon dioxide. Favoring this theory they find 1) significant losses of amino nitrogen and reducing sugars during aging, 2) melanoidins made
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