Chapter 29
pH Changes in Smokeless Tobaccos Undergoing Nitrosation 1,2
1,2
3
R. A. Andersen , P. D. Fleming , T. R. Hamilton-Kemp , and D. F. Hildebrand
Downloaded via TUFTS UNIV on August 5, 2018 at 13:10:00 (UTC). See https://pubs.acs.org/sharingguidelines for options on how to legitimately share published articles.
2
1
Agricultural Research Service, U.S. Department of Agriculture, Department of Agronomy, University of Kentucky, Lexington, KY 40546-0091 Department of Agronomy and Department of Horticulture, University of Kentucky, Lexington, KY 40546
2
3
A previous study of moist and dry snuff indicated that nitrosated pyridine alkaloids accumulated at higher rates during storage at ca 50% moisture and 32°C as compared to less than 22% moisture and 24°C. Nitrite levels increased under these conditions but alkaloids such as nornicotine and nicotine decreased in concentrations (1). Ghabrial (2) determined that air-cured burley tobacco incubated at 35°C and 30-40% moisture underwent a sharp increase in bacterial counts within 1 week. An increase in pH of the leaf followed the rise in bacterial counts. The purpose of our present investigation was to determine whether pH changes in smokeless tobaccos accompany nitrosation reactions during prolonged storage. After chewing tobacco was stored for 48 weeks at each of four % moisture -temperature combinations (22.3%-24°C; 49.3%-24°C; 22.3%-32°C and 49.3%32°C) pH levels in each combination decreased from 0-time values. The largest decrease was at 49.3 %-32°C with increasingly smaller decreases observed in the following order: 22.3%-32°C, 49.3%-24°C and 22.3%-24°C. Chewing tobacco
underwent little change in amounts of nitrite Ν and total nitrosated alkaloids in all four storage treatments. Storage of dry snuff at each of four similar % moisturetemperature combinations for 24 weeks resulted in some significant changes in pH, niLite and N-nitroso compounds. pH levels and concentrations of nitrite and nitrosated alkaloids were higher in the stored high moisture dry snuffs but not in the low moisture counterparts at both temperatures. The pH's and concentrations of nitrite Ν and nitrosamine alkaloids in moist snuffs stored for 24 weeks at 55.5% moisture-24 or 32°C were markedly higher than in 21.9% moisture-24 or 32°C storage environments. Moisture-temperature interactions were observed in the high moisture-containing moist snuffs and dry snuffs. Chewing tobacco pH as a function of storage time decreased with increasing duration for each moisture-temperature treatment; the greatest magnitude of change occurred in tobacco stored at 49.3% moisture-32°C and the least change occurred in tobacco at 22.3% moisture-24°C. Dry snuff pH's at the 51.4% moisture level
0097-6156/94A)553-O320$08.00A) © 1994 American Chemical Society
Loeppky and Michejda; Nitrosamines and Related N-Nitroso Compounds ACS Symposium Series; American Chemical Society: Washington, DC, 1994.
29. ANDERSEN ET AL.
pH Changes in Smokeless Tobaccos
321
increased from 6.2 to an average final value of 8.0 at 48 weeks storage. Dry snuff stored at 12.3% moisture decreased from 6.2 to an average of 6.0 at 48 weeks. pH values of moist snuff stored at 55.5% moisture gradually increased from an initial value of 6.9 to an average final value of 7.2 at 48 weeks. Moist snuff at 21.9% moisture decreased from an initial pH of 6.7 to 6.4 at 48 weeks. To test the hypothesis that increases of tobacco nitrosamines are mediated by bacterial growth at near neutral pH, we heated snuff tobaccos in a manner analagous to pasteurization prior to storage to determine whether chemical and pH changes associated with accumulations of nitrosamines would lessen after heating. There were no significant changes in pH and the chemical parameters in heat-treated dry snuff after 24 weeks storage at 51.4% moisture-24 or 32°C compared to 0-time controls. Significant increases in pH, total nitrosamines and nitrite were found for nonheat-treated dry snuff after 24 weeks storage in the same manner. As shown in Table I, significant increases in pH, total nitrosamines and nitrite were found for nonheat-treated moist snuff stored at 55.5% moisture at 24°C compared to 0-time controls. Heat pretreatment of moist snuff stored in the same manner did not differ from 0-time controls. In summary: 1) pH's of high moisture content moist snuff (55.5%) and dry snuff (51.4%) increased 0.3 to 2.1 pH units during 48-week storage, 2) pH's of low moisture content moist snuff (21.9%) and dry snuff (12.3%) decreased (0.2 to 0.4 pH units) during 48-week storage, 3) pH's of chewing tobacco at each moisturetemperature treatment decreased during 48-week storage, 4) nitrosated alkaloids increased only in smokeless tobaccos that became more alkaline during storage, and 5) heat treatment of high moisture-containing snuffs at 100°C for 30 min just before storage prevented increases of pH, nitrosamines and nitrite that occurred in non-heattreated controls after 24-week storage. Table I. After Storage Effects of 30-Min Heat Treatment at 0-Time Storage on Moist Snuff (55.5% Moisture-24°C) Heat treat? yes/no
°C
Weeks stored
pH
0 24 24
6.9 A* 6.8 A 7.2 Β
Total nitrosated alkaloids
Nitrite-N ug/g....
no yes no
ambient 24 24
12.8 A 5.8 A 1203 Β
38.0 A 9.9 A 532 Β
•Means followed by different letter in column differ at ρ=05 REFERENCES 1.
Andersen RA, Fleming PD, Burton HR, Hamilton-Kemp TR, Sutton TG J Agric Food Chem, 1991, 39:1280-1287
2.
Ghabrial SA Tobacco Science, 1976, 20:95-97
R E C E I V E D January 26, 1994
Loeppky and Michejda; Nitrosamines and Related N-Nitroso Compounds ACS Symposium Series; American Chemical Society: Washington, DC, 1994.
