Taste thresholds to bitter compounds during a submarine patrol. Rep. No. 538.

Polaris submarines make two-month patrols and are submerged without external ventilation during the entire time. The atmosphere is controlled to maintain habitability using CO, COL> and H2 removers, as well as, 02 generators. The ambient COis elevated during the entire patrol to an average level of 1.0%. In general, the atmospheric trace components of this closed environment are expected to differ from those found under normal environmental conditions. Past study has indicated a decrease in the taste threshold for the sour modality aboard submarines. This study was undertaken to test the effect of this atmosphere on the bitter modality threshold. Taste thresholds for quinine (bitter) were determined during the refit period while in port and used as a baseline. Three subsequent taste tests were accomplished during the patrol at about two week intervals. A borderline statistically significant decrease in taste threshold (more sensitive) for quinine was noted. A consistently higher threshold was noted in smokers than in non-smokers. TASTE THRESHOLDS TO BITTER COMPOUNDS DURING A SUBMARINE PATROL INTRODUCTION Hutchinson (5) studied the changes in taste threshold for sour, salt, and sweet during two FBM* patrols. In his studies he found no change in the taste threshold for sweet and salt but did report a significant decrease in the taste threshold for sour. These findings, however, were not corroborated by Summitt (10) in a similar taste study in connection with a dietary survey. It was postulated by Hutchinson that the cause of the change in threshold may have been due to the increase in atmospheric carbon dioxide, (C02) that is present during the closed atmospheric conditions of a twomonth patrol. He also cited unpublished work that demonstrated increased salivary COo in individuals exposed to elevated ambient C02 in the 1.0 — 1.5% range. FBM Polaris submarine patrols are conducted in two phases. The first phase is known as the upkeep period, when the submarine is moored next to the Submarine Tender, and this period lasts about thirty days. Phase two is a sixty-day period of active submerged patrol, during which time the atmosphere is closed and continuously rejuvenated by C02, CO and H2 removal and 02 introduction. C02 levels on the USS ULYSSES S. GRANT (SSBN 631) (Blue) averaged 0.95% while CO was less than 15 PPM. Oxygen normally ran around 155 mm Hg with only traces of H2 present. Many other trace contaminants are also known to be present. The effect of this environment on the sensations of smell and taste has been a matter of some interest in regard to the food preferences and habits of submarine personnel. Since the bitter taste modality has been reported to be related to food preference (1, 3) this study was undertaken to discover if any changes could be detected during an FBM patrol. * FBM — Fleet Ballistic Missile (equipped with Polaris missiles) MATERIALS AND METHODS Twenty subjects were selected randomly from the crew of the USS ULYSSES S. GRANT (SSBN 631) (Blue) to participate in the experiment to determine their thresholds to quinine, and whether or not this threshold changed during the patrol. They were all informed of the purpose of the experiment and were acquainted with the procedures to be followed in its execution. The baseline threshold for quinine was determined during the refit period. The subjects were instructed as to the taste they should expect and the best manner in which to elicit this taste. They were given a sample of more concentrated quinine than that used in the test to become familiarized with the taste. It was suggested to them that they take the liquid into their mouth rolling it as far to the back of their mouth as possible. Each subject was presented with three solutions in cups labeled A, B and C. After tasting each solution they were asked which cup contained the bitter substance. If the subject was not sure, further instruction was given, as well as, the admonition not to guess but rather to inform the tester that he was not sure. The solutions were repeated each time presenting a weaker concentration until the subject was unable to consistently identify the quinine solution from the distilled water solutions in the other two cups. Each subject was then retested three times during the patrol at two week intervals. The same procedure was used as in determining the baseline threshold. Preparation on the quinine solutions was accomplished by dissolving .07469 gm of quinine sulfate into 100 ml of distilled water to make a .001 M solution. This was designated the Stock solution and was used to make all subsequent dilutions throughout the experiment. Ten ml of the Stock solution was diluted to make 100 ml giving a .0001 M solution which was designated as working stock #1. One ml of the stock solution was then diluted to make 100 ml giving a .00001 M solution designated as working stock #2. Further dilutions of the working stock solutions were then accomplished to make solutions of quinine sulfate from .6 X 10M to 11 x 10M which were then used in the threshold testing. For example, the 2.0xlO M solution was prepared by taking 2 ml of the working stock #1 and diluting it to make 100 ml. Further information about each subject was then compiled. This included smoking habits, number of years the subject has smoked, change in smoking habits during the patrol and the subject's age. RESULTS Examination of the raw results listed in Table I indicates several things. There were two main groups with high thresholds comprising one, and low thresholds in the other. Neither group demonstrated any dramatic effects from the patrol. Non-smokers demonstrated a consistently lower taste threshold than smokers, with these differences being significant (P < .05) for all test periods (t test). The pure threshold of non-smokers did not seem to be affected by the submarine atmosphere. However, the thresholds for smokers decreased as the patrol progressed, but the differences were not statistically significant between test periods. The differences between taste thresholds of smokers and non-smokers are graphically depicted in Figure 1. The line graphs connect the mean values and the vertical lines with assigned limits represent the standard error of the mean for each test period. Table II illustrates the differences between smokers and non-smokers, as well as, a comparison of all subjects. The average taste threshold decreases from 3.58xlO"M to 2.22 x 10M during the patrol. These differences are of borderline statistical significance Table I. — Taste Thresholds and Smoking Histories Bitter Taste Threshold (all X 10") Smoking History Subject June 21 July 12 July 2G Aug. 12 Age Number of Years Amount Habit Change 1 .8 .8 .8 .8 27 0 — — 2 9 9 9 11 26 7 2/d quit 9 July 67 3 9 9 10 9 24 5 1/d NONE 4 .8 .8 2 2 20 5 %/d NONE 5 .8 .8 .8 .8 24 0 — — 6 .8 .8 .8 .8 24 12 1%/d NONE 7 .8 .8 .8 .8 20 11 1/d NONE 8 .8 .8 .8 .6 26 0 — — 9 .8 .8 5 1 20 0 — — 10 7 2 1 1 19 6 1%/d NONE 11 6 .8 .8 .8 27 14 %/d NONE 12 .8 .8 .8 .8 23 10 %/d NONE 13 .8 .8 .8 .6 27 0 — — 14 .8 .8 .8 .8 19 0 — — 15 5 .8 .8 1 20 5 1%/d NONE 16 9 .8 .8 .8 30 13 1/d NONE 17 .8 .8 .8 .6 19 0 — — 18 8 9 6 7 32 18 2/d NONE 19 .8 .8 .8 .8 18 1% %/d NONE 20 9 9 10 4 27 9 1/d NONE