Eleven brands of commercial black Kenyan tea leaves were
Eleven brands of commercial black Kenyan tea leaves were purchased and analyzed by gas chromatography/mass spectrometry to quantify the concentrations of 26 selected individual PAHs, using methods previously described . The measurements were conducted at the National Institute of Standards and Technology (NIST) in the Analytical Chemistry Division. Briefly, the tea samples were stored in their packages at room temperature until sub-sampled for analysis. SRM 2260a Aromatic Hydrocarbons in Toluene, SRM 1649a Urban Dust, SRM 2269 Perdeuterated PAH-I, and SRM 2270 Perdeuterated PAH-II were utilized from the Standard Reference Materials Group, NIST. One subsample from each brand of tea and one subsample from one bottle of SRM 1649a were placed into pressurized fluid extraction (PFE) Midostaurin (PKC412) containing hydromatrix (Isco, Lincoln, NE) and mixed with the hydromatrix. The void space of the cells was filled with hydromatrix. For the internal standards, a diluted solution prepared from SRM 2269 and SRM 2270 was added to each extraction vessel. The extraction used dichloromethane as a solvent heated for 5 min at 100 °C after preheating the cell for one minute. The PAHs of interest were quantified using gas chromatography/mass spectrometry.
These samples were analyzed at the same time as eight samples of yerba maté leaves from Brazil, the results of which have been previously published . For each PAH and the sum of all PAHs we calculated the mean and standard deviation of the 11 Kenyan brands and compared them to the means and standard deviations of the same PAHs in the 8 yerba maté brands.
Results One hundred subjects, including 78 men and 22 women, were interviewed in Bomet, Kenya. The median age of participants was 30.5 years, with a range of 18–78 years. All participants chose chai as their preferred beverage, and on average they reported drinking 4.2 (+1.9) cups of chai daily. The self-reported temperature for desired tea temperature was “warm”, “hot”, and “very hot”, 25%, 64% and 11% of participants, respectively. The reported length of time between pouring and drinking tea was > 4 min, 2–4 min, and <2 min for 29%, 49% and 22% (including 8 who said they drank their tea “immediately” after pouring) of participants, respectively (Table 1). The mean measured preferred chai temperature was 72.1 °C (+/−4.6) overall. The majority (88%) of the participants were from the local Kipsigis tribe and their mean preferred chai temperature was 72.2 °C (+/−4.6), which was non-significantly greater than the 70.8 °C (+/−4.2) mean preferred temperature of the 12 non-Kipsigis subjects (p = 0.33). There was no association between the mean preferred chai temperature and participant age; however, there was a statistically significant difference between men (72.6 °C +/−4.7) and women (70.2 °C +/−3.6) (p = 0.033) (Table 1). Kappa values showed moderate agreement between the two chai temperature-related questionnaire responses (weighted kappa = 0.541) and between each of these responses and the actual measured temperature categories (weighted kappas = 0.464 and 0.505) (Table 2). Table 3 shows the concentrations (ng/g of leaves) of benzo[a]pyrene (B[a]P), and the sum of all 26 selected PAHs in the 11 tested commercial brands of Kenyan black tea, and compares the mean (+/−SD) of these measures with the mean (+/−SD) of B[a]P and total PAHs in 8 commercial brands of Brazilian maté which were measured at the same time as the Kenyan tea.
Discussion Prior studies have demonstrated an association between ingesting hot temperature food and beverages and ESCC. This theory was first proposed by Watson in 1939 , but it was initially thought that the temperature of hot foods and beverages would not affect the esophagus after cooling rapidly in the upper digestive tract . However, De Jong and colleagues showed that drinking hot coffee (65 °C) could increase intra-esophageal temperature by 6–12 °C , and an endoscopic survey in southern Brazil demonstrated that drinking very hot maté was associated with esophageal injury (esophagitis) . Recent systematic reviews and meta-analyses have demonstrated an association between ingesting hot temperature food and beverages and ESCC [15,29,30]. A working group from the IARC has now classified very hot beverages as possibly carcinogenic [21,22].