Objective To investigate the difference of hydrogen isotope ratio between whole grains and cereals flour and their components and the influence of drying conditions and moisture on the determination of hydrogen isotope ratio in grains and cereals. Methods High temperature cracking/elemental analysis-stable isotope ratio mass spectrometry (TC/EA-IRMS) was used to determine the δ2H values of whole grains and cereals flour (maize, rice, wheat and sorghum) and the fractions (starch, defatted portion, fat, crude fiber and protein). The effects of different drying conditions on the δ2H values of grain were analyzed, and the influence of exchangeable hydrogen on the determination of starch hydrogen isotope ratios was explored. Results The δ2H values of various fractions in the grains and cereals were different. Drying the grain samples at 105 °C to a constant weight was the best water removal effect. After being treated with different standard water samples under the optimal drying conditions, the maximum difference in δ2H of grains and starch was 12.11‰ and 18.41‰. This indicates that exchangeable hydrogen had a significant effect on the δ2H value of starch (P<0.001). Conclusion The isotopic fractionation of sugar, fat, protein and cellulose during the growth of grain makes the distribution of hydrogen isotopes in samples not uniform. Organic compounds contain exchangeable hydrogen, which will exchange isotopes with the water in the environment where the sample is located, affecting the accurate analysis. When measuring the hydrogen isotope ratio in grain, it is necessary to exclude the interference of water. This study provides an effective reference for the determination of hydrogen isotope ratios in grain starch and the study of grain traceability in the future.
| 科 Family | 属数 Number of genus | 种数 Number of species | 占总种数比例 Percentage of total species (%) | 属 Genus | 种数 Number of species | 占总种数比例 Percentage of total species (%) |
|---|---|---|---|---|---|---|
| 鹅膏菌科Amanitaceae | 2 | 11 | 5.26 | 鹅膏菌属 Amanita | 10 | 4.78 |
| 小菇科 Mycenaceae | 2 | 12 | 5.74 | 丝盖伞属 Inocybe | 5 | 2.39 |
| 多孔菌科 Polyporaceae | 8 | 14 | 6.70 | 蜡蘑属 Laccaria | 5 | 2.39 |
| 红菇科 Russulaceae | 3 | 23 | 11.00 | 小皮伞属 Marasmius | 6 | 2.87 |
| 小菇属 Mycena | 11 | 5.26 | ||||
| 光柄菇属 Pluteus | 5 | 2.39 | ||||
| 红菇属 Russula | 17 | 8.13 | ||||
| 栓菌属 Trametes | 5 | 2.39 |