粮谷中氢稳定同位素的影响因素研究

Study on the influencing factors of stable hydrogen isotopes in grains and cereals

中文关键词:  粮谷  氢同位素  淀粉  可交换氢  产地溯源

英文关键词:grains and cereals  hydrogen isotopes  starch  exchangeable hydrogen  traceability of origin

中文摘要:

      目的 探究粮谷全粉及各组分间氢同位素比值的差异以及干燥条件和水分对粮谷中氢同位素比值测定的影响。方法 采用高温裂解/元素分析—稳定同位素比值质谱法(high temperature cracking/elemental analysis-stable isotope ratio mass spectrometry, TC/EA-IRMS)测定粮谷全粉(玉米、大米、小麦和高粱)及各组分(淀粉、脱脂部分、脂肪、粗纤维和蛋白质)的δ2H值, 分析不同干燥条件对粮谷中δ2H值的影响, 探讨可交换氢对淀粉氢同位素比值测定的影响。结果 粮谷籽粒与各组分中的δ2H值存在差异, 粮谷在105 ℃烘干至恒重后除水效果最佳。在最佳干燥条件下被不同标准水样处理后, 粮谷和淀粉的δ2H值最大差值分别为12.11‰和18.41‰, 这表明可交换氢对淀粉的δ2H值具有显著影响(P<0.001)。结论 糖、脂肪、蛋白质、纤维素在粮谷生长过程中存在同位素分馏, 使样品的氢同位素不是均一性分布。有机物中含有可交换氢, 会与样品所处环境中的水进行同位素交换, 影响准确分析, 测定粮谷氢同位素比值时需排除水的干扰。本研究为后续粮谷淀粉中氢同位素比值的测定及粮谷溯源研究提供了有效的参考依据。

英文摘要:

      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.