Agave syrup has become a popular sweetener among consumers because of its low glycemic index and pleasant taste, but substitution by cheaper sugar syrups makes it vulnerable to fraud. A ¹³C site-specific natural isotopic fractionation (SNIF)-NMR approach had been developed to allow the detection of C₄ plants (cane, maize) in agave products, with the drawback of a long NMR acquisition time. In this work, an INEPT (insensitive nuclei enhanced by polarization transfer) pulse sequence was implemented to significantly reduce acquisition time while accurate and reproducible results are obtained. Apparent site-specific isotopic deviations were correlated to values acquired with single pulse method. The analytical method was validated following the normative procedure NF V03-110, from sample preparation to data correction. With a single pulse method as a reference, performances were at least equally good and measurement time was halved, opening new methodological ways for isotopic ratio monitoring of carbon in the ethanol molecule by NMR, also applicable to fermented and fermentable beverages. In parallel, the method was extended to agave inulin characterization after a preliminary controlled hydrolysis.

中文翻译：

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通过乙醇的同位素分子内 13C 含量鉴定龙舌兰产品：13C 定量核磁共振方法的优化和验证

龙舌兰糖浆因其低升糖指数和令人愉悦的口感而成为消费者喜爱的甜味剂，但用更便宜的糖浆替代它容易受到欺诈。甲¹³位点特定的C天然同位素分馏（SNIF）-NMR方法已被开发以允许C的检测₄龙舌兰产品中的植物（甘蔗、玉米），缺点是 NMR 采集时间长。在这项工作中，实现了 INEPT（通过极化转移增强的不敏感核）脉冲序列以显着减少采集时间，同时获得准确和可重复的结果。表观特定位点同位素偏差与单脉冲方法获得的值相关。分析方法按照规范程序 NF V03-110 进行验证，从样品制备到数据校正。以单脉冲法作为参考，性能至少同样好，测量时间减半，为通过核磁共振监测乙醇分子中碳的同位素比开辟了新的方法学途径，也适用于发酵和可发酵饮料。同时，