基于LF-2D-NMR的文冠果含水含油率检测方法

    Detection of the moisture and oil contents of Xanthoceras sorbifolia Bunge using LF-2D-NMR

    • 摘要: 文冠果的含水、含油率的高低影响其育种及加工储藏结果。为探求一种无损、快速、准确的文冠果含水含油率检测方法,该研究分别采用干取样法结合低场核磁共振技术(low field nuclear magnetic resonance,LF-NMR)、低场二维核磁共振技术(low field two-dimensional nuclear magnetic resonance,LF-2D-NMR)两种试验方式进行数据采集。通过系列试验确定两种技术在检测文冠果含水含油率的可行性。结果表明:与国标法测试结果相比,LF-NMR结合干取样法采集获取的数据异常,并且由于LF-NMR无法区分重叠峰信号,无法解释产生异常变化的原因,故该方法不适用于文冠果含油含水率的检测;LF-2D-NMR能够定性分析一维波谱中信号重叠无法区分组分的问题,成功解释了干取样法结合LF-NMR数据异常的原因。同时,LF-2D-NMR测得的文冠果T1-T2谱峰面积与烘箱干燥法及索氏提取法获取的水油含量之间存在显著的线性相关性,经与真值验证过后的决定系数R2分别为0.920 9和0.942 4,可以用于文冠果含水含油率的定量分析。该研究拓展了低场核磁共振技术的理论认知深度,提高检测精度及在实际生产中的指导价值。

       

      Abstract: Moisture and oil content of Xanthoceras sorbifolia Bunge can dominate its breeding, processing, and storage in fruit production. This study aims to explore a non-destructive, rapid, and accurate detection of the moisture and oil content of Xanthoceras sorbifolia Bunge, providing excellent seeds during oil extraction and breeding. The peak overlapping was found during detection using low-field nuclear magnetic resonance (LF-NMR). Two ways were then selected to validate the overlapping moisture and oil signals in food products. One was the removal of the water signal using LF-NMR with dry sampling. The water was evaporated to eliminate the overlapping area and then measure the oil content. Another was to separate the oil and moisture signals using low-field two-dimensional nuclear magnetic resonance (LF-2D-NMR). A series of experiments were conducted to verify the feasibility of two techniques. The national standard oven drying was used to detect the moisture, while Soxhlet extraction was used to detect the oil. The benchmark values were then obtained to verify the accuracy of nondestructive testing. The test results show that anomalous data was using LF-NMR with dry sampling, compared with the national standard. Matlab platform was used to extract the eigenvalues from each color of the Lab in the MRI pseudo-color map. The collected signals were shifted from outside to inside during drying. The physicochemical test revealed that there were abnormal changes inside the Xanthoceras sorbifolia Bunge. Since LF-NMR failed to differentiate and quantify the overlapping NMR signals in the samples, dry sampling was used to consider the anomalous variations behind these signals. As such, LF-2D-NMR was better performed to detect the oil and moisture content of Xanthoceras sorbifolia Bunge, particularly for the overlapping signals in the one-dimensional spectra. It was found that the drying induced the molecular rupture in the internal molecules of Xanthoceras sorbifolia Bunge, leading to the increasing values of saturated fatty acid and carbonyl. The hazardous substances were formed to explain the abnormal peaks in the LF-NMR data. Meanwhile, there was a significant linear correlation between the peak areas of the T1-T2 spectra of Xanthoceras sorbifolia Bunge that was measured by LF-2D-NMR. The moisture and oil contents were obtained after oven drying and Soxhlet extraction. The correlation coefficients of R2 after verification were 0.920 9 and 0.942 4, respectively. Therefore, the LF-2D-NMR technique can be expected to quantitatively analyze the moisture and oil contents of Xanthoceras sorbifolia Bunge. This finding can provide the theoretical reference of the LF-NMR technique for the high detection accuracy in practical production.

       

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