近红外光谱法快速检测梨汁中柠檬酸和L-苹果酸含量

利用近红外光谱技术对梨汁中柠檬酸和L-苹果酸含量进行快速定量检测,并通过6种光谱预处理及3种数学校正方法对柠檬酸和L-苹果酸含量预测模型进行优化。本研究采用近红外光谱仪在1 100~1 650 nm光谱范围内共采集70个梨汁样本的近红外光谱图,并利用高效液相色谱法测定柠檬酸和L-苹果酸的含量。首先对样本原始光谱图经过多元散射校正(MSC)、一阶导数、二阶导数等方法进行预处理,然后通过主成分分析(PCR)、修正的最小二乘法(MPLS)及偏最小二乘法(PLS)等分别建立梨汁中柠檬酸和L-苹果酸含量的预测模型,并对该模型进行优化。优化后,柠檬酸的最佳模型为PLS结合MSC;L-苹果酸的最佳模型为MPLS结合SNV且去散射;最佳预测模型的预测相关系数最高可达0.985,预测标准差最低为0.039%,相对分析误差最大为3.46。结果表明,近红外光谱可作为一种可靠、快速、无损、简单的方法用于梨汁中柠檬酸和L-苹果酸含量的测定。该方法为生产企业及监管部门开展梨汁的掺伪鉴别提供了依据。

Rapid Determination of Citric Acid and L-malic Acid Content for Pear Juice by Near Infrared Spectroscopy

Near infrared spectroscopy (NIR) was used to detect citric acid and L-malic acid in pear juice quantitatively.The prediction models of citric acid and L-malic acid were optimized by combing 6 pretreatment methods with 3 mathematical correction components.The NIR spectra of 70 pear juice samples were collected in spectral range of 1 100~1 650 nm using an near infrared spectrometer, and the true content of citric acid and L-malic acid was measured by high performance liquid chromatography (HPLC).First, the original spectra were optimized with multiplication scatter correction (MSC), first derivative, second derivative and so on.Then, the prediction models of citric acid and L-malic acid content in pear juice were established using principal component regression (PCR), modified partial least square (MPLS), and partial least square (PLS), respectively.Finally, the prediction models were optimized and validated by eliminating outlier samples. The results indicated that the established mathematical model by MSC coupled with PLS, SNV and detrend coupled with MPLS had good predictive ability for citric acid and L-malic acid.The correlation coefficient of the best prediction model after optimized in prediction sets was 0.985, the minimum standard error of prediction (SEP) was 0.039%, and the maximum standard deviation ratio (SDR) was 3.46.The results showed that NIR spectroscopy could be used as a reliable, rapid, nondestructive and simple method to determine the content of citric acid and L-malic acid in pear juice.The effective and feasible method would help detect adulteration pear juices.