Abstract：Visible and near infrared reflectance spectroscopy (Vis/NIRS) as a new method was proposed for the rapid and non-destructive measurement of citric acids in orange juice. High performance liquid chromatography (HPLC) was used as a reference method for the spectral analysis of citric acids. The original spectral data were preprocessed by the smoothing method with five smoothing points in order to eliminate the noise. Before modeling, large spectral data were compressed by wavelet transform (WT) in Matlab7.01 with the edited program to reduce the dimensions and modeling time, and then the new variables after being compressed were used to build PLS calibration in spectral software Unscrambler 9.5. Considering the effect of different wavelet functions and decomposed scales on the data compressed, the optimal wavelet function Db4 and decomposed scale 5 were determined by predictive residual error sum of squares (PRESS). A total of forty samples were used in our experiment, including thirty samples for the calibration model and ten unknown samples for the prediction. The quality of the calibration model was evaluated by the correlation coefficients (r) and standard error of calibration (SEC), and the prediction results were assessed by correlation coefficients (r) and standard error of prediction (SEP). Comparing WT-PLS model with PLS model, the result of WT-PLS model was r of 0.901 and SEP of 0.937, while the result of PLS model was r of 0.849 and SEP of 1.662, indicating that the prediction result from PLS model with wavelet transform was better than that from PLS model.
Key words：Vis/NIRS;Partial least squares;Wavelet transform;Orange juice;Citric acid
岑海燕,何勇,张辉,冯凤琴*. 可见光/近红外光谱技术快速测定橙汁柠檬酸含量[J]. 光谱学与光谱分析, 2007, 27(09): 1747-1750.
CEN Hai-yan, HE Yong, ZHANG Hui, FENG Feng-qin*. Rapid Measurement of Citric Acids in Orange Juice Using Visible and Near Infrared Reflectance Spectroscopy. SPECTROSCOPY AND SPECTRAL ANALYSIS, 2007, 27(09): 1747-1750.
[1] HAN Ya-shan, CUI Yu-lin(韩雅珊，崔雨林). Acta Nutrimenta Sinica(营养学报), 1996, 18(1): 120. [2] Fish W W, Perkins-Veazie P, Collins J K. J. Food Composition Anal., 2002, 15(3): 309. [3] Breithaupt D E. Food Chemistry, 2004, 86(3): 449. [4] HE Yong, FENG Shui-juan, DENG Xun-fei, et al. Food Research International, 2006, 39(6): 645. [5] ZHAO Chen, QU Hai-bin, CHENG Yi-yu(赵 琛，瞿海斌，程翼宇). Spectroscopy and Spectral Analysis(光谱学与光谱分析),2004,24(1): 50. [6] HE Yong, FENG Shui-juan, LI Xiao-li(何 勇，冯水娟，李晓丽). Spectroscopy and Spectral Analysis(光谱学与光谱分析), 2006, 26(11): 2021. [7] Ann P, Nico S, Kathleen T, et al. Biosystems Engineering, 2002, 81(3): 305. [8] HE Yong, LI Xiao-li(何 勇，李晓丽). J. Infrared Millim Waves(红外与毫米波学报), 2006，25: 192. [9] Mehi P M, Chen Y R, Kim M S, et al. Journal of Food Engineering, 2004, 61(1): 67. [10] HE Yong, LI Xiao-li, SHAO Yong-ni(何 勇，李晓丽，邵咏妮). Spectroscopy and Spectral Analysis(光谱学与光谱分析)，2006,26(5): 850. [11] TANG Yan-feng, ZHANG Zhuo-yong, FAN Guo-qiang(汤彦丰，张卓勇，范国强). Spectroscopy and Spectral Analysis(光谱学与光谱分析), 2005, 25(4): 521. [12] YAN Shou-he(阎守和).Shanghai Tea Industry(上海茶叶)，2005，3：19. [13] WANG Qing-ping, DONG Bao-sheng(汪庆平，董宝生).Yunnan Agricultural Science and Technology(云南农业科技), 2003, 6: 11. [14] LI Ning, MIN Shun-geng, QIN Fang-li, et al(李 宁，闵顺耕，覃方丽，等). Spectroscopy and Spectral Analysis(光谱学与光谱分析),2004,24(1):45. [15] Watanabe S H K, Iwamoto M J. Japanese Soc.Hort.Sci., 1992, 61(2): 445. [16] JIANG Tao, XIAO Chen(江 涛，晓 晨). Laser & Optronics Progress(激光与光电子学进展), 2000,(8): 52. [17] WU Jun, BAI Qi-lin, SU Sheng-bao, et al(吴 军，白琪林，苏胜宝，等). Chinese Journal of Analytical Chemistry(分析化学)，2005，33(10)：1421. [18] Shao X G, Leung A K, Chau F T. Account Chem. Res., 2003, 36(4): 276.
