Nondestructive Quantification of Foliar Chlorophyll in an Apple Orchard by Visible/Near-Infrared Reflectance Spectroscopy and Partial Least Squares

Chlorophylls respond rapidly to the current physiological status of a tree and reflect nutrient availability. Visible/near-infrared spectroscopy was attempted to determine foliar chlorophyll content in an apple orchard. Backward interval partial least squares and genetic algorithms were sequentially applied to select an optimized spectral interval and an optimized combination of spectral regions selected from informative regions in model calibration. Backward interval partial least squares was used to remove the noninformative regions, which significantly reduced the number of variables. The subsequent application of genetic algorithms-partial least squares to this reduced domain could lead to an efficient and refined model. The performance of the final model was back-evaluated according to root mean square error of calibration (RMSEC) and the correlation coefficient (R _c ) in the calibration set, and was then tested by root mean square error of prediction (RMSEP) and the correlation coefficient (R _p ) in the prediction set. The optimal backward interval partial least squares-genetic algorithms model was obtained with 5 partial least squares factors with 3 spectral regions and 71 variables selected. The measurement results of the final model were achieved as follows: RMSEC = 0.26, R _c  = 0.91 in the calibration set; and RMSEP = 0.22, R _p  = 0.91 in the prediction set. This experiment showed that visible/near-infrared spectroscopy and backward interval partial least squares-genetic algorithms are useful tools for nondestructively assessing foliar chlorophyll content and may have potential application for field assessments in decision-making and operational fertilizer management programs for apple orchards.     

超高效液相色谱-串联质谱法测定浓缩苹果汁中的熊果苷

建立浓缩苹果汁样品中熊果苷的固相萃取-超高效液相色谱-串联质谱(SPE-UPLC-MS/MS)检测方法。浓缩苹果汁样品用水溶解、过滤后,用聚苯乙烯-二乙烯基苯共聚物(PS-DVB)固相萃取柱净化,外标法定量。测定时用Eclipse Plus C18色谱柱(100 mm×2.1 mm, 1.8 μm)分离,甲醇-水系统梯度洗脱;MS测定采用多反应监测(MRM)模式。熊果苷的检出限为0.02 mg/L,在0.04～2.0 mg/L的范围内标准溶液的峰面积与质量浓度呈良好的线性关系,回收率为75.2%～102.7%,相对标准偏差(RSD)低于8.9%。该方法简便、快速、灵敏,可用于浓缩苹果汁样品中熊果苷的检测和确证。     

Use of pulsed-high hydrostatic pressure treatment to decrease patulin in apple juice

This study was aimed at reducing patulin content of apple juice using a non-thermal method, namely pulsed-high hydrostatic pressure (p-HHP). Commercially available clear apple juice was contaminated artificially with different concentrations of patulin (5, 50 and 100?ppb). Then, the samples were processed 5?min at different pressure treatments (300–500?MPa) in combination with different temperatures (30–50°C) and pulses (6 pulses?×?50?s and 2 pulses?×?150?s). To compare the impact of pulses, single pulse of high hydrostatic pressure (HHP) treatment was also applied with the same pressure/temperature combinations and holding time. Results indicated that pressure treatment in combination with mild heat and pulses reduced the levels of patulin in clear apple juice up to 62.11%. However, reduction rates did not follow a regular pattern. p-HHP was found to be more effective in low patulin concentrations, whereas HHP was more effective for high patulin concentrations. To the best of our knowledge, this is the first study using p-HHP to investigate the reduction of patulin content in apple juice.     

Determination of carbendazim and thiabendazole in apple juice by hollow fibre-based liquid phase microextraction-high performance liquid chromatography with fluorescence detection

A hollow fibre-based liquid phase microextraction (HF-LPME) coupled with high performance liquid chromatography with fluorescence detection (HPLC-FD) method was developed for the determination of carbendazim (MBC) and thiabendazole (TBZ) in apple juice. Some important extraction parameters, such as the pH of the sample solution, extraction time, stirring rate and salt concentration, were optimised. As a result, the optimal HF-LPME conditions were selected as follows: A 4?mL of sample solution (donor phase) at pH of 7.5 was used for the extraction. The pores of the hollow fibre were impregnated by 1-octanol, and 5?mM HCl (pH?=?2.5) was used as the extraction solvent. The extractions were conducted at a stirring rate of 800?rpm for 40?min. After extraction, 10?µL of the extraction solvent was injected into the HPLC system for analysis. The average enrichment factors were 106 and 114 for MBC and TBZ, respectively. A good linear relationship existed in the range of 2.5?～?500?µg?L^?1 and 5?～?500?µg?L^?1for MBC and TBZ in apple juice with the correlation coefficients (r) of 0.9995 and 0.9991, respectively. The limits of detection were 0.8?µg?L^?1 for MBC and 1.5?µg?L^?1 for TBZ (S/N?=?3?:?1). The recoveries of the method were between 86.3% and 106.0% with the relative standard deviations (RSDs) ranging from 3.3% to 8.5%. The HF-LPME-HPLC method has been successfully applied to the analysis of MBC and TBZ in apple juice, indicating that LPME-HPLC may be a promising combination for the analysis of pesticide residues for some food samples.     

液相色谱-串联质谱法测定苹果中水胺硫磷

建立苹果中水胺硫磷残留的液相色谱-串联质谱检测方法。样品以乙腈提取,采用电喷雾正离子源(ESI~+)和多重反应监测(MRM)模式测定,基质匹配标准曲线定量。结果表明:苹果基质中,水胺硫磷色谱峰面积响应值与其质量浓度呈良好线性关系(r~2=0.999),方法的线性范围为0.3~100μg/L,检出限为0.15μg/L,定量限为0.5μg/L。在5,50,100μg/kg添加水平下,水胺硫磷回收率为77.3%~95.2%,测定结果的相对标准偏差为5.7%~8.9%(n=6)。方法精密度和准确度满足残留限量监测要求。     

高效液相色谱测定浓缩苹果汁展青霉素的残留量

报道采用高效液相色谱(HPLC)法分析浓缩苹果汁中展青霉素的含量。果汁样品先经纯水稀释,再用乙酸乙酯提取,通过净化、浓缩,用甲醇/水(1∶1,V/V)定容后,进行HPLC检测。色谱柱为资生堂MG-ⅡC18柱,采用等度洗脱,流动相为甲醇、水、乙酸-乙酸钠盐缓冲液(pH=4.6);采用可变波长检测器(VWD)在276 nm波长检测。展青霉素在0.02~1.0μg/mL范围内与其峰面积呈良好的线性关系,其相关系数(R2)为0.9965。果汁样品中不同水平标准加入回收率在69.82±1.64%~87.54±3.61%范围;展青霉素在样品中残留量检测的定量限为50μg/L。     

Optimization of Ultrasound Assisted Extraction of Bioactive Compounds from Apple Pomace

In the present work, the optimization of the extraction of antioxidant compounds from apple pomace using ultrasound technology as an environmentally friendly and intensification process was developed. Different sonication powers, extraction temperatures and extraction times were studied and their influence on extraction yield and characteristics of the extracted samples (total phenolic compounds, flavonoid content and antioxidant capacity) are presented. The elaborated experimental design and the analysis of Pareto and response surface diagrams allowed us to determine the optimal extraction conditions. The conditions that allow the maximum extraction of phenolic compounds were found at 20 min, 90 °C and 50% ultrasound amplitude. Nevertheless, at these conditions, the antioxidant capacity measured by DPPH decreased in the extracted samples.     

浓缩苹果汁中多种拟除虫菊酯类农药残留量的气相色谱-质谱测定方法

采用固相萃取技术,以丙酮和正己烷提取,C18小柱净化,用GC MS可同时测定浓缩苹果汁中4种拟除虫菊酯类农药的残留量。方法的回收率在96.5%～111.9%之间,相对标准偏差为1.7%～6.9%,最低检测浓度在0.02～0.10μg kg之间。     

程序控温湿法消解石墨炉原子吸收法测定苹果中的铅

对程序控制温度、湿法消解苹果样品中铅的消解条件和石墨炉原子吸收光谱测定方法进行了研究和探讨。在本法选择的条件下,回收率为92．0％～107．0％,相对标准偏差为4．1％。经t检验及对比实验证明,与国家标准方法无显著差异。     

基于高光谱成像提取苹果糖度与硬度最佳波长

利用高光谱成像技术提取可同时检测苹果糖度与硬度的最佳波长。首先双面采集苹果的高光谱图像,获取亮度相近感兴趣区域(ROIs)的反射波形,采用二阶导数结合标准正态变量(SD+SNV)的方法平滑波形,测试ROIs的糖度与硬度;之后采用连续投影算法(SPA)提取两项指标的特征波长,根据特征波长的分布提出二次连续投影算法,结合波形集特征与两次投影结果确定不同取样面的最佳波长;最后采用遗传算法开发神经网络(GA-BP)建立预测模型,双面取样波长(543 nm和674 nm)效果最优,糖度相关系数(R)为0.847 6,均方误差(MSE)为3.32;硬度R为0.793 8,MSE为9.6。结果表明,相同波长信息可以检测苹果糖度与硬度。