Experimental design applied to the analysis of volatile compounds in apple juice by headspace solid-phase microextraction

A simple and fast method based on solid-phase microextraction (SPME) followed by fast gas chromatography (Fast GC) has been developed for the analysis of volatile compounds in Asturian apple juices employed in the cider production. Three different fiber coatings have been checked (PDMS, PDMS-DVB and CAR-PDMS) and PDMS-DVB has been presented to be the most suitable one. Experimental design has been employed in the optimization of extraction factors and robustness assessment. The use of Fast GC allowed the separation of 14 compounds (esters, aldehydes and alcohols) in approximately 4 min, clearly reducing the analysis time when compared to conventional GC. Good linearity, recoveries and repeatability of the solid-phase microextraction were obtained with r(2) values, recoveries and relative standard deviations ranging from 0.9822 to 0.9998, 83.2 to 109.8% and 0.5 to 11.7%, respectively, using standard solution.     

A novel method for the determination of total 1,3-octanediols in apple juice via 1,3-dioxanes by solid-phase microextraction and high-speed gas chromatography

In this work, a novel, simple and fast method based on solid-phase microextraction (SPME) followed by high-speed gas chromatography (HSGC) was developed for the analysis of total 1,3-octanediols in apple juices by means of derivatization reaction to volatile 1,3-dioxanes. The derivatization reaction, SPME conditions, glycosidically bound fraction and 1,3-nonanediol as a surrogate standard were studied. The formation of 1,3-dioxanes from 1,3-diols was confirmed by GC–MS. The method was validated obtaining a regression coefficient (r²) of 0.9996, precisions between 0.3 and 9.8%, extraction recoveries in the range 94.7–112.2% and LOD of 2.9 μg l⁻¹. Experimental design has been employed in the optimization of extraction factors and robustness assessment. The method was applied to the analysis of 21 Asturian apple varieties finding a double reciprocal relationship between the concentrations of saturated and unsaturated 1,3-octanediol.     

均值+方差二维表征高光谱信息的苹果腐败预警方法

为实现苹果在贮藏过程中有效的腐败预警,提出一种基于高光谱图像灰度值均值融合方差的二维高光谱信息表征方法,并构建了苹果样本的巴氏距离（BD）预警模型。首先,为获得有效的光谱信息,对高光谱图像的感兴趣区域（ROI）进行了选择;同时,为减少噪声影响,通过对比分析6种光谱信息的预处理方法,最终采用Savitzky-Golary(SG)平滑方法,分别对均值和方差表征的两种光谱信息进行全波段（371.05～1 023.82 nm）光谱曲线降噪处理。其次,为获得特征波长,从降噪后的光谱曲线中运用连续投影算法（SPA）结合样本色调角和失水率2个理化指标,提取了高光谱图像共同的特征波长,分别得到了两种表征方式下的7个（均值表征）和8个（方差表征）特征波长。然后,通过分析样本色调角随贮藏天数变化的折线图,确定了图中发生明显转折的数据点所对应的贮藏日期,并结合样本贮藏期间实际观察的情况,初步界定第21贮藏日为样本腐败的基准日。另外,依据苹果样本表皮叶绿素特征吸收波长（675 nm左右）,绘制出平均光谱反射值变化趋势图,发现趋势图在第21日升至最高点,吻合色调角的分析结果,这表明样本确实从第21日开始腐败。因此,第21贮藏日对应的特征波长可用来建立腐败基准日的光谱信息表征向量。最后,分别建立基于均值表征、方差表征及二者相融合表征下的光谱信息巴氏距离腐败预警模型。结果表明：基于均值融合方差的光谱表征信息所建立的预警模型相较于它们各自建立的预警模型,波动性进一步减弱,可更好地反映苹果样本在贮藏过程中接近腐败的程度。因此,融合灰度值均值和方差的光谱表征信息更能全面的表征苹果贮藏过程中的品质变化,模型预警的稳健性及泛化能力更强,为利用高光谱图像信息对苹果贮藏进行腐败预警提供了新思路。     

分数阶微分预处理及PCA-SRDA的多模型融合对红富士苹果产地溯源

苹果产地溯源具有重要的应用价值和现实意义。为了探寻苹果产地溯源新方法,以红富士品种为研究对象,以新疆阿克苏、山东烟台、陕西洛川三个产地671个红富士苹果样本为试材,分别采集其590～1 250 nm的近红外透射光谱,然后基于分数阶微分(FD)及主成分分析(PCA)-谱回归判别分析(SRDA)进行多模型融合,构建红富士苹果产地溯源的集成学习模型。首先,将经过光谱校正后的光谱数据划分为训练集和测试集,并利用分数阶微分预处理训练集光谱,获取不同阶次(取0～2阶,步长为0.1)的分数阶微分光谱;结合不同阶次的分数阶微分光谱及PCA-SRDA算法构建基学习器,将基学习器预测结果构成一个新训练集,并通过决策树算法完成模型融合,得到最终分类预测模型;随后,采用对应阶次的分数阶微分预处理测试集光谱,并基于已建立的基学习器,获得测试集相应的预测结果;最后,将预测结果构成一个新测试集,并基于已建立的分类预测模型,输出最终的预测结果。按7∶3比例随机划分样本集,并进行200次重复实验。结果表明,结合不同阶次的分数阶微分预处理及线性判别分析(LDA)、 SRDA、 PCA-LDA、 PCA-SRDA算法建立多...     

Intensity based algorithms for biospeckle analysis

In this paper, two algorithms, one is an Alternative Fujii method and other is parameterized form of temporal difference (PTD) method are presented. Experimental results for both the methods using sequential biospeckle images of fresh apple have been presented and compared with the results obtained using that of Generalized Difference (GD) and Parameterized Fujii. Good agreements are seen for particular values of parameters.     

便携式近红外光谱仪测定苹果酸度和抗坏血酸的研究

应用便携式近红外光谱分析仪对6种苹果进行无损检测,运用Kernel Isomap结合广义回归神经网络的方法分别建立苹果酸度和抗坏血酸定量分析模型.结果表明:采用Kernel Isomap方法能够使模型具有良好的预测能力.苹果酸度模型校正集相关系数Rc=0.9994,预测集相关系数Rp=0.979 9,RMSEP=0.0...     

Determination of the Volatile Components of Apple Juice Using Solid Phase Microextraction and Gas Chromatography–Mass Spectrometry

Headspace solid phase microextraction and gas chromatography–mass spectrometry were employed to characterize the volatile organic compounds, responsible for the flavor, in apple juice. The method was applied for commercial and fresh juice. More than seventy volatile organic compounds were determined from different chemical families. The characterization was based on the relative quantities of total terpenes, sesquiterpenes, esters, ketones, and alcohols. A new index was proposed for apple juice assessment and quality evaluation, based on the relative ratios of total sesquiterpenes and total terpenes.     

Stereoselective synthesis of 10,14-dimethyloctadec-1-ene, 5,9-dimethyloctadecane, and 5,9-dimethylheptadecane, the sex pheromones of female apple leafminer

The stereoselective synthesis of (10R,14R)-10,14-dimethyloctadec-1-ene (1), (5R,9R)-5,9-dimethyloctadecane (2), and (5R,9R)-5,9-dimethylheptadecane (3) the sex pheromone components of female apple leafminer was accomplished by reductive elimination tosyl and isonitrile groups of dialkylated tosylmethyl isonitrile. The key steps involved were dialkylation of TosMIC with 1-iodo 2-methyl alkanes, which were derived from Evan's alkylation of chiral auxiliary and subsequent reduction.     

Separation and identification of polyphenols in apple pomace by high-speed counter-current chromatography and high-performance liquid chromatography coupled with mass spectrometry

Apple pomace, a by-product in the processing of apple juice, was investigated as a potential source of polyphenols. Two methods of separation and purification of polyphenols from apple pomace extract were established by combination of gel chromatography with high-speed counter-current chromatography (HSCCC) and solvent extraction with HSCCC, respectively. The optimal separation was performed on a Sephadex LH-20 column using gradient aqueous ethanol as eluting solvent from 0% to 100% in increments of 10%. HPLC analysis indicated that main polyphenols existed in fractions eluted between 40% and 50% aqueous ethanol. The fractions of interest from column were separated by HSCCC with the solvent system hexane–ethyl acetate–1% aqueous acetic acid (0.5:9.5:10, v/v/v). Ethyl acetate fractionation of the apple pomace extract followed by direct HSCCC separation by the same solvent system in the volume ratio of 1:9:10 also produced a good separation of the main polyphenols of interest. Six high-purity polyphenols were achieved tentatively and identified by HPLC/MS: chlorogenic acid (1, m/z 354), quercetin-3-glucoside/quercetin-3-glacaside (2, m/z 464), quercetin-3-xyloside (3, m/z 434), phloridzin (4, m/z 436), quercetin-3-arabinoside (5, m/z 434), and quercetin-3-rhamnoside (6, m/z 448). These results provided a preliminary foundation for further development and exploration of apple pomace.     

高效液相色谱法测定苹果汁中8种酚类化合物

提出了高效液相色谱法同时测定苹果汁中儿茶素、绿原酸、咖啡酸、表儿茶素、香豆酸、阿魏酸、槲皮素和根皮素等8种酚类化合物的方法,并考察了光照、保存时间等因素对酚类化合物的稳定性的影响.选用Eclipse XDB C18色谱柱(150 mm×4.6mm,5μm),以甲醇和乙酸-水(1+99)溶液作为流动相进行梯度洗脱,利用二极管阵列检测器,在各种酚类物质的最大吸收波长下进行紫外光度检测.对各化合物工作曲线的线性范围作了试验,并推导得到相应的线性回归方程,其相关系数均为0.999 9,在苹果汁样品的基础上用标准加入法各进行7次测定,测得平均回收率均在96.0%～100.8%之间,相对标准偏差(n=7)小于等于3.0%,8种化合物的检出限(3S/N)分别为20,10,4,20,5,8,30和7μg·L-1.