高光谱成像技术结合特征提取方法的草莓可溶性固形物检测研究

采用高光谱成像技术结合不同的特征提取方法,实现了对草莓可溶性固形物含量的检测。通过提取154颗成熟无损伤草莓的高光谱图像的874～1 734 nm范围光谱信息,对941～1 612 nm光谱采用移动平均法(moving average,MA)进行预处理。基于残差法剔除19个异常样本后将剩余135个样本分为建模集(n=90)和预测集(n=45)。采用连续投影算法(successive projections algorithm, SPA),遗传偏最小二乘算法(genetic algorithm-partial least squares, GAPLS)结合连续投影算法(GAPLS-SPA),加权回归系数(weighted regression coefficient, Bw)以及CARS法(competitive adaptive reweighted sampling)选择特征波长分别提取14,17,24与25个特征波长,并采用主成分分析(principal component analysis, PCA)与小波变换(wavelet transform, WT)分别提取20与58个特征信息。分别基于全波段光谱、特征波长与特征信息建立PLS模型。所有模型都取得了较好的效果,基于全波段光谱的PLS模型与基于WT提取的特征信息的PLS模型的效果最优,建模集相关系数(r_c)与预测集相关系数(r_p)均高于0.9。结果表明高光谱成像技术结合特征提取方法可用于草莓可溶性固形物含量的检测。     

Determination of Trace Manganese by Adsorption Voltammetry

Abstract

In a solution containing 0.005M borax medium (PH= 8? 10). 0.03% ascorbic acid and 0.001% gelatin, a fine sensitive adsorptive reduction peak of manganese appeared at ?1.53v (vs.SCE) on a hanging mercury electrode by fast speed scanning voltammetry. The derivative peak current is directly proportional to the concentration of manganese in the range from 1.0×10^?8M to 2.0×10^?6M. The detection limit is 3.0×10^?9M. Using this method, we have successfuly determined tracesof Mn in water and strawberry samples.     

Changes in Volatile Aromatic Compounds of Strawberry Puree Treated by High-pressure During Storage

The changes in volatile flavor components and lipoxygenase and peroxidase enzymatic activity of Cilady strawberry puree during high pressure processing (400 MPa/20 °C/20 min) and storage at 4 °C were evaluated. High pressure processing maintains the original aromatic distribution, but after thirty days of storage an increase in some volatile compounds was observed. After high pressure treatment and storage, a residual lipoxygenase activity was observed, which could explain some slight changes of volatile compounds. On the other hand, the peroxidase was clearly inactivated by high pressure treatment.     

Capillary electrophoretic resolution of the enantiomers of 2,5-dimethyl-4-hydroxy-3(2H)-furanone, the key flavor compounds in strawberry fruit

Summary A simple capillary electrophoretic method with UV detection has been developed for resolution of the enantiomers of 2,5-dimethyl-4-hydroxy-3(2H)-furanone, the key flavor compounds in strawberry fruit. The separation was performed in fused-silica capillaries (30/40.2 cm long×50μm i.d.) with running buffer consisting of 50mm ammonium acetate, pH 4.0, containing 20mm heptakis-(2,3-O-diacetyl-6-O-sulfato)-β-cyclodextrin (HDAS-β CD). The applied potential was 10 kV, the temperature 25°C, and detection was at 280 nm. The method was used to determine the enantiomer ratio of 2,5-dimethyl-4-hydroxy-3(2H)-furanone (DMHF) isolated from strawberry fruits and from the yeastZygosaccharomyces rouxii. The formation of enantiomerically enriched(+)-DMHF byZ. rouxii was demonstrated for, the first time.     

基于高光谱图像多光谱参数的草莓成熟度识别

为了建立多光谱参数用于草莓成熟度的自动识别,采用高光谱图像技术,通过提取草莓样本ROI的平均光谱,计算已有的八个成熟度参数Ind1,Ind2,Ind3,IAD,I1,I2,I3,I4的参数值,并结合Fisher线性判别法判断八个参数对于三种成熟度(成熟、接近成熟、未成熟)草莓样本的分类识别效果,发现基于I4参数的线性判别分析模型的识别效果最佳,建模集和预测集识别准确率分别为90%和91.67%;基于草莓样本的光谱特征,提取与草莓成熟度相关的三个波长535,675和980 nm,并基于这三个波长和已有的参数形式,构建了四个用于草莓成熟度检测的新参数：i1,i2,i3,i4,通过Fisher线性判别法判断四个参数的分类识别效果,发现基于参数i1,i2和i4的线性判别分析模型的识别效果均比参数I4好,建模集和预测集识别准确率为95.83%,95.83%,95.83%和95%,95%,96.67%。结果表明新建立的多光谱参数i1,i2和i4可以用于草莓成熟度的自动分类识别,为草莓成熟度的在线检测提供了理论依据。     

Study of the structure and binding site features of FaEXPA2, an α-expansin protein involved in strawberry fruit softening

Tissue softening accompanies the ripening of many fruits and initiates the processes of irreversible deterioration. Expansins are plant cell wall proteins that have been proposed to disrupt hydrogen bonds within the cell wall polymer matrix. Several authors have shown that FaEXPA2 is a key gene that shows an increased expression level during ripening and softening of the strawberry fruit. For this reason, FaEXPA2 is frequently used as a molecular marker of softening in strawberry fruit, and changes in its relative expression have been related to changes in fruit firmness. In this context, we previously reported that FaEXPA2 has a high accumulation rate during fruit ripening in four different strawberry cultivars; however, the molecular mechanism of FaEXPA2 or expansins in general is not yet clear. Herein, a 3D model of the FaEXPA2 protein was built by comparative modeling to understand how FaEXPA2 interacts with different cell wall components at the molecular level. First, the structure was shown to display two domains characteristic of the other expansins that were previously described. The protein-ligand interaction was evaluated by molecular dynamic (MD) simulation using four different long ligands (a cellulose fiber, two of the more important xyloglucan (XG) fibers found in strawberry (XXXG and XXFG type), and a pectin (homogalacturonic acid type)). The results showed that FaEXPA2 formed a more stable complex with cellulose than other ligands via the different residues present in the open groove surface of its two domains, while FaEXPA2 did not interact with the pectin ligand.     

Development of a potentiometric sensor for the determination of saccharin in instant tea powders, diet soft drinks and strawberry dietetic jam

The construction and the analytical evaluation of a potentiometric sensor, namely, Pt∣Hg∣Hg₂(Sac)₂∣Graphite, where Sac stands for saccharinate ion, are described. This electrode has a wide linear dynamic range between 5.0 × 10^− 7 and 1.0 × 10^− 2 mol L^− 1 with a near-Nernstian slope of − 58.1 ± 1.1 mV decade^− 1 and a detection limit of 3.9 × 10^− 7 mol L^− 1. The potentiometric response is independent of the pH of the solution in the pH range 3.0-9.0. The electrode is easily constructed at a relatively low-cost with fast response time (within 10-30 s) and can be used for a period of 10 months without significant change in its performance characteristics. The proposed sensor displayed good selectivities over a variety of other anions (carboxylates and inorganic anions). The potentiometric sensor was successfully applied to the determination of saccharin in real food samples, that is, in instant tea powders, diet soft drinks and strawberry dietetic jam.     

An RP-HPLC determination of 5-hydroxymethylfurfural in honey The case of strawberry tree honey

The use of the RP-HPLC official method of the International Honey Commission (IHC) for the determination of 5-hydroxymethylfurfural (HMF) in strawberry tree honey (Arbutus unedo, a typical Sardinian honey) has brought to light a specific and heavy chromatographic interference that prevents accurate quantification. The interference has been identified as homogentisic acid (HA), i.e. the marker of the botanical origin of the honey. For this reason, an alternative RP-HPLC method is proposed. The bias-free method allows a complete separation of HMF from HA to the baseline level and is faster and more precise than the RP-HPLC official method: the detection and quantification limits are 1.9 and 4.0 mg kg⁻¹, respectively, whereas the repeatability is ca. 2% in the HMF concentration range of 5-140 mg kg⁻¹.