Shelf life,physicochemical, microbiological and antioxidant properties of purple cactus pear (Opuntia ficus indica) juice after thermoultrasound treatment

The objective of this study was to evaluate changes in color, betalain content, browning index, viscosity, physical stability, microbiological growth, antioxidant content and antioxidant activity of purple cactus pear juice during storage after thermoultrasonication at 80% amplitude level for 15 and 25 min in comparison with pasteurized juice. Thermoultrasound treatment for 25 min increased color stability and viscosity compared to treatment for 15 min (6.83 and 6.72 MPa, respectively), but this last parameter was significantly lower (p < 0.05) compared to the control and pasteurized juices (22.47 and 26.32 MPa, respectively). Experimental treatment reduced significantly (p < 0.05) sediment solids in juices. Total plate counts decreased from the first day of storage exhibiting values of 1.38 and 1.43 log CFU/mL, for 15 and 25 min treatment, respectively. Compared to the control, both treatments reduced enterobacteria counts (1.54 log CFU/mL), and compared to pasteurized juice decreased pectinmethylesterase activity (3.76 and 3.82 UPE/mL), maintained high values of ascorbic acid (252.05 and 257.18 mg AA/L) and antioxidant activity (by ABTS: 124.8 and 115.6 mg VCEAC/100 mL; and DPPH: 3114.2 and 2757.1 μmol TE/L). During storage thermoultrasonicated juices had a minimum increase in pectinmethylesterase activity (from day 14), and exhibited similar total plate counts to pasteurized juice. An increase of phenolic content was observed after 14 days of storage, particularly for treatment at 80%, 25 min, and an increase in antioxidant activity (ABTS, DPPH) by the end of storage.     

The disappearance rate and risk assessment of thiacloprid residues in Asian pear using liquid chromatography confirmed with tandem mass spectrometry

This study was undertaken to quantify the residue levels and propose the dissipation kinetics of thiacloprid formulated as suspension concentrate in field‐incurred Asian pears grown under two different open‐field conditions. Samples were extracted with 20% distilled water in acetonitrile; partitioned with brine water and dichloromethane; and purified with a Florisil solid phase extraction cartridge. The analyte was identified with an LC ultraviolet detector, and field‐incurred samples were confirmed using LC–MS/MS. The calibration curve was linear over the range 0.05–5.0 mg/L with a satisfactory coefficient of determination (R ² = 0.9994). The limits of detection and limits of quantification (LOQ) were 0.003 and 0.01 mg/kg, respectively. The recovery rate fortified to blank samples at LOQ, 10× LOQ, and the maximum residue limit (MRL) were between 73.7 and 86.2% with relative standard deviation ≤9.0%. The residual concentrations at both sites were considerably lower than the MRL (0.7 mg/kg) set by the Korean Ministry of Food Drug Safety, with biological half‐lives of 5.0 and 7.4 days, for sites 1 and 2, respectively. From the pre‐harvest residue limit curve, it was predicted that if the residues were <1.13 or 1.40 mg/kg 10 days before harvest, the residue level would be lower than the MRL during harvest. Risk assessment on day 0 showed an acceptable daily intake (%) of 13.0% and 11.0% for sites 1 and site 2, respectively, which indicates that the residual amounts are not hazardous to the Korean population.     

遗传算法结合偏最小二乘法无损评价西洋梨糖度

基于遗传算法的波段选择法在组合优化问题上具有很大的搜索优势,适应性很广。文章将该方法应用于西洋梨糖度近红外光谱分析中,探讨数据优化筛选的可行性。光谱经多元散射校正或标准归一化处理后进行波段选择,选择结果与样品中被测成分有关, 4个品种洋梨的最佳个体染色体编码有一定共性。分别建立了四种洋梨的GA-PLS模型和全谱模型,早红考密斯、五九香、凯斯凯德和康佛伦斯的GA-PLS建模数据点分别从1 557减少到了434,496,310和496。GA-PLS/Fr-PLS模型的预测标准偏差分别为0.428/0.518,0.696/0.694,0.425/0.421和0.567/0.633, 其中早红考密斯和康佛伦斯GA-PLS模型的预测精度明显优于全谱模型,而五九香和凯斯凯德的GA-PLS模型与全谱模型相近。结果表明,遗传算法用于PLS建立西洋梨糖度校正模型前的数据优化筛选是可行的, 有效提高测量精度, 减少建模变量。     

固相萃取-HPLC法测定浓缩梨汁中噻菌灵、多菌灵的残留量

研究了一种可同时测定浓缩梨汁中噻菌灵和多菌灵残留量的固相萃取-高效液相色谱分析方法.浓缩梨汁样品与水按一定比例稀释后,经过调pH、离心、过滤,用混合相固相萃取小柱(Mixed-mode SPE)进行提取、净化,用配有二级管阵列检测器(DAD)的液相色谱仪检测,外标法定量.使用噻菌灵和多菌灵对照品进行添加回收率测定,结果显示本方法对噻菌灵的最低检出限为0.020 mg/kg,回收率为80.5%~84.3%;对多菌灵的最低检出限为0.020 mg/kg,回收率为83.2%~92.5%;测定的相对标准偏差均不大于5%.本方法简单、快速、准确,能满足常规噻菌灵和多菌灵残留量检测的需要.     

Prickly Pear Seed Oil Extraction,Chemical Characterization and Potential Health Benefits

Prickly pear (Opuntia ficus-indica L.) is a member of the Cactaceae family originally grown in South America, and the plant is now distributed to many parts of the world, including the Middle East. The chemical composition and biological activities of different parts of prickly pear, including cladodes, flowers, fruit, seeds and seed oil, were previously investigated. Oil from the seeds has been known for its nutritive value and can be potentially used for health promotion. This review is an effort to cover what is actually known to date about the prickly pear seeds oil extraction, characteristics, chemical composition and potential health benefits to provide inspiration for the need of further investigation and future research. Prickly pear seeds oil has been extracted using different extraction techniques from conventional to advanced. Chemical characterization of the oil has been sufficiently studied, and it is sufficiently understood that the oil is a high linoleic oil. Its composition is influenced by the variety and environment and also by the method of extraction. The health benefits of the prickly pear seed oil were reported by many researchers. For future research, additional studies are warranted on mechanisms of action of the reported biological activities to develop nutraceutical products for the prevention of various chronic human diseases.     

Various extraction methods for detection of bistrifluron residues in Asian pear using high‐performance liquid chromatography: application to dissipation patterns under open‐field conditions

The present study was carried out to develop an analytical method for the detection and quantification of bistrifluron, a benzoylphenylurea compound, in pear using high‐performance liquid chromatography with UV detection. Samples were extracted using conventional, AOAC and EN quick, easy, cheap, effective, rugged and safe ‘QuEChERS’ methods. As expected, conventional and EN‐QuEChERS methods gave higher recoveries than AOAC. In addition, interference around the analyte retention time was observed in the conventional method. Thus, the EN‐QuEChERS method was selected and validated by studying various parameters, including linearity, limit of detection, limit of quantification (LOQ), recovery and precision. Linearity was excellent, with a correlation coefficient of 0.9998. Recovery rates at three spiking levels (0.05, 0.2 and 1 mg/kg) ranged from 73.76 to 98.66%. Intra‐ and inter‐day precisions, expressed as relative standard deviations, were <6%. The LOQ of 0.05 mg/kg was considerably lower than the maximum residue limit (1 mg/kg) set by the Korean Ministry of Food and Drug Safety. The developed method was successfully applied to open‐field pear samples, in which the target analyte was slowly dissipated (55% decline) over 14 days with a half‐life of 10.19 days. Notably, the residue levels throughout the period of sample collection (14 days) were lower than the maximum residue limit, indicating that the residue was not hazardous for consumers. Copyright © 2016 John Wiley & Sons, Ltd.     

SFC-UV determination of diflubenzuron residues,teflubenzuron and triflumuron in apple and pear pulps for baby food

Summary A method to determine residues of diflubenzuron (DFB), teflubenzuron (TFB), triflumuron (TFM) at 0.01 ppm with recoveries above 60% in apple and pear pulps for baby food is described. DFB, TFB and TFM are extracted with methanol, and cleaned up by SPE using C18 stationary phase and methanol mobile phase. Analysis of the three pesticides is by SFC-UV at 254 nm using a Diol column, and CO₂ at 30 MPa and 40°C modified with acetonitrile (10%) mobile phase.     

Sensory Quality Evaluation of Korla Pear from Different Orchards and Analysis of Their Primary and Volatile Metabolites

Metabolites play vital roles in shaping the quality of fresh fruit. In this study, Korla pear fruit harvested from twelve orchards in South Xinjiang, China, were ranked in sensory quality by fuzzy logic sensory evaluation for two consecutive seasons. Then, gas chromatography-mass spectrometry (GC-MS) was applied to determine the primary metabolites and volatile compounds. Sensory evaluation results showed that the panelists were more concerned about ‘mouth feel’ and ‘aroma’ than about ‘fruit size’, ‘fruit shape’ and ‘peel color’. In total, 20 primary metabolites and 100 volatiles were detected in the pear fruit. Hexanal, (E)-2-hexenal, nonanal, d-limonene, (Z)-3-hexen-1-yl acetate and hexyl acetate were identified as the major volatile compounds. Correlation analysis revealed that l-(+)-tartaric acid, hexanoic acid, trans-limonene oxide and 2,2,4-trimethyl-1,3-pentanediol diisobutyrate were negatively correlated with sensory scores. Furthermore, OPLS-DA results indicated that the fruit from three orchards with lower ranks in quality could be distinguished from other samples based on the contents of l-(+)-tartaric acid and other eight metabolites, which were all associated with ‘mouth feel’ and ‘aroma’. This study reveals the metabolites that might be closely associated with the sensory quality attributes of Korla pear, which may provide some clues for promoting the fruit quality in actual production.     

基于变量优选和快速独立成分分析的黄花梨可溶性固形物可见/近红外光谱检测

为建立预测能力高、稳定性强的可见/近红外漫透射光谱无损检测黄花梨可溶性固形物(SSC)数学模型,对比各种预处理方法、变量优选方法、快速独立主成分分析(FICA)以及最小二乘支持向量机(LS-SVM)对黄花梨SSC模型的影响,得出最佳的组合方法用于建立黄花梨可溶性固形物(SSC)预测模型。采用Quality Spec型光谱仪采集550~950 nm波段范围内的黄花梨漫透射光谱并采用遗传算法、连续投影算法和CARS(competitive adaptive reweighted sampling)三种方法筛选黄花梨可溶性固形物的光谱特征变量,再结合FICA提取光谱主成分,最后采用LS-SVM建立黄花梨的SSC预测模型。结果显示,采用CARS筛选的21个变量,经FICA挑选出12个主成分数,联合LS-SVM所建立的CARS-FICA-LS-SVM黄花梨SSC预测模型性能最佳,建模集和预测集的决定系数及均方根误差分别为0.974,0.116%和0.918,0.158%,同直接采用PLS方法建模相比,变量数从401个下降到21,主成分数由14下降到12,建模集和预测集决定系数分别上升了0.023,0.019,而建模和预测均方根误差分别下降了0.042%和0.010%。CARS-FICA-LS-SVM建立黄花梨SSC预测模型能够有效地简化预测模型并提高预测模型精度。     

Infrared Spectroscopy and Morphological Assessments on the Nutritional Value of Prickly Pear Fruit

The prickly pear fruit helps in combating viral based infections. It is used to treat diabetes and declared to possess hypoglycemic effects. There is also record of the usage of the fruit in the olden days as a remedy for diabetes, lipid disorders, inflammation, ulcers, and pharmacologic side effects. The chemical composition and nutritional values of skin, flesh and seed of prickly pear fruit were investigated and discussed on a dry weight situation. The infrared spectra as well as scanning electron microscopy (SEM) techniques were used to identify the functional groups of carbohydrates, amino acids, and protein. The infrared spectral data of all three (skin, flesh, and seeds) species were recorded and assigned to the presence of distinguish peaks that referred to the three different sugars (glucose, fructose and saccharose) and cyclic aliphatic hydrocarbons moieties. On the other hand, the SEM is a powerful tool to investigate the morphological features of the components. SEM assays were examined on the surfaces of skin, flesh and seed branches showing a small particle that tends to form clusters with different shapes compared to each other. The Energy-dispersive X-ray spectroscopy (EDX) is an analytical technique used for the elemental analysis or chemical characterization of a sample. The EDX spectral technique of the skin, flesh and seeds were confirmed the presence of different essential and useful elements such as carbon, oxygen, magnesium, calcium, potassium, sulfur, aluminum, silicon, chloride, and phosphorus.