An LCEC method for the analysis of synthetic amino acids in fruit juices

Summary A fast and simple HPLC-method for the determination of synthetic amino acids in adulterated orange juice has been developed. The amino acid enantiomers were derivatized with a chiral reagent and the derivatives separated on a 3 m particle size C₁₈ column. An electrochemical detector operating in the oxidative mode was used for detection. The potential at which the derivatives are oxidized was determined by cyclic voltammetry.By using selective (electrochemical) detection it is possible to reduce the sample clean-up to simple centrifugation and filtration steps.     

酸枣果肉中挥发性化学成分的提取及分析

报道了用蒸馏-萃取法和同时蒸馏-萃取法提取酸枣果肉中挥发性物质,测得两种方法提取的酸枣果肉挥发油含量分别为1．80％和2．30％。用GC／MS法从酸枣果肉挥发油中分别分离并确定出43种和28种化学成分,分别占酸枣果肉挥发油总检出量的95．62％和94．88％。用峰面积归一化法通过化学工作站数据处理系统,得出各化学成分在挥发油中的相对百分含量。     

测定粮食、水果、蔬菜稀土总量的

以一定比例的镧、铈、镨、钕、钐的氧化物配制的混合标准溶液在酸性条件下与二溴羧基偶氮胂反应,632nm处的吸光光度在0－1．5mg/L范围内符合比耳珲律,检出限为1．5μg/L,相关系数为0．9995。方法不需加掩蔽剂。试样实测结果的相对标准偏差＜7％（n＝5）,加标回收率在84％－108％之间。     

高效液相色谱法测定果酸

本文研究了反相高效液相色谱法同时分离和测定6种果酸的色谱条件,提出了有效提取果酸的方法,并对苹果梨、香水梨等样品进行了实际分析。结果表明,该法简更快速,具有较高的准确度和精密度。     

微波场协同提取红龙果食用红色素的研究

研究了应用微波从红龙果（Hylocereus Costaricensis or Weber Britt）中提取食用红色素的新工艺，并确定了最佳工艺条件：提取剂为50％的乙醇溶液，原料用量（g）与提取剂用量（mL）比为1：90。微波功率为700W，提取时间为20s，提取次数为4次。最佳工艺条件下的色素提取率为98．94％，产品pH值为6。与溶剂浸提法相比，微波法提取红龙果食用红色素的每次提取时间由2h减少到20s，提取率从90．96％增加到98．94％。     

Determination of the carbon-13 content of sugars and pulp from fruit juices by isotope-ratio mass spectrometry (internal reference method). A European interlaboratory comparison

An interlaboratory comparison by ¹³C-isotope ratio mass spectrometry was organised by working group No. 1 of the European Commission of Standardisation (CEN/TC 174) in order to define the repeatability (r) and the reproducibility (R) of the ¹³C determination in sugars and pulp, isolated from the same fruit juice. Six unlabelled juices were analysed in 19 laboratories in the European Union, Australia and the USA. Three samples were authentic juices (orange, grapefruit, pineapple) and the remaining samples were the same juices with an addition of sugar at 15 g l⁻¹ (orange, pineapple) or 11.8 g l⁻¹ (grapefruit). The sugar was prepared by mixing equal amounts of beet and cane sucroses. The different laboratories used the same experimental protocol under different conditions (operator, conversion system for CO₂ preparation, mass spectrometer). The results for the sugars (r = 0.27%., R = 0.82%.) were comparable to those from an earlier ring test (r = 0.30%., R = 0.70%.), while the results for the pulp presented higher interlaboratory variability (r = 0.38%., R = 1.89%.) possibly due to experimental difficulties. Nevertheless, the RSD_R for free sugars ranged 0.9–3.2% and for pulp, 0.9–9.3%. On the basis of the Horwitz equation and taking account of the concentration of the isotopes measured, an RSD_R of 7–8% might have been expected. The experimentally determined RSD_R values were less than twice the theoretically expected values, which is a criterion of an acceptable method. The results were therefore considered to be acceptable by specialists in the field of isotopic analysis, and the method applied was found to improve the sensitivity of the ¹³C determination for the detection of sugar addition in fruit juices.     

Cu- and S- @SnO2 nanoparticles loaded on activated carbon for efficient ultrasound assisted dispersive µSPE-spectrophotometric detection of quercetin in Nasturtium officinale extract and fruit juice samples: CCD-RSM design

A simple, rapid, and efficient method of dispersive micro solid phase extraction (D-μ-SPE) combined with UV–Vis spectrophotometry via ultrasound-assisted (UA) was applied for the determination and preconcentration of quercetin in extract of watercress (Nasturtium officinale), fruit juice and water samples. The sorbent in this method was synthesized by doping copper and sulfide into the tetragonal structure of SnO₂-nanoparticles (Cu- and S- @SnO₂-NPs) and subsequently loading it on activated carbon (AC). The D-μ-SPE parameters with direct effect on the extraction efficiency of the targeted analyte, such as sample pH, volume of eluent, sorbent mass and ultrasound time were optimized using central composite design method. Under optimized conditions, the calibration graph for quercetin was linear in the range of 20–4000 ng mL⁻¹; the limit of detection and quantitation were 4.35 and 14.97 ng mL⁻¹, respectively and the enrichment factor was 95.24. Application of this method to analyze spiked extract, fruit juice and water samples resulted in acceptable recovery values ranging from 90.3% to 97.28% with intra-day and inter-day relative standard deviation values lower than 6.0% in all cases. Among the equilibrium isotherms tested, Langmuir was found to be the best fitted model with maximum sorption capacity of 39.37 mg g⁻¹, suggesting a homogeneous mode of sorption for quercetin.     

Miniaturized Method Based on Matrix Solid-Phase Dispersion for the Rapid Screening of 36 Pesticides in Agricultural Food Commodities

Matrix solid-phase dispersion and gas chromatography-mass spectrometry were used for the rapid screening of 36 pesticides in agricultural products. Homogenized sample (0.5 g), C₈-modified silica (0.5 g) and Na₂SO₄ (1 g) were mixed and transferred to a cartridge containing activated silica (0.5 g). Best recoveries (>60%) were found using dichloromethane-ethyl acetate (4:1) for elution. Analytical characteristics at spiking levels (10–100 μg/kg) were calculated for each pesticide. Matrix effects were studied by comparing the slopes of the matrix-matched calibration curves. Fruit and vegetable samples from South Africa complied with EU and South African current regulation, except for cypermethrin in green beans.     

The growth of giant pumpkins: How extreme weight influences shape

Great morphological differences exist among fruits and vegetables. In this combined experimental and theoretical study, we predict pumpkin shape evolution and maximum size based on their material properties. Using time-lapse photography and measurements collected by volunteer farmers, we show that as pumpkins grow, they morph from spherical to pancake shapes, flattening up to 50% in height-to-width aspect ratio. By compressing whole pumpkins in material-testing machines, we find that the elastic response of the pumpkin is insufficient to account for the large deformations characteristic of large pumpkins. We hypothesize that pumpkin flattening is caused by the weight of the pumpkin retarding its normal growth processes. We test this hypothesis using a mathematical model that assumes plant growth is stimulated in response to a tensile yield stress. We are able to predict pumpkin shapes consistent with those observed. The observed growth plasticity allows the fruit to redistribute internal stresses, thereby growing to extreme sizes without breaking.     

Ultrasound assisted extraction (UAE) of bioactive compounds from fruit and vegetable processing by-products: A review

Growing fruit and vegetable processing industries generates a huge amount of by-products in the form of seed, skin, pomace, and rind containing a substantial quantity of bioactive compounds such as polysaccharides, polyphenols, carotenoids, and dietary fiber. These processing wastes are considered to be of negligible value compared to the processed fruit or vegetable due to lack of sustainable extraction technique. Conventional extraction has certain limitations in terms of time, energy, and solvent requirements. Ultrasound assisted extraction (UAE) can extract bioactive components in very less time, at low temperature, with lesser energy and solvent requirement. UAE as a non-thermal extraction technique is better equipped to retain the functionality of the bioactive compounds. However, the variables associated with UAE such as frequency, power, duty cycle, temperature, time, solvent type, liquid-solid ratio needs to be understood and optimized for each by-product. This article provides a review of mechanism, concept, factor affecting extraction of bioactive compounds with particular focus on fruit and vegetable by-products.