Controlled atmosphere storage of deciduous fruit in South Africa

The quality of apples and pears can be greatly improved by applying controlled atmosphere (CA) conditions of 1–2% oxygen. Fast precooling and storage at −0.5°C in addition to rapid application of CA conditions also improve the storage life and eating quality of apples and pears. CA storage of Flamekist nectarines and Santa Rosa plums, is not considered practical or economical due to the poor texture (mealiness) and breakdown which result. Experimental data are presented to quantify these effects.     

Development of electronic nose method for evaluation of residual solvents in low‐density polyethylene films

Flexible packaging films containing high levels of residual volatile organic compounds (VOCs) can alter the flavour and odour of packaged foods. Currently, a range of gas chromatographic techniques and sensory evaluations are used for assessing the residual VOCs in packaging films. An objective method for assessing the residual solvents from low‐density polyethylene (LDPE) was developed using an Alpha MOS Fox 3000 electronic nose (e‐nose) equipped with 12 metal oxide semiconductor sensors. Three VOCs, ethyl acetate, ethyl alcohol and toluene, were chosen as models for solvents of interest in flexible food packaging analysis. LDPE film samples were spiked with single and binary mixtures of solvents and analysed using the e‐nose and by GC–FID (HP 6890; Hewlett‐Packard Co., Wilmington, DE). The responses obtained from the e‐nose were processed using principal component analysis (PCA) and discriminate factorial analysis (DFA) in order to identify the residual solvents. Partial least squares analysis (PLS) was also used to quantify the amount of residual solvent and to correlate the e‐nose results with gas chromatography, which is currently the standard method for determining residual VOCs in packaging films. There was good agreement between the e‐nose responses and gas chromatography results for single solvents (r = 0.90–0.98). The technique also worked for binary solvent mixtures (r = 0.84–0.99). The electronic nose can be a viable alternative to traditional techniques while providing simplicity and objectivity, which would be extremely advantageous in routine quality control of residual solvents. Copyright © 2006 John Wiley & Sons, Ltd.     

Development of electronic nose method for evaluation of HDPE flavour characteristics,correlated with organoleptic testing

A method for analysing food‐grade high‐density polyethylene (HDPE) resins was developed using the electronic nose (E‐nose) system. Eight different HDPE resin grades were analysed using the E‐nose. The E‐nose system with principal component analysis was found to be capable of discriminating between the resin grades. The resin samples were soaked in ultra‐pure water at 40 ±2°C for 1 week. Water samples stored in contact with the resins were organoleptically evaluated at different concentrations by untrained discrimination sensory panels and the resins were ranked based on the degree of off‐flavour perceived. The E‐nose was used to correlate the sensory data and the sensor responses for the various resin grades, using multivariate statistical techniques. A good correlation was obtained between the E‐nose sensor responses and the human sensory analysis data, when the resins were analysed using standardized experimental run conditions. The method is capable of predicting the quality of an unknown food‐grade HDPE resin sample, in terms of its possibility of producing an off‐flavour in drinking water, which could be a result of migration of low molecular weight compounds from the polymer. Copyright © 2006 John Wiley & Sons, Ltd.     

新颖的仿生检测技术--电子鼻

电子鼻是一种新颖的模拟人的嗅觉来分析、识别和检测复杂嗅味和挥发性成份的仪器,通过人的鼻子和电子鼻的比较,详细介绍了电子鼻的基本原理和组成．通过对电子鼻与普通化学分析仪器的比较,了解电子鼻的应用领域．并列举了目前的一些应用．     

Integral approach for optimizing modified atmosphere packages for elstar apples: A combination of product and packaging constraints

Modified atmosphere packages with Elstar apples in various packaging systems have been investigated. Loss of firmness during shelf-life is used as the quality aspect to judge the performance of the modified atmosphere packages. A system-oriented model is derived that describes the experimentally found concentrations well. In the overall approach the time dependency of the oxygen and carbon-dioxide concentrations are discussed. It is shown that the quality attribute, the softening of apples, can be affected by the choice of packaging material. Hence this approach can be used to optimize modified atmosphere packaging of Elstar apples.     

A portable electronic nose based on embedded PC technology and GNU/Linux: hardware, software and applications

This paper describes a portable electronic nose based on embedded PC technology. The instrument combines a small footprint with the versatility offered by embedded technology in terms of software development and digital communications services. A summary of the proposed hardware and software solutions is provided with an emphasis on data processing. Data evaluation procedures available in the instrument include automatic feature selection by means of SFFS, feature extraction with linear discriminant analysis (LDA) and principal component analysis (PCA), multi-component analysis with partial least squares (PLS) and classification through k-NN and Gaussian mixture models. In terms of instrumentation, the instrument makes use of temperature modulation to improve the selectivity of commercial metal oxide gas sensors. Field applications of the instrument, including experimental results, are also presented.     

1-MCP对不同地域寒富苹果质地的响应

目的 研究1-甲基环丙烯（1-Methylcyclopropene,1-MCP）处理及山地种植对寒富苹果质地的影响。方法 以平地寒富和山地寒富果实为实验材料,应用质地多面分析（TPA）和穿刺法（TA）对苹果果肉质地进行研究,应用SIMCA软件对原始数据进行多变量分析,包括主成分分析（PCA）和正交-偏最小二乘判别分析（OPLS-DA）,寻找经不同处理后苹果果实的质地差异,并探讨1-MCP对2种寒富果实成熟软化及相关细胞壁酶（纤维素酶）、胞内酶（淀粉酶）活性的影响。结果 多变量统计分析结果显示,平地和山地寒富果实的质地在脆度、硬度、果皮脆性、胶性、咀嚼性等5项参数上差异显著。与对照组（CK）相比,山地寒富苹果在脆度、硬度、胶性等参数上显著高于平地寒富苹果（P<0.05）,经1-MCP处理后,山地寒富苹果在硬度、胶性、脆度、咀嚼性及果皮脆度上均高于平地寒富苹果。1-MCP处理可以显著抑制果实的软化,以及纤维素酶（Cx）和淀粉酶的活性,将贮后货架时间延长至28 d,其中山地寒富果实的纤维素酶（Cx）和淀粉酶活性低于平地寒富果实。结论 经1-MCP处理后,山地寒富果实在质地上好于平地寒富果实,更能延缓果实的软化。     

Design and test of an electronic nose for monitoring the air quality in the international space station

Long-term manned space missions requires a continuous monitoring of the air quality inside the spacecraft. For this scope, among several different solutions, electronic noses have been considered. On behalf of European Space Agency an electronic nose specifically designed for air quality control in closed environment is under development. After several ground experiments concerning the monitoring of a biofilter efficiency, the instrument has been tested during the ENEIDE mission on board of the International Space Station. in this paper the instrument main concepts and its performance in ground and space experiments are illustrated.     

Discrimination between different samples of olive oil using variable selection techniques and modified fuzzy artmap neural networks

An electronic nose for classification of olive oil samples is presented. Principal component analysis and a modified fuzzy artmap neural network where applied to data acquired from 12 sensors. A custom designed variable selection technique was also used to boost performance. Ten different samples of olive oils were classified with 78% accuracy, and confusion occurred mostly between similar olive oils. Defective samples were separated from defect-free olive oil with 97% accuracy. These results show that careful variable selection, coupled to a modified fuzzy artmap algorithm, can significantly improve electronic nose performance.     

A conductive polymer based electronic nose for early detection of Penicillium digitatum in post-harvest oranges

We describe the construction of an electronic nose, comprising four chemiresistive sensors formed by the deposition of thin conductive polymer films onto interdigitated electrodes, attached to a personal computer via a data acquisition board. This e-nose was used to detect biodeterioration of oranges colonized by Penicillium digitatum. Significant responses were obtained after only 24 h of incubation i.e. at an early stage of biodeterioration, enabling remedial measures to be taken in storage facilities and efficiently distinguishing between good and poor quality fruits.The instrument has a very low analysis time of 40 s.     

Application of a portable electronic nose system to assess the freshness of Moroccan sardines

In this paper, we propose the investigation and the realisation of an electronic nose system able to evaluate fish freshness in real-time, under the constraints of being suitable for miniaturization and portability. Six tin oxide based Taguchi gas sensors are used to analyse sardine samples stored at 4 °C. A dedicated real-time data acquisition system based on a microcontroller and portable computer have been designed and constructed for this application. Principal component analysis (PCA) and support vector machines (SVMs) results show that the system is able to assess the freshness of sardines stored at 4 °C.     

Active packaging technology to retain storage quality of pear cv. “Bartlett” during shelf-life periods under ambient holding after periodic cold storage

Response of “Bartlett” pears harvested at commercial maturity (104.29-N firmness and 3.15 starch iodine rating) to various active packaging conditions using O₂ (Fe powder) and ethylene (KMnO₄) scavenger sachets in low-density polyethylene (LDPE) film bags (25.4 and 50.8 μm), cold storage (2 ± 1°C with 95 ± 2%), and shelf-life holding periods under ambient conditions (24 ± 3°C; 68 ± 5% relative humidity [RH]) was recorded as changes in physic chemical parameters. The fruits were packed in 25.4- and 50.8-μm LDPE film bags containing 5%, 10%, and 15% Fe and KMnO₄ powder incorporated on silica as inert carrier in form of sachets. After packaging the fruits airtight in film bags, they were placed in corrugated fiber board (CFB) boxes (29 × 23 × 14 cm; L × B × H). Fruits packed in 50.8-μm LDPE film bags with sachets containing 15% Fe powder recorded maximum fruit firmness, total soluble solids (TSS), titratable acidity, and ascorbic acid with minimum spoilage, weight loss (physiological loss of weight [PLW]), pectin methylesterase (PME), polygalacturonase (PG) activity, and respiration rate and increase in fruit calcium content and highest level of overall acceptability (color, taste, aroma, and texture) after periodic cold storage and ambient shelf-life periods. The effect of different treatments was compared by post hoc analysis using Tukey's test, which also revealed significant differences among different treatments. Our findings also revealed that pear fruit retains edible quality until fruit firmness > 30.89 N, TSS > 10.0%, and weight loss < 9.00%.     

Qualité de pêches au sirop appertisées élaborées à partir de fruits congelés entiers — étude à l'échelon industriel

In order that a fruit syrup canning plant can function all year round, whole, frozen, unpeeled peaches were used as raw material. Studies were carried out on an industrial scale with six clones of clingstone peaches. They showed that when fruits have been partially thawed at −4°C to −1°C. stoning is possible with the existing machinery. Thawing is short and easily controllable with a microwave tunnel oven.Chemical peeling and sterilization are as easy as with fresh fruit and the quality of finished products is equivalent. The cost price of this treatment is lower than that of the conventional process used for manufacture of mixed canned fruits.     

TOF-SIMS analysis of a 576 micropatterned copolymer array to reveal surface moieties that control wettability

Time-of-flight secondary ion mass spectrometry (TOF-SIMS) was used in a high-throughput fashion to obtain mass spectra from the surfaces of 576 novel acrylate-based polymers, synthesized using a combinatorial approach and in a micropatterned format. To identify variations in surface chemistry within the library, principal component analysis (PCA) was used. PCA clearly identified surface chemical commonality and differences within the library. The TOF-SIMS spectra were also used to determine the relationship between water contact angle (WCA) and the surface chemistry of the polymer library using partial least-squares regression (PLS). A good correlation between the TOF-SIMS data from the novel polymers and water contact angle was obtained. Examination of the PLS regression vector allowed surface moieties that correlate with high and low WCA to be identified. This in turn provided an insight into molecular structures that significantly influence wettability. This study demonstrates that multivariate analysis can be successfully applied to TOF-SIMS data from a large library of samples and highlights the potential of these techniques for building complex surface property/chemistry models.     

二氧化氯对香梨贮藏后期品质保持效果的研究

目的研究二氧化氯气体处理对库尔勒香梨贮藏后期品质保持效果的影响。方法以新疆库尔勒香梨为实验材料,在(0±0.5)℃条件下,采用质量浓度为0,130.43,260.86,391.29 mg/m^3的二氧化氯气体处理库尔勒香梨。结果实验结果表明,适宜的二氧化氯气体浓度处理能有效降低香梨的质量损失率,保持较好的色泽,有效减缓香梨可溶性固形物、可滴定酸、Vc、叶绿素等含量的消耗,增强过氧化物酶(Peroxidase, POD)的活性,抑制多酚氧化酶(Polyphenol oxidase, PPO)的活性。其中质量浓度为130.43mg/m^3的处理效果最佳。结论采用二氧化氯处理库尔勒香梨,有利于保持果实的品质,进而延长了货架期。     

Toward the nanoscopic "electronic nose": hydrogen vs carbon monoxide discrimination with an array of individual metal oxide nano- and mesowire sensors

The array of chemiresistors made of individual pristine SnO2, surface doped (Ni)-SnO2 nanowires, and TiO2 and In2O3 mesoscopic whiskers was fabricated on a Si/SiO2 wafer. Their conductance was measured under pulses of H2 and CO reducing gases in oxygen as background gas. The nanostructures were shown to be n-type semiconductors possessing high sensitivity to the target gases. Following the "electronic nose" concept, correlation analysis of response of three-chemiresistor array is shown to be sufficient to discriminate between H2 and CO signals.     

Measurement of the absorption and scattering properties of turbid liquid foods using hyperspectral imaging

A hyperspectral imaging system in line scanning mode was used for measuring the absorption and scattering properties of turbid food materials over the visible and near-infrared region of 530-900 nm. An instrumental calibration procedure was developed to compensate for the nonuniform instrument response of the imaging system. A nonlinear curve-fitting algorithm for a steady-state diffusion theory model was proposed to determine absorption (mua) and reduced scattering coefficients (mu's) from the spatially resolved hyperspectral reflectance profiles. The hyperspectral imaging system provided good measurement of mua and mu's for the simulation samples made of Intralipid scattering material and three absorbers (blue dye, green dye, and black ink) with average fitting errors of 16% and 11%, respectively. The optical properties of the fruit and vegetable juices and milks were determined. Values of the absorption and reduced scattering coefficient at 600 nm were highly correlated to the fat content of the milk samples with the correlation coefficient of 0.995 and 0.998, respectively. Compared to time-resolved and frequency-domain techniques, the hyperspectral imaging technique provides a faster and simpler means for measuring the optical properties of turbid food and agricultural products.     

近红外漫反射式水果糖份含量的测量系统

基于近红外光谱技术而建立水果糖份含量的测量系统,主要包括FT-IR光谱仪、光纤漫 反射附件和数据采集卡。利用该系统对56个苹果糖份含量进行了预测试验, 结果为:标准校正误差为0.317,标准预测误差为0.487。该测量系统可以直接用于水果糖份含量的快速定量分析且预测精确度可达到95%。     

基于近红外光谱的不同产地苹果货架期鉴别方法

提出了一种基于近红外漫反射光谱技术的不同产地苹果货架期鉴别方法.从市场上购买山东和陕西的富士苹果各20个,分别对购买当日和存放1周(7d)后的样品进行光谱测试,分析表明一周后不同品种样品光谱在1 420am和1 630nm处吸光度值均有不同程度的增大.通过主成分分析研究了样品产地对不同货架期样品光谱的影响,将总贡献率为...