胶态金纳米型时间-温度指示器性能研究

目的 探究基于金纳米颗粒的时间温度指示器（Time-temperature indicator, TTI）的变色机理及不同制备参数对其动力学参数的影响,为其在食品上的实际应用提供参考依据。方法 以明胶与氯金酸的还原反应为基础制备胶态金纳米型时间-温度指示器。通过紫外-可见分光光度计对TTI的吸光度进行测定,并将其与时间进行非线性拟合。采用单因素实验探讨制备参数对反应速率、变色寿命和活化能的影响。结果 TTI体系中生成的金纳米颗粒使得TTI呈现紫红色,金纳米颗粒数量的增加导致TTI的颜色变深。明胶用量减少而明胶-氯金酸质量比不变,以及明胶用量不变而明胶-氯金酸质量比增大的情况下,TTI体系的反应速率变慢,变色寿命延长。明胶-氯金酸质量比决定了TTI体系的活化能。TTI的活化能的范围为77.89～84.58 kJ/mol。结论 TTI具有监测因脂肪氧化而变质食品的潜能,通过调节TTI的制备参数可改变其变色寿命以匹配不同货架期的食品。     

European Consumers' Perceptions of Time–Temperature Indicators in Food Packaging

Food quality is an essential aspect of the food industry. Time–temperature indicator (TTI) technology has the capability to provide information on temperature fluctuations that temperature‐sensitive food products have undergone. However, the adoption of the TTI technology in the consumer market has yet to materialize despite the many benefits that TTIs bring to food manufacturers, retailers and consumers. One of the reasons for this could be the general lack of knowledge regarding consumers' perceptions of TTIs. The aim of this study is to understand the consumers' knowledge, interest and perceptions of TTIs. To reach this aim, 16 focus group discussions and a quantitative survey were conducted in four European countries (Finland, Greece, France and Germany) during May–October 2012. Consumers' views on both the TTI technology concept and two commercially available TTI applications were studied. The results of the study show that consumers in all countries appreciate and understand TTI technology and associate differing benefits with it, especially so in warmer countries. On the other hand, the studied applications did not meet all consumers' expectations implying the need for further work to enable TTIs to gain a wider acceptance. Copyright © 2014 John Wiley & Sons, Ltd.     

没食子酸时间温度指示器的制备及性能研究

目的 基于没食子酸(Gallic Acid,GA)的特性,制备可以通过调节pH值改变活化能的时间温度指示器(Time Temperature Indicator,TTI),以期为新型TTI的开发提供参考。方法 制备不同GA浓度、pH值的GA TTI,在恒温条件下储藏,探究GA浓度和pH值对TTI颜色变化的影响。测定制备TTI的吸光度值,构建TTI颜色响应的温度动力学模型,并确定其动力学参数和活化能。结果 GA浓度为0.02 mol/L时TTI对温度最为敏感,故制备出GA浓度为0.02 mol/L,pH值为6.5、7.0、7.5、8.0的4种TTI。pH值为6.5时,TTI从无色变为黄褐色;pH值为7.0时,TTI从无色变为草绿色;pH值为7.5和8.0时,TTI从无色变为蓝绿色。利用吸光度计算出的4种TTI的活化能分别为85.99、44.93、29.57、25.03 kJ/mol。结论 不同pH值的GA TTI颜色变化明显,且GA TTI活化能有一个较大的范围,适用食品类型广泛,有潜力作为一种新型TTI。     

Performances of time–temperature indicators in the study of temperature exposure of packaged fresh foods

The diffusion of time–temperature indicators (TTIs), attached as labels onto the packages of perishable food and non‐food products (intelligent packaging), is growing more and more. Aside from checking product shelf‐life, TTI devices can be used to monitor the distribution chain in real conditions. In this respect, the performances of some very common TTIs (A 12 Fresh Check, Lifelines Technologies) were extensively investigated in this work. The aim was to establish a procedure for an accurate, objective and reproducible estimate of the darkening progress of the sensitive area of the indicators and to discover a reliable data treatment to estimate the ‘effective temperature’, T_eff, namely a fictitious average temperature that can replace the overall temperature fluctuations experienced by a packaged fresh food. The image analysis approach was found very useful for an accurate and sensitive definition of the information provided by the indicators, leading to the evidence of a very slow darkening of the sensitive region, even at ?22°C. The kinetic parameterization of TTI responses was implemented in an EXCEL worksheet so as to directly evaluate T_eff on the basis of a set of label brightness values acquired by image analysis. Comparing the calculated ‘effective temperature’ with the average temperature recorded with conventional devices, the reliability of the TTI tags and the accuracy of this procedure was demonstrated. Taking into account the low cost of the TTI tags, their wide usage can be suggested to monitor the various steps of the real distribution chain of a given product, namely, transport, bench and home storage. Copyright © 2001 John Wiley & Sons, Ltd.     

ASTM thermal insulation conference

Rapid world wide development of the cold chain on a large scale is necessary to assure proper food supply to fast growing populations. There is sufficient technical information available to do this properly; the problems are mainly economic and political. But even so there is a great need to develop the scientific base further.Although there exists a vast amount of data concerning proper storage conditions for different kinds of food, there is still much to learn. This is particularly true for living produce such as fruit and vegetables, where the number of varieties and differences caused by growing conditions are tremendous. The composition of the atmosphere is sometimes as important as temperature and many additional treatments may be used in order to improve the keeping quality. Frozen foods are much more stable and in many ways simpler to handle, but present some difficult quality control problems.While chilling, freezing and cold storage are relatively simple procedures and can be done very economically on a large scale, the problems are greater in transport and distribution. Further improvements are required to combine satisfactory quality protection and acceptable costs in scattered small scale operation. The retail sales equipment in particular needs careful attention.     

New LSB-based colour image steganography method to enhance the efficiency in payload capacity,security and integrity check

Steganography is the technique for hiding information within a carrier file so that it is imperceptible for unauthorized parties. In this study, it is intended to combine many techniques to gather a new method for colour image steganography to obtain enhanced efficiency, attain increased payload capacity, posses integrity check and security with cryptography at the same time. Proposed work supports many different formats as payload. In the proposed method, the codeword is firstly formed with secret data and its CRC-32 checksum, then the codeword is compressed by Gzip just before encrypting it by AES, and it is finally added to encrypted header information for further process and then embedded into the cover image. Embedding the encrypted data and header information process utilizes Fisher-Yates Shuffle algorithm for selecting next pixel location. To hide one byte, different LSB (least significant bits) of all colour channels of the selected pixel is exploited. In order to evaluate the proposed method, comparative performance tests are carried out against different spatial image steganographic techniques using some of the well-known image quality metrics. For security analysis, histogram, enhanced LSB and Chi-square analyses are carried out. The results indicate that with the proposed method has an improved payload capacity, security and integrity check for common problems of simple LSB method. Moreover, it has been shown that the proposed method increases the visual quality of the stego image when compared to other studied methods, and makes the secret message difficult to be discovered.     

Fabrication and Characteristics of Microbial Time Temperature Indicators from Bio‐Paste Using Screen Printing Method

Screen printing method was employed to produce microbial time temperature indicators (TTI). Bio‐pastes containing lactic acid bacteria loaded Ca‐alginate microparticles (LCAMs) and suitable for printing on polymer films have been produced. Through a spray‐solidification method, polysaccharide gel microparticles allowed for the efficient encapsulation of the lactic acid bacteria, which chromatically induced a colour change in the pH indicator. As the alginate concentration of LCAMs increased, the size of the microparticles decreased. The average diameter of LCAMs ranged from (1.67 ± 0.15) × 10³ to (2.93 ± 0.31) × 10³ nm. For the evaluation of bio‐pastes, the contact angles and lactic acid production properties were determined. Lower contact angles were obtained with decreasing pullulan concentration, indicating the increase in wettability for printing. The curve of lactic acid production by alginate immobilized cells was determined to take place as a zero‐order reaction favourable to TTI colour change. Visibility of TTIs was greatly improved at microencapsulation sites. As the size of the LCAMs was decreased, the visibility was found to be improved. The Arrhenius activation energy (Ea) of CIFP009‐based TTI was 117 kJ/mol. The results show that the developed manufacturing method would be used for an industrialized, simple and low‐cost manufacturing method for microbial TTIs. Copyright © 2013 John Wiley & Sons, Ltd.     

Dehazing of remote sensing images using improved restoration model based dark channel prior

Haze degrades visual information of remotely sensed images. Therefore, haze removal is a demanding and significant task for visual multispectral information improvement. The existing haze removal techniques utilize different restrictions and before restoring hazy images in an efficient manner. The review of existing haze removal methods demonstrates that the haze-free images suffer from colour distortion and halo artefacts problems. To solve these issues, an improved restoration model based dark channel prior is proposed in this paper. The proposed technique has redefined transmission map, with the aim to reduce the colour distortion problem. The modified joint trilateral filter is also utilized to improve the coarse estimated atmospheric veil. The experimental results reveal that the proposed approach provides visually significant haze-free images and also preserves the significant detail.     

A solid‐state time‐temperature indicator used in chilled fresh pork monitoring

A solid‐state enzymatic time‐temperature indicator (TTI) was developed in this paper. Glucoamylase microcapsules, emulsifier, and substrate solution were mixed uniformly, then the mixture was coated on a paper and could be activated by an agar cover. Both single factors and orthogonal experiments were conducted to obtain qualified formulations whose endpoints ranged from 5 to 6 days with storage temperature maintained at 4°C. The Arrhenius activation energy (E_A) of obtained TTIs was also calculated at 107, 97.5, 88.0, 107, 98.5, 87.7, and 89.7 kJ/mol. For the application of TTIs to chilled fresh pork monitoring, both the spoilage mechanism and kinetic properties of pork were studied and an E_A value of 64.7 kJ/mol was obtained. After isothermal verification, a qualified TTI formulation was obtained, of which the mass of glucoamylase microcapsules was 0.02 g, the mass of amylose was 5 g, the concentration of iodine solution was 0.1M, and the thickness of agar cover was 2 mm. The time‐temperature history of chilled fresh pork can be indicated by the colour response of the TTI.     

Colour Reproduction as a Function of Tone Scale in Negative-Positive and Reversal Systems

The object of this study is to provide o method for simulating the whole process of colour reproduction in a mathematical way, so that at any moment well-chosen changes can be introduced into the different steps of this process. This approach provides certain possiblities, when testing the quality of colour reproduction by colour material, which are not yet afforded with the required accuracy by empirical means.     

时间–温度指示器在冷链运输中的应用进展

目的 研究时间–温度指示器(Time-Temperature Indicator,TTI)在产品包装和冷链物流中的价值和意义,并对冷链物流过程实施严格的监控义,以保障公众医疗卫生安全和食品卫生安全。方法 简述几种常见TTI的类型及原理,并概述TTI的研究现状,同时总结TTI技术的发展趋势并对其在我国的商用前景进行展望。结果 TTI历经几十年的发展技术已较为成熟,已在冷链运输、物流管理等领域发挥很大作用。结论 TTI技术的应用和发展前景广阔,与智能包装、物流管理等领域的技术结合发展会加速其在我国的商业化进程。     

Hiding a secret colour image in two colour images

Abstract

Visual cryptography is different from traditional cryptography. That is, neither time-consuming computation nor complex cryptographic knowledge is needed. Stacking is the only operation required to recover a secret image, and the individual image does not give the hackers any information about the secret image. None of researches tried to deal with meaningful colour share transparencies. Hence, two methods are proposed for hiding a colour image in two meaningful colour share transparencies in this paper. To achieve this goal, the colour decomposition approach and halftone technology are first applied to cope with secret colour images. Then the concept of the human visual system is utilized to generate two colour meaningful sharing transparencies. To support various applications, two variants are presented. The first proposed method, method-1, is suitable for simple colour images, and the second, method-2, provides better visibility of complex colour images.     

Nanomaterials in Smart Packaging Applications: A Review

Food wastage is a critical and world-wide issue resulting from an excess of food supply, poor food storage, poor marketing, and unstable markets. Since food quality depends on consumer standards, it becomes necessary to monitor the quality to ensure it meets those standards. Embedding sensors with active nanomaterials in food packaging enables customers to monitor the quality of their food in real-time. Though there are many different sensors that can monitor food quality and safety, pH sensors and time-temperature indicators (TTIs) are the most critical metrics in indicating quality. This review showcases some of the recent progress, their importance, preconditions, and the various future needs of pH sensors and TTIs in food packaging for smart sensors in food packaging applications. In discussing these topics, this review includes the materials used to make these sensors, which vary from polymers, metals, metal-oxides, carbon-based materials; and their modes of fabrication, ranging from thin or thick film deposition methods, solution-based chemistry, and electrodeposition. By discussing the use of these materials, novel fabrication process, and problems for the two sensors, this review offers solutions to a brighter future for the use of nanomaterials for pH indicator and TTIs in food packaging applications.     

微生物型鲜牛奶时间温度指示器

目的为了准确表征鲜牛奶的新鲜度,制备一种微生物型时间-温度指示器。方法选择瑞士乳杆菌菌种作为微生物基础,采用SPG膜乳化技术制备微生物微胶囊,按照微生物胶囊与固体基质的不同比例制作3种固体微生物时间-温度指示器,以色差值为变化参数研究其动力学特性,并与应用的鲜牛奶在恒温及变温条件下进行匹配试验。结果 3种不同比例时间-温度指示器的活化能与鲜牛奶的活化能差值在25 kJ/mol之内,其中当微胶囊质量与固体基质体积之比(g/mL)为1∶2时,在变温条件下两者的等效温度差值为2.1℃,TTI预测食品货架期终点的误差为3%。结论在恒温和变温等2种条件下时,制备的微生物型TTI可以精准实现鲜牛奶货架期的可视化。     

Time temperature indicators made with sublimating azulene derivatives as the functional dye for use of fast reaction rate

Time temperature indicators (TTIs) based on a dye sublimation process have been developed for full time monitoring of heat sensitive vaccines with shorter shelf-life during cold chain transportation and storage. The structure of TTI and the methods to make the TTI are introduced. TTI 1 and TTI 2 introduced in the article were made with methyl azulene-1-carboxylate and methyl 3-methylazulene-1-carboxylate as the functional dyes, respectively. The kinetic parameters of TTI 1 and TTI 2 were studied. To achieve a change of 30 in ∆E*ab, it takes 9.1 h at 37°C, 39.7 h at 25°C, 5.61 days at 15°C and 23.3 days at 5°C for TTI 1 and 37.2 h at 37°C, 128.8 h at 25°C, 37.5 days at 15°C and 102.5 days at 5°C for TTI 2. The activation energies (E_a) are calculated to be 91.87 kJ mol⁻¹ and 97.99 kJ mol⁻¹ for TTI 1 and TTI 2, respectively. A field simulation study was conducted on TTI 2 associated with bivalent oral polio vaccine (bOPV), yielding excellent correlation between the reaction rate of TTI 2 and the titre change of bOPV.     

Modelling of food transportation systems – a review

In 2002, over a million refrigerated road vehicles, 400,000 refrigerated containers and many thousands of other forms of refrigerated transport systems are used to distribute chilled and frozen foods throughout the world. All these transportation systems are expected to maintain the temperature of the food within close limits to ensure its optimum safety and high quality shelf life.Increasingly, modelling is being used to aid the design and optimisation of food refrigeration systems. Much of this effort has concentrated on the modelling of refrigeration processes that change the temperature of the food such as chilling, freezing and thawing. The purpose of a refrigerated transport system is to maintain the temperature of the food and appears to have attracted less attention from modellers. This paper reviews the work that has been carried out specifically on the modelling of food temperature, microbial growth and other parameters in the transportation of food.     

冷藏车开门时车内温湿度变化实验研究

配送过程中冷藏车开门时的热质交换会引起车内空气温湿度的剧烈变化,这使得食品的品质难以得到保证.针对目前冷藏车开门卸货时存在的一些问题,进行了对比实验,对不同条件下的车内温度、相对湿度变化进行了分析,得出在开门时长一定的情况下车厢内外空气温差是影响车内温升的主要因素,采用PVC门帘可以有效地抑制车内温度升高,一定程度上保证食品安全.     

Identification of change structure in statistical process control

In order to diagnose properly quality problems that occur in manufacturing the diagnostician, be it human or computer, must be privy to various sources of information about the process and its behaviour. This paper describes how neural networks and Bayesian discriminant function techniques can be used to provide knowledge of how a product characteristic changed, i.e. shift in mean or variability, when so noted by the control chart application. Such information is useful because there usually exists some underyling knowledge about the physical phenomena in question that relates the behaviour of the observed characteristic to its processing variables. When a change in the process is detected by the appropriate statistical method, a feature vector of process-related statistics is used to identify the change structure as a shift in mean or variance. This paper addresses various issues concerned with this problem, namely: process change detection, feature vector selection, training patterns, and error rates. Simulation experiments are used to test various hypotheses and also compare the effectiveness of the two proposed approaches against two simpler heuristics. Results show the neural network and quadratic discriminant function approaches to be fairly similar, with a success rate of 94% and both to be superior to the simpler heuristic approaches.     

Underexposed and overexposed colour image enhancement using information set theory

This paper presents a new approach for improving the contrast of digital colour images in extreme lighting environment. The concept of information sets that are derived from fuzzy sets is applied for this purpose. The S and V components of the HSV (hue, saturation, value) colour model are fuzzified using Gaussian and triangular membership functions but H is preserved. Objective measures like contrast information, quality and visual factor (V_f) are defined to represent the image characteristics. A new entropy function and V_f are used to form the objective function which is optimised using particle swarm optimisation to learn the image-specific parameters required for the enhancement. These new measures defined here serve to evaluate the performance of the proposed algorithm. In addition to preserving the colour and specific image features, the subjective and objective evaluations clearly depict the improvement in the quality of both the underexposed and overexposed images. On comparison, it is found that the proposed technique outperforms the existing techniques in terms of entropy, information measure and mean opinion score.     

Road sign detection using eigen colour

A novel colour-based method to detect road signs directly from videos is presented. A road sign is usually painted with different colours to show its functionalities. To detect it, different detectors should be designed to deal with its colour changes. A statistic linear model of colour change space that makes road sign colours be more compact and thus sufficiently concentrated on a smaller area is presented. On this model, only one detector is needed to detect different road signs even though their colours are different. The model is global and can be used to detect any new road signs. The colour model is invariant to different perspective effects and occlusions. After that, a radial basis function (RBF) network is then used to train a classifier to find all possible road sign candidates from road scenes. Furthermore, a verification process is applied to verify each candidate using its contour feature. After verification, a rectification process is used for rectifying each skewed road sign so that its embedded texts can be well segmented and recognised. Due to the filtering effect of the proposed colour model, different road signs can be very efficiently and effectively detected from videos. Experimental results have proved that the proposed method is robust, accurate and powerful in road sign detection.