Biosensors fob food industry

Novel biosensor systems were constructed for food industry. In order to determine fish freshness, a multifunctional enzyme sensor system was developed by combining a double membrane consisting of a 5'‐nucleotidase membrane and a nucleoside phosphorylase‐xanthine oxidase membrane with an oxygen electrode. Each nucleotide concentration was determined as the current decreased. One assay was completed within 20 min. Good comparative results were observed between the KI values determined by the sensor proposed and by the conventional method. An enzyme sensor for meat freshness consisted of a monoamine oxidase‐collagen membrane and an oxygen electrode. The response time of the electrode was 4 min. A linear relationship was observed between the amine (tyramine) concentration in the range 50–200 μM and the difference in current. Monoamine in meat extract was determined by the enzyme sensor. Micro‐glutamate sensor was constructed using silicon fabrication technology. Calibration curve for glutamate sensor was obtained in a glutamate concentration range between 5–50 mM. Moreover, an immuno sensor based on piezoelectric crystal was applied to the determination of toxic bacterium C. albicans. The frequency shift is correlated with C. albicans concentration in the range 10⁶ 5×10⁸ cell/ml.     

鱼肉鲜度测定方法研究进展

综述了用于鱼肉鲜度测定的几类不同方法 ,包括感官评价方法、微生物学方法、物理和化学方法和生物传感器方法等 ,并比较了不同测定方法的特点 ,阐明了鱼肉鲜度测定方法的未来发展趋势。     

Amperometric Determination of Fish Freshness by a Hypoxanthine Biosensor

The traditional determination of fish freshness is to detect total volatile basic nitrogen, microbial load or hypoxanthine. These methods are complex and expensive. A hypoxanthine biosensor was constructed by using immobilised xanthine oxidase and a platinum electrode. The enzyme was immobilised on a silk membrane. The electrode detected the hydrogen peroxide released during the enzymatic reaction. A linear range from 0·05 to 100×10⁻⁶ M of hypoxanthine was observed. When the method was applied to fish samples, the results obtained agreed well with those obtained by the conventional total volatile basic nitrogen and microbial load. This biosensor provides a reliable, simple, rapid and economical method for the measurement of fish freshness.     

Recent Advances in Methods and Techniques for Freshness Quality Determination and Evaluation of Fish and Fish Fillets: A Review

The freshness quality of fish plays an important role in human health and the acceptance of consumers as well as in international fishery trade. Recently, with food safety becoming a critical issue of great concern in the world, determination and evaluation of fish freshness is much more significant in research and development. This review renovates and concentrates recent advances of evaluating methods for fish freshness as affected by preharvest and postharvest factors and highlights the determination methods for fish freshness including sensory evaluation, microbial inspection, chemical measurements of moisture content, volatile compounds, protein changes, lipid oxidation, and adenosine triphosphate (ATP) decomposition (K value), physical measurements, and foreign material contamination detection. Moreover, the advantages and disadvantages of these methods and techniques are compared and discussed and some viewpoints about the current work and future trends are also presented.     

A novel technique for rapid evaluation of fish freshness using colorimetric sensor array

An olfaction system based on colorimetric sensor array was developed for fish freshness evaluation. Nine chemically responsive dyes were selected according to their sensitivity to volatile compounds typically occurring during spoilage in fish. The colorimetric sensor array was made by printing selected dyes on a reverse phase silica gel plate. Detection on fish of chub was made every 24 h within seven days. A color change profile for each sample was obtained by differentiating the images of the sensor array before and after exposure to the odor of sample. The digital data representing the color change profiles for the fish samples were analyzed using principal component analysis. The chub samples were classified into three freshness groups using a radial basis function neural network, with an overall classification accuracy of 87.5%. This research suggests that the system is useful for quality evaluation of fish and perhaps other food containing high protein.     

基于阳极氧化铝比色阵列传感器对鱼肉新鲜度的测定

为了快速、准确地对鱼肉新鲜度进行无损实时监测,本研究以阳极氧化铝片为基材,选取13种指示剂作为气敏材料,构建了一种可视化比色阵列传感器。利用所构建的比色阵列传感器对贮藏过程中大菱鲆鱼肉新鲜度进行测定。结果表明,在25 ℃条件下,当贮藏时间超过22 h时,鱼肉的总挥发性盐基氮（TVB-N）含量达到32.85 mg/100 g,鱼肉发生腐败变质,此时的比色阵列传感器中的阵列点发生颜色变化。提取阵列点在响应前后的红、绿、蓝（Red、Green、Blue,RGB）值并进行差减,对其进行聚类分析和主成分分析。结果表明,该传感阵列能够准确区分不同贮藏时间段的鱼肉新鲜度。此外,将该阵列传感器应用于不同贮藏时间下鲤鱼和美国红鱼新鲜度的检测,结果表明通过传感阵列预测的TVB-N值与实际测量值之间没有显著性差异。因此,将该传感器应用于鱼肉新鲜度监测具有可行性。     

Mathematical models for the trimethylamine (TMA) formation on packed cod fish fillets at different temperatures

The microbial formation of trimethylamine (TMA) can be used as a quality indicator compound to predict the freshness of fish during its shelf life. In a supply chain with fluctuating temperatures, mathematical models will be valuable tools to simulate this formation as a function of temperature and time. These models are essential to link sensor data on the formation of TMA to the actual freshness of fish. Existing models for the formation of TMA in fish needed improvements and secondary models for the effect of temperature on the formation of TMA are lacking in the literature. Three different approaches were evaluated on their ability to simulate the experimental observed TMA formation at 4 different temperatures (0, 5, 10 and 15 °C). In the first approach the existing models were improved and the temperature effect was modelled by an empirical model using four parameters. This model is able to simulate the TMA formation at static temperatures. Since TMA is produced on fresh cod fillets by the micro-organisms Shewanella putrefaciens and Photobacterium phosphoreum the microbial Baranyi–Roberts model was initially used for modelling the TMA formation, but this model was found to be too complex (too many correlated parameters that could not be estimated). In the third approach it was seen that a simplified Baranyi–Roberts model with only three parameters could be used to predict the TMA formation with equal accuracy. The influence of the temperature on the parameter μ_max was modelled using the extended square root model of Ratkowsky and the differences in TMA formation profiles of different batches could be described by the batch specific parameter N₀ representing the initial quality. The presented dynamic model is valuable in predicting the formation of TMA in a fresh fish supply chain with dynamic temperatures. This model has the potential to be used to link sensor data of TMA in the headspace to the actual freshness status of the fish.     

Effects of Freshness on the Cook Loss and Shrinkage of Grass Carp (Ctenopharyngodon idellus) Fillets Following Pasteurization

The effects of fish freshness (stored in ice for 0–18 days) on cook loss and shrinkage of grass carp (Ctenopharyngodon idellus) fillets following pasteurization treatments (70–90ºC, 0–60 min) were investigated. The cook loss and shrinkage of fish fillets increased with the severity of heat treatment, but decreased as the fish fillets became less fresh. A decrease in cook loss and shrinkage of fish muscles was tied to their changes in pH, total volatile base nitrogen and protein functionality. This study indicates the importance of using fish samples with consistent freshness in packaged pasteurized fish-based entrees.     

Monitoring the biogenic amines in Chinese traditional salted pork in jelly (Yao‐meat) by colorimetric sensor array based on nine natural pigments

To develop simple, cheap and convenient sensors for Yao‐meat freshness evaluation and biogenic amines (BAs) detection, a colorimetric sensor array was made by printing nine natural pigments on a hydrophobic nanoporous film. A colour change profile for each sample was obtained by differentiating the image of sensor array before and after exposure to volatile organic compounds (VOCs). The sensor array was exposed to atmospheres containing BAs vapours with concentrations over the range 10–30 ppm. Rosa chinensis extract possessed the highest sensitivity thanked to the highest anthocyanin contents. The results of principal component analysis (PCA) showed that the measurements corresponded to three freshness levels were separated clearly. The partial least‐squares prediction model was obtained with the correlation coefficients of 0.921 and 0.907 in calibration and validation sets, respectively. This research suggested that the anthocyanins content pigments maybe a very useful colorimetric sensor for quality evaluation of meat.     

Dual bacterial strains TTI for monitoring fish quality in food cold chain

Most microbial time–temperature indicators (TTIs) considered only one spoilage strain. This research compared single and dual spoilage strains-based microbial TTI for quality changes of chilled grouper fish (Epinephelus fuscoguttatus x E. lanceolatus) fillet products during distribution. The next-generation sequencing (NGS) and traditional plate count approach showed that Pseudomonas fragi and Vibrio parahaemolyticus were specific spoilage bacteria at 7 and 15°C. A dual-strain TTI response provides more accurate results than a single-strain TTI and provides an irreversible color change from yellow to reddish-brown, showing levels of fish freshness. The microbial TTI comprises fish spoilage bacteria strains with 3 log CFU/ml, a nutrient broth supplemented with 2% NaCl as a medium, and phenol red with 0.25 mg/ml as a pH indicator. Overall, this study points to the applicability of a dual-strain microbial TTI as a valuable tool for monitoring fish quality changes during cold chain break condition.     

Development of a smart packaging for the monitoring of fish spoilage

There is much interest from the fisheries industry in developing rapid methods to evaluate real-time freshness of fish and seafood products. Emphasis is on the ones that would reflect and account for the products history and their storage conditions from “harvest-to-home”. The development of a “smart packaging” that monitors the microbial breakdown products in the headspace of packaged fish is described. When fish spoils it releases a variety of basic volatile amines which are detectable with appropriate pH indicating sensors. These are prepared by entrapping within a polymer matrix a pH sensitive dye that responds, through visible color changes to the spoilage volatile compounds that contribute to a quantity known as total volatile basic nitrogen (TVB-N). Laboratory trials on fresh fish filets showed that the sensor accurately tracks the increase in amines concentration in the package headspace. The response was also found to correlate to changing microbial populations (total viable count or TVC and Pseudomonas spp.). In addition, leaching of the dye was assessed over time to assess the suitability of the sensor formulation for food packaging application.     

A nondestructive method for estimating freshness of freshwater fish

The traditional indictors of fish freshness including total aerobic count (TAC), K value, total volatile basic nitrogen (TVB-N), and sensory assessment (SA) were measured regularly to analyze the freshness changes during chill storage. Electric conduction property of whole fish was also studied by measuring their impedances under different frequencies as a fast nondestructive method. The relationship between traditional freshness indictors and electric conductivity was analyzed to determine the feasibility of evaluating fish freshness based on impedance change ratio (Q value) during storage. The results showed that traditional freshness indictors (TAC, K value, and TVB-N) values increased as storage time prolonged, while Q value and SA decreased. There were good relationships between Q value and TAC, K value, TVB-N, and SA (P < 0.01), with the correlation coefficients were 0.943, 0.996, 0.951, and 0.968, respectively. Thus, Q value can be used as a valid index for freshness evaluation and this method via measuring the electric conductivity property of whole fish is a fast nondestructive method for determining the freshness of fish during storage.     

Determination of Hypoxanthine in Fish Meat with an Enzyme Sensor

An enzyme sensor specific for hypoxanthine (Hx) was developed using immobilized xanthine oxidase-membrane and an oxygen probe. Xanthine oxidase (E.C. 1.2.3.2.) was covalently immobilized on a membrane prepared from cellulose triacetate, 1,8-diamino-4-aminomethyloctane, and glutaraldehyde. Hx is oxidized to uric acid by the immobilized enzyme, the output current of the oxygen probe decreasing due to oxygen consumption. A linear relationship was obtained between current decrease and Hx concentration in the range 0.06–1.5 mM. The enzyme sensor could be used for more than 100 assays without decrease of output current After 30-day-storage at 5°C, no remarkable decrease of output current was observed. The enzyme sensor system was applicable to the simple, rapid, and economical determination of Hx in several fish meats including sea bass, saurel, mackerel, yellowfish, and flounder.     

鱼体新鲜度近红外光谱检测方法的比较研究

目的 建立针对淡水鱼整鱼鱼体新鲜度的快速无损检测方法. 方法 通过比较不同的光谱与相应挥发性盐基氮(TVB-N)值的建模结果, 以及对比分析竞争性自适应重加权算法(CARS)、遗传算法(GA)及连续投影算法(SPA)三种特征波长选择方法对模型的优化结果, 对鱼鳞及光谱采集部位等影响因素进行研究。结果 鱼体有鳞时的尾部为最佳新鲜度检测部位。CARS法较优且鱼体新鲜度检测的最优波段为800~1100 nm, 采用CARS特征波长选择方法选择出23个波长变量重新建立PLS模型, 模型预测集相关系数RP=0.957, 预测均方根误差RMSEP=0.589 mg/100 g。利用CARS方法选择的23个波长变量对淡水鱼进行新鲜度评价, 准确率达96.67%。结论 该方法为淡水鱼整鱼新鲜度快速无损检测提供了一种有效的方法。     

Prolonging Shelf-Life of Carp by Combined Ionising Radiation and Refrigeration

Experiments were performed using ionisating radiation in order to prolong the shelf-life of two groups of refrigerated fish ( Cyprinus carpio ). After irradiation fish were kept at 0–2°C. Non-irradiated fish reached the non-acceptability point in 16 days and irradiated fish reached that point in 31 days. No difference was found between shelf-life of whole or eviscerated fish. If fish were immediately cooled to 0°C after death, their shelf-life was prolonged considerably. From this study it is clear that chemical tests of freshness such as TVB-N and K value determination are not appropriate for the study of irradiated fish. Organoleptic estimations and a new determination using an odour concentration meter seem to fit best the objective determination of freshness.     

Thermal Diffusivity Variation Study of Cold Stored Malaysian Pangasius Sutchi at 10°C

This paper presents the use of thermal diffusivity-variation of Malaysian Pangasius Sutchi freshwater fish as a criterion to estimate the freshness in fish marketing. A homogenous specified area of a fresh fish body was cut into slices which were wrapped and preserved in a cold store of 10°C for a period of 28 days. Ansari's approach has been found earlier as an appropriate one to measure the thermal diffusivity of fish through transient cooling. The daily measurement of those slices (samples) along the muscle orientation revealed that thermal diffusivity increased up to 3 days then stayed approximately constant up to the end of the preservation period (28 days). In the literature the shelf life was also found 3 days at 10°C, which in turn agreed with the present investigation. Regression analysis was made to develop an empirical correlation between thermal diffusivity ratio and preservation time of the fish under study. This correlation could be used by food technologists as an index of deterioration of freshness or consumer acceptance     

Original article: Gel properties of red tilapia surimi: effects of setting condition,fish freshness and frozen storage

This study aimed to determine effects of setting condition, fish freshness and storage time of frozen surimi on properties of red tilapia surimi gel. To investigate the effect of setting condition, a combination of eight setting temperatures (35–70 °C) and four setting times (30–120 min) was used. Maximum breaking force, deformation and gel strength were obtained after the gel had been set at 40 °C for 90 or 120 min. Setting at 65 °C resulted in the lowest obtained gel strength, because of proteolytic degradation of myosin heavy chain. Increasing storage time of raw fish material in ice caused a significant decrease in gel strength of the resultant surimi gel (P < 0.05). Gels produced from surimi kept in frozen storage for up to 9 months also exhibited reduced gel strength, with a concomitant increase in the expressible drip, with increasing storage time (P < 0.05).     

纳米卟啉在鱼新鲜度检测方面的应用

鱼类因其高蛋白、高水分活度的特点,极易发生腐败变质。变质后不仅使风味变差,还可能引起食物中毒而危及生命安全。因此,新鲜度则成为检测鱼质量的一个重要指标。本文主要综述了卟啉及其衍生物的结构性质、纳米卟啉的制备和性质及纳米卟啉在鱼新鲜度检测方面的应用。鱼新鲜度的检测方法包括化学指标检测法、感官评价法、物理检测法、微生物检测法等传统检测方法和仿生技术法、光谱法、生物阻抗法、电导法、生物技术法等新型检测方法。利用纳米卟啉来检测鱼新鲜度具有灵敏度高、成本低廉、检测过程方便快速等优点,在鱼新鲜度快速无损检测中将发挥巨大的作用。而纳米卟啉材料因其特殊的物理、化学性质,成为更具应用价值的气敏材料。     

Protein solubility and emulsifying capacity in frozen stored fish mince

Effect of initial freshness on the relationship between emulsifying capacity and protein solubility of frozen stored fish mince was investigated. The emulsifying capacity of proteins was significantly (P <0.05) affected by the initial freshness. A positive correlation (P <0.05) between protein solubility and the ability of the soluble proteins to emulsify and stabilise an emulsion was observed. Correlation between salt-soluble proteins and emulsifying capacity revealed that myofibrillar proteins (P <0.05) are the main proteins that decide the emulsion properties.     

Freshness characterisation of whiting (Merlangius merlangus) using an SPME/GC/MS method and a statistical multivariate approach

BACKGROUND: The freshness of whiting was studied at five stages of ice storage by comparing the analysis of volatile compounds obtained through solid phase microextraction/gas chromatography/mass spectrometry (SPME/GC/MS) with two sensory methods. RESULTS: Of the volatile compounds identified, 38 were analysed using a statistical multivariate approach and classified according to their role in the estimation of freshness during storage as markers of freshness or spoilage. Regarding the evolution of the presence or absence of individual compounds, three categories were defined. For example, the volatile compounds propanal, hexanal, 1‐penten‐3‐ol, pentanal, 2,3‐pentanedione, 1‐penten‐3‐one, heptanal, (E)‐2‐pentenal, 2,3‐octanedione, (Z)‐2‐penten‐1‐ol, 1‐pentanol, butanal, octanal, 3,5,5‐trimethyl‐2‐hexene, 1‐hexanol and 4,4‐dimethyl‐1,3‐dioxane appeared highly relevant, because they are found throughout storage and can be divided into several categories that are directly related to the quality of fish. CONCLUSION: SPME/GC/MS combined with a statistical multivariate approach may be a useful method to identify volatile compounds and characterise fish freshness during storage. Copyright © 2010 Society of Chemical Industry