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.     

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。     

Biogenic amines in selected foods of animal origin obtained from the Croatian retail market

ABSTRACT

This study aimed to investigate the presence of eight biogenic amines (BAs): tryptamine (TRP), phenylethylamine (PHE), putrescine (PUT), cadaverine (CAD), histamine (HIS), tyramine (TYR), spermidine (SPD) and spermine (SPM) in cheese, fish & fishery products and meat & meat products obtained from the Croatian retail market. A selective and robust method of high-performance liquid chromatography (HPLC) with diode array detection (DAD) was applied for the determination of BAs in a total of 91 samples in accordance with the performance criteria outlined in the European legislation. A high inter- and intra-food group variability of the amounts of BAs was observed. In the analysed samples, the most represented amines were TYR, HIS, CAD and PUT. Based on the highest content of the most toxic BAs (HIS and TYR) and consequential food safety concerns, the studied food groups can be ranked in the following order: cheese (HIS up to 106.4 mg/kg; TYR up to 206.6 mg/kg), fish &fishery products (HIS up to 98.8 mg/kg; TYR up to 47.9 mg/kg), and meat & meat products (HIS up to 20.0 mg/kg; TYR up to 117.5 mg/kg). The total BA content was significantly higher (p < .05) in fermented in comparison with other food. The study aimed to contribute to the knowledge on BA toxicity and food quality, as well as to support the indispensable future studies of consumption data and exposure assessment, to the end of defining allowable BA concentrations in food.     

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.     

Quantifying Total Viable Count in Pork Meat Using Combined Hyperspectral Imaging and Artificial Olfaction Techniques

Total viable count (TVC) of bacteria is one of the most important indexes in evaluation of quality and safety of meat. This study attempts to quantify the TVC content in pork by combining two nondestructive sensing tools of hyperspectral imaging (HSI) and artificial olfaction system based on the colorimetric sensor array. First, data were acquired using HSI system and colorimetric sensors array, respectively. Then, the individual characteristic variables were extracted from each sensor. Next, principal component analysis (PCA) was used to achieve data fusion based on these characteristic variables from two different sensor data for further multivariate analysis. In developing the models, linear (PLS and stepwise MLR) and nonlinear (BPANN and SVMR) pattern recognition methods were comparatively employed, and they were optimized by cross-validation. Compared with other models, the SVMR model achieved the best result, and the optimum results were achieved with the root mean square error of prediction (RMSEP)?=?2.9913 and the determination coefficient (R _p )?=?0.9055 in the prediction set. The overall results showed that it has the potential in nondestructive detection of TVC content in pork meat by integrating two nondestructive sensing tools of HSI and colorimetric sensors with SVMR pattern recognition tool.     

Evaluation of chicken freshness using a low-cost colorimetric sensor array with AdaBoost–OLDA classification algorithm

This paper attempted to evaluate chicken freshness using a low-cost colorimetric sensor array with the help of a classification algorithm. We fabricated a novel and low-cost colorimetric sensors array, with a specific colorific fingerprint to volatile compounds, using printing chemically responsive dyes on a C2 reverse silica-gel flat plate. In addition, we proposed a novel classification algorithm for sensors data classification – orthogonal linear discriminant analysis (OLDA) and adaptive boosting (AdaBoost) algorithm, namely AdaBoost–OLDA. And we compared it with two classical classification algorithms – linear discriminant analysis (LDA) and back propagation artificial neural network (BP-ANN). Experimental results showed classification results by AdaBoost–OLDA algorithm is superior to BP-ANN and LDA algorithms, the classification results by which are both 100% in the calibration and prediction sets. This study sufficiently demonstrated that the colorimetric sensors array with a classification algorithm has a high potential in evaluating chicken freshness, and AdaBoost–OLDA algorithm has a strong performance in solution to a complex data classification.     

Microbiological and physicochemical properties of dry‐cured neck inoculated with probiotic of Bifidobacterium animalis ssp. lactis BB‐12

The effect of inoculum level of Bifidobacterium animalis ssp. lactis BB‐12 probiotic strain and ripening period on the quality of dry‐cured neck was studied. The microbiological parameters (Enterobacteriaceae, LAB and TVC) and physicochemical attributes (pH value, a_w, TBARS index, colour) were determined directly after fermentation at 15 °C for 3 weeks, after 6 and 12 months of ripening at 4 °C. The highest LAB count and a lower pH value were found in the meat inoculated with probiotic strain at 6.6 log cfu g^?1 (B2) followed by inoculation with probiotic strain at 6.3 log cfu g^?1 (B1). Level of inoculation had not had an influence on water activity, TBARS index and total colour parameters. Changes of fat oxidation during half‐year of ripening were limited in probiotic meat samples compared to naturally fermented control meat (C). Based on the results, it can be concluded that the most favourable physicochemical and microbiological parameters of the dry‐cured neck were obtained after 6 months of ripening. At that time, the Bifidobacterium BB‐12 at both levels is a good potential starter for meat fermentation.     

Hypoxanthine-based enzymatic sensor for determination of pork meat freshness

An enzyme sensor employing xanthine oxidase (XO), soluble or immobilised, in combination of an oxygen electrode has been developed and optimised to determinate the hypoxanthine (Hx) content in pork meat at different post-mortem times as measure of meat freshness. The amperometric signal obtained due to the oxygen depletion during the Hx oxidation was related with the consumed oxygen at 190 s in the soluble enzyme sensor or enzymatic rate at 10 s in the immobilised enzyme sensor. In both cases a linear relationship between the signal and the Hx concentration in the range 8.68–26.05 μM (R² = 0.999) and 15.63–127 μM. (R² = 0.995), respectively, was found. Both enzyme sensors exhibited very good working conditions and storage stability. A study of Hx oxidation was carried out in order to compare the Hx content measured by both sensors and those measured by high performance liquid chromatography (HPLC) obtaining a good agreement between both techniques. Therefore, the easy preparation and operation of both enzyme sensors suggests a reliable, rapid and an economical alternative for simple or multiple Hx measurements constituting a useful tool as quality control of meat freshness.     

Effect of dietary supplementation with vitamin E on characteristics of vacuum‐packed lamb

The effect of dietary vitamin E supplementation on lamb during vacuum‐packed storage was studied. Thirty‐six weaned male Manchego breed lambs were offered four dietary treatments (20, 270, 520 and 1020 mg vitamin E kg^?1 feed). Lambs were fed the vitamin E‐supplemented diet from 13 until 26 kg live weight. Pieces of M. longissimus dorsi were stored under vacuum at 2 ± 1 °C in the dark and meat quality was assessed after 5, 14 and 28 days of storage. Dietary supplementation significantly increased the α‐tocopherol concentration in the muscle (P < 0.001). Initially, lipid oxidation, meat colour and bacterial load were similar in all groups. In meat of non‐supplemented lambs the thiobarbituric acid reactive substance value increased throughout storage, whereas in meat of supplemented lambs it did not increase. Meat pigments and discolouration proportion were significantly affected by storage time (P < 0.001). The bacterial load was low initially, but after 28 days of storage it was close to 7 log₁₀ colony‐forming units (cfu) cm^?2 and Enterobacteriaceae surpassed the limit of acceptability of 2.5 log₁₀ cfu cm^?2, making the lamb unsuitable for human consumption. Meat of supplemented lambs displayed less lipid oxidation than that of their non‐supplemented counterparts, while meat colour and bacterial load were not affected by supplementation. Copyright © 2007 Society of Chemical Industry     

Rapid and non‐invasive evaluation of pork meat quality during storage via impedance measurement

In this study, the evolutions of impedance and bio‐indicators (total aerobic count (TAC), total volatile base nitrogen (TVB‐N) and pH) of meat freshness during storage at 4 °C were investigated and compared. The influence of electrode configurations, frequencies and directions of applied electric fields on impedance measurement was considered. Good relationships between measured impedance and bio‐indicators were obtained, with R² ranging from 0.758 to 0.992, RMSE from 0.11 to 0.57 for TAC and R² ranging from 0.636 to 0.989, RMSE from 0.29 to 1.68 for TVB‐N. Bar and ring electrodes had better performance as compared to needle electrodes. Effects of frequency on impedance were important from 20 Hz to 200 kHz and diminished in the higher ranges. Impedance generally exhibited better correlations with TAC, TVB‐N at high frequency than at low frequency. The findings demonstrated that impedance measurement could be a viable, rapid method to assess the quality of stored pork meat.     

Application of multi‐element viscoelastic models to freshness evaluation of beef based on the viscoelasticity principle

The aims of this work were to develop multi‐element viscoelastic models for beef and apply them to detect total volatile basic nitrogen (TVB‐N) content for freshness evaluation. The deformation data were collected by a viscoelasticity detection system that employed the airflow and laser technique. Then, TVB‐N contents were measured to determine the freshness of samples during storage. A universal global optimization (UGO) algorithm was applied to fit the deformation data. Various multi‐element viscoelastic models including the Burgers, six‐element and eight‐element models were built using the obtained fitting parameters, and different viscoelastic parameters representing the degree of beef spoilage were obtained. All the viscoelastic parameters of each multi‐element model and parameter combinations of the selected six‐element model were employed to build mathematical models for predicting TVB‐N content by support vector machine regression (SVR). In comparison, the six‐element model with all the viscoelastic parameters performed the best and was determined to predict TVB‐N content with correlation coefficient in the prediction set (R_P) of 0.891 and root mean squared error in the prediction set (RMSEP) of 1.467 mg/100 g. Based on the results of parameter combinations, combination (E₂, E₃, E₁, η₁, η₂) from the six‐element model performed the best, which was comparatively inferior to all the viscoelastic parameters of the six‐element model. Results demonstrated that it was possible to predict TVB‐N content for freshness evaluation by applying method of developing multi‐element model based on the viscoelasticity with chemometrics.     

Impact of UV‐C Light on the Fatty Acid Profile and Oxidative Stability of Nile Tilapia (Oreochromis niloticus) Fillets

The influence of different ultraviolet (UV‐C) doses (0.103 and 0.305 J/cm²) was investigated by instrumental color parameters, pH, lipid, and protein oxidations, fatty acids (FA) composition and biogenic amines (BAs) in Nile tilapia fillets during 11 d at 4 ± 1 °C. The UV‐C treatment increased (P < 0.05) a^* values and protein oxidation in a dose‐dependent manner, and delayed (P < 0.05) the formation of BAs over the course of the storage period. L^* values and lipid oxidation were not influenced (P > 0.05) by UV‐C light. Fillets treated with a low UV‐C dose exhibited greater (P < 0.05) total polyunsaturated fatty acid (PUFA) than their untreated counterparts. Therefore, a low UV‐C dose can be recommended in tilapia fillets as an alternative processing method to control pH and BAs, as well as improve the total PUFA amount and overall nutritional quality.     

Effect of Filling Type and Heating Method on Prevalence of Listeria species and Listeria monocytogenes in Dumplings Produced in Poland

The count of Listeria monocytogenes was determined, before and after heat treatment, in 200 samples of dumplings of 9 brands and with different types of stuffing. Analyses were conducted according to ISO 11290–1 standard and with real‐time PCR method. The highest count of L. monocytogenes was found in meat dumplings (10² to 10⁴ CFU/g), whereas products with white cheese‐potato stuffing and vegetable‐mushroom stuffing contained significantly less Listeria, 20 to 80 and 5 to 32 CFU/g, respectively. In cooled meat dumplings the extent of contamination depended significantly on the producer. In addition, a significant (P < 0.05) correlation was determined between contamination level and meat content in the stuffing (rho = 0.418), especially in stuffing containing pork meat (0.464), contrary to beef‐containing stuffing (0.284). Heating dumplings in boiling water for 2 min completely eliminated L. monocytogenes in meat dumplings. In contrast, the microwave heating applied for 2 min at 600 W only reduced the count of L. monocytogenes by 1 to 2 logs. Hence, the microwave heating failed to reduce the risk of infection with this pathogen below the level permissible in the EU regulation, especially in the most contaminated samples. In this case, the efficacy of microwave heating was significantly (P < 0.05) affected by the initial count of L. monocytogenes (rho = 0.626), then by meat content in the stuffing (0.476), and to the lowest extent—by the type of meat (0.415 to 0.425). However, no Listeria sp. and L. monocytogenes were isolated from cooked dumplings with fruits (strawberries or blueberries).     

Colorimetric sensor arrays based on chemo-responsive dyes for food odor visualization

BackgroundThe colorimetric sensor array technology simulates human olfaction to analyze, identify and examine complex gas and volatility based on chem-responsive dyes. Unlike human olfaction and electronic noses, colorimetric sensor array is more objective and not susceptible to interference. In additional, with the visualization, rapidity and non-destruction of analysis, colorimetric sensor array has been increasingly applied in food science and industry.Scope and approachThis review focuses on the colorimetric sensor array technology and its major applications in food industry. Technical considerations associated with the chemo-responsive dyes, substrate materials, and data processing methods are discussed. In application, any type of food samples including solid, liquid food samples could be directly analyzed using colorimetric sensor array. Additionally, the recent development, and future research trends are also involved.Key findings and conclusionsThe colorimetric sensor array technology offers an exciting method to establish the correlation between the output of a colorimetric sensor array and the odor components, thereby enabling visual quantification of odors. It provides a potential odor-image-based monitoring tool for the rapid, reliable and in-line assessment of food safety and quality.     

Effect of ionic strength on inactivation kinetics of Escherichia coli O157:H7 by electron beam in ground beef, chicken breast meat, and trout fillets

The ionic strengths (IS) of ground beef, chicken meat, and trout fillets were modified to intermediate and highest with 3.5% and 7.0% NaCl, respectively. The samples with modified and unaltered (native) IS were inoculated with Escherichia coli O157:H7 and subjected to electron beam (e‐beam). The water activity (a_w) of the meat samples were 1.0, 0.96–0.97, and 0.94 for native, intermediate, and highest IS. The D₁₀‐values were calculated from survivor curves. The D₁₀‐values for E. coli ranged from 0.19 kGy in trout (highest IS) to 0.31 kGy in beef and chicken (highest IS). Regardless of the meat type, the increased resistance of E. coli to e‐beam was only observed at the highest IS. The difference of the D₁₀‐value for E. coli in samples at intermediate and native IS was insignificant. Regardless of the IS, the E. coli in trout was most sensitive, while the difference of E. coli resistance to e‐beam in ground beef and chicken meat was insignificant.     

A Potential Use of 3‐D Scanning to Evaluate the Chemical Composition of Pork Meat

The aim of this study was to determine the possibility of 3‐D scanning method in chemical composition evaluation of pork meat. The sampling material comprised neck muscles (1000 g each) obtained from 20 pork carcasses. The volumetric estimation process of the elements was conducted on the basis of point cloud collected using 3‐D scanner. Knowing the weight of neck muscles, their density was calculated which was subsequently correlated with the content of basic chemical components of the pork meat (water, protein and fat content, determined by standard methods). The significant correlations (P ≤ 0.05) between meat density and water (r = 0.5213), protein (r = 0.5887), and fat (r = ?0.6601) content were obtained. Based on the obtained results it seems likely to employ the 3‐D scanning method to compute the meat chemical composition.     

Change of volatile compounds in fresh fish meat during ice storage

Abstract: The change of volatile compounds in fresh fish meat during 3‐ to 4‐d ice storage was investigated for several fishes using an electronic nose system and a gas chromatography‐mass spectrometer (GC/MS) with headspace solid‐phase micro‐extraction (SPME). Principal component analyses for samples using the electronic nose system revealed that the increase of some volatile compounds during storage was rapid in sardine (Sardinops melanostictus), jack mackerel (Trachurus japonicus), and chub mackerel (Scomber japonicus); moderate in yellowtail (Seriola quinqueradiata), skipjack (Katsuwonus pelamis), and young oriental bluefin tuna (Thunnus thynnus). In contrast to these fishes, the change was little in “white meat” fishes such as red seabream (Chrysophrys major), Japanese seabass (Lateolabrax japonicus), flatfish (Paralichthys olivaceus), puffer (Lagocephalus wheeleri), and bartail flathead (Platycephalus indicus). SPME‐GC/MS analysis showed that some aldehydes and alcohols such as 1‐heptanol, (E)‐2‐octenal, (E)‐2‐hexenal, 1‐pentanol, (E,E)‐2,4‐heptadienal,2,4‐hexadienal, 1‐hexanol, 4‐heptenal, and so forth increased rapidly in jack mackerel and chub mackerel, slowly in skipjack, and a little in red seabream and puffer during the storage. The increase of these compounds was considered to have an effect on the change of electronic nose response. Hexanal was a dominant compound increased from the beginning of the storage in jack mackerel. The increase of volatile compounds was little in red seabream and puffer. The increase of these aldehydes and alcohols was thought to be an appropriate marker for monitoring the freshness of “fresh” fish except for white meat fish. Practical Application: The results of this study are ready to apply for preventing fishy off‐flavor of fisheries products. Lipid oxidative derivatives other than trimethylamine contributed to fresh fish flavor; therefore, to prevent lipid oxidation seemed important.     

溴麝香草酚蓝/玉米醇溶蛋白指示标签对金枪鱼新鲜度的监测

近年来,智能检测食品新鲜度的比色膜受到越来越多的关注。本实验利用静电纺丝技术研制出一种溴麝香草酚蓝（bromothymol blue,BTB）/玉米醇溶蛋白（zein,ZN）新型智能比色标签,用于金枪鱼鱼片的新鲜度监测。BTB在pH值为5～12时的明显颜色变化赋予了指示标签灵敏的pH值传感效果。通过场发射扫描电子显微镜、傅里叶变换红外光谱、X射线衍射、差示扫描量热仪对不同BTB添加量的BTB/ZN指示标签的形貌和结构进行表征。再将BTB/ZN指示标签应用于金枪鱼鱼片新鲜度的指示验证实验,对指示标签的指示效果进行验证。结果表明,BTB/ZN指示标签的微观结构良好,BTB可以很好地与ZN结合在一起,并且不破坏二者的结构;质量分数4% BTB的BTB/ZN指示标签的指示效果最佳,能灵敏地反映金枪鱼的新鲜度变化。指示标签的色度和金枪鱼鱼肉的总挥发性盐基氮含量之间存在显著相关性,这证明BTB/ZN指示标签能有效监测金枪鱼鱼片的新鲜度。     

Characterization of the Residual Pink Color in Cooked Turkey Breast and Pork Loin

The residual redness was characterized in well cooked meat from turkey breast and pork loin. A simple method of scanning thin slices by transmission spectrophotometry was used to evaluate the meat pigments in situ. Absorption bands at 414, 520, and 550 nm of the spectra obtained from cooked meat led to the conclusion that residual pink color was caused by cytochrome c. The method was further modified to study the effect of air contact on meat color after cooking. Other pigments were spontaneously oxidized as soon as meat surface was exposed to air. The concentrations of hemoproteins in turkey and pork were determined and found to be related to cooked meat color.