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Aflatoxin B1 is a type of mycotoxin produced by Aspergillus fungi during food production and storage. Aflatoxins have many toxic effects on the body that cause mutagens, teratogens and have high carcinogenic properties that cause cancer in the liver and other organs. Although conventional device methods for measuring aflatoxin B1 in food are sensitive and accurate, they have disadvantages such as high diagnostic time, high cost, the need for a trained user, and the creation of false positive results. Therefore, the development of new measuring methods has been prioritized by researchers. Among these measurement methods is the use of biosensors, which are fast, simple and more affordable and are used in the food industry today. In this work, a colorimetric optical aptasensor using gold nanoparticles with appropriate sensitivity and high selectivity was used to detect aflatoxin B1 in serum and buffer. For this purpose, gold nanoparticles were synthesized by reducing HAuCl₄ by sodium citrate (with a size of 14.40 nm and a zeta potential of -27.5). In this method, the protective effect of DNA sequence on the surface of gold nanoparticles has been used in the presence or absence of aflatoxin with the intervention of salt and the characteristic of visual color change. The detection limit of this method was estimated to be 50 ng/L and its linear range was 200-28000 ng/L. As a result, the designed aptasensor can be used for quick identification and screening of this toxin in contaminated food.
 

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The formation of chitosan nanoparticles (CSNPs) with a high stability still remains a main challenge in terms of applying the produced particles in the field of nutraceutical and drug delivery systems. Giving that there are many variables parameters which could affect the size, morphology, and other properties of fabricated CSNPs during ionic gelation process along with using sodium tripolyphosphate (STPP) as the most common cross-linking agent. In this study, after the production of CSNPs under the influence of various independent variables such as chitosan (CS) concentration, STPP concentration, and CS to STPP ratio, in the next step, the physical, rheological, turbidity, and colorimetric properties of the produced nanoparticles were measured. Finally, two artificial neural networks (ANNs) – multilayer perceptron (MLP) and radial basis function (RBF) – with a single hidden layer and different threshold functions, learning algorithms, etc. were employed to predict the CSNPs properties. The results revealed that MLP for the physical, viscosity, b^*, and chroma properties and RBF for other properties – with a Levenberg-Marquardt (LM) learning algorithm of 1000 epochs – well predict them with a very high determination coefficients (R²) and low mean square error (MSE). R² for nanoparticle size, poly dispersity index (PDI), zeta potential, viscosity, and electrical conductivity of CSNPs suspensions were determined 0.9881, 0.9534, 0.9431, 0.9212, and 0.9636, respectively. However, RBF with a single hidden layer comprising a set of 3 inputs, 4 neurons in hidden layer, and 3 outputs with the SigmoidAxon- SigmoidAxon transfer function presented the best results for predicting the L^*, ΔE, and WI properties of CSNPs suspensions. In addition, R² for L^*, ΔE, and WI of CSNPs were calculated 0.9586, 0.9775, and 0.9457, respectively. Also, the flow behavior index of CSNPs suspensions was determined less than 1, which indicates the pseudoplastic behavior of the samples.

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In this study, natural dye curcumin wasused to monitor the quality of packaged fish meat through color changing indicators and the color changes of the indicators were evaluated visually and with colorimeter during storage of fish samples at room temperature (for 60 hours) and in the refrigerator (for 12 days). In order to evaluate performance of paper indicators for monitoring the quality of fish, the quality characteristics of fish such as total viable count, pH, and TVB-N were evaluated. This indicator had very good characteristics such as less moisture absorption than the control, excellent stability during storage for 30 days, and high selectivity to pH changes. The FTIR results showed that the curcumin was well stabilized on cellulose filter paper. The results of color changes of the indicator during fish storage indicated that with increasing the storage time, the brightness (L *) of the indicator based on curcumin significantly decreased and red-green (a *) and yellow - Blue (b *) parameters increased. Colorimetric indicator based on curcumin indicated significant color changes from yellow to orange due to sensitivity to pH and detection of TVB-N and hydrogen sulfide compounds. According to the results obtained from the qualitative characteristics of fish in relation to performance and function of colorimetric indicator during fish spoilage, it can be concluded that curcumin provides a promising approach in intelligent packaging systems for meat products to monitor fish meat freshness.

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Today, the utilization of smart indicators in food packaging to monitor and detect food quality through analyzing quality data and color changes in packaging films based on the food's condition is on the rise. In this comparative study, halochromic films made of gelatin and k-carrageenan with mirabilis jalapa extract (6, 12, and 24%) and barberry extract (6, 12, and 24%) were developed and examined. Through SEM images and FTIR spectroscopy, it was observed that both types of films incorporating barberry and mirabilis jalapa extracts were uniformly dispersed in the gelatin and k-carrageenan polymer matrix, displaying notable molecular interactions like hydrogen bonding and electrostatic forces. However, films containing mirabilis jalapa extract exhibited more irregular and rough surfaces compared to those with barberry extract. Both types of films displayed good antioxidant properties and responsiveness to changes in pH and ammonia levels. Films with barberry extract demonstrated higher antioxidant activity and greater sensitivity to pH variations. The gelatin and k-carrageenan films with barberry and mirabilis jalapa extracts effectively indicated the freshness of lamb meat stored at 25°C by correlating with the presence of ammonia gases in the storage packages and pH fluctuations. Our results highlight that the structural, physical, and functional attributes of gelatin and k-carrageenan films incorporating pH-responsive extracts are significantly influenced by the extract type and concentration.
 

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Original Walkley-Black (OWB) method has been extensively used for measuring Soil Organic Carbon (SOC), mainly because of its convenience. However, the reliability of this method is still under speculation. In recent years, Permanganate Oxidizable Carbon (POXC) has been suggested to be more useful than the total SOC. In the present study, SOC contents of the 20 non-calcareous soil samples (0-20 cm) were determined by the OWB method and its modified versions (WB with external heating and WB using colorimetric determination) to understand their relationships with easy-to-find Soil Organic Matter (SOM) determined by the method of Loss-On-Ignition (LOI) at two temperatures (400 and 550°C). The POXC was also determined in the sampled soils and applicable relationships were specified between these methods. Eight of the 20 soils were selected to determine the accuracy of different WB methods using total organic carbon by CHN elemental analysis. Results showed strong power relationships between LOI and OWB methods. The WB method with external heating exhibited the highest recovery (95.3%) among the tested methods. This could be attributed to the finer soil particles used in the proposed method (less than 0.15 mm) than what has been used in the conventional method (less than 0.5 mm). The POXC method showed a high correlation with OWB method and, on average, accounted for only 4.1% of the Total Organic Carbon (TOC). This would likely reduce the value of POXC as an independent parameter to derive the labile fraction of SOC.