Food Technology
Maryam Zamanian; Hassan Sadrnia; Mehdi Khojastehpour; Fereshteh Hosseini; Jules Thibault
Abstract
Introduction: Among the different types of polymers used for packaging and coating, polyvinyl alcohol (PVA), given its very enviable properties, has been used in various industrial applications. It is used for instance as controlled release in pharmaceutical elements, paper, textile and food supplement ...
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Introduction: Among the different types of polymers used for packaging and coating, polyvinyl alcohol (PVA), given its very enviable properties, has been used in various industrial applications. It is used for instance as controlled release in pharmaceutical elements, paper, textile and food supplement coating due to its good physical properties, chemical resistance, thermostability, film-forming capability, efficiency and biodegradability. The aim of this work was to examine the combined effect of montmorillonite (MMT) platelets and titanium oxide (TiO2) spherical nanoparticles on the physical and mechanical properties of PVA/ TiO2/MMT nanocomposites, and to determine the optimal combination to provide good properties, using response surface methodology (RSM). Materials & methods: PVA, PVA/TiO2, PVA/MMT and PVA/ TiO2/MMT nanocomposite films were prepared by the solution casting method. For each sample, 1.8 g of PVA was dissolved in 50 mL deionized water and maintained for 24 h at room temperature. The mixture was then heated to 90˚C and stirred using a magnetic stirrer up to 3 h to ensure the complete dissolution of PVA, followed by cooling down the solution to room temperature. Various amounts of TiO2 nanoparticles (1 and 2 w% on a dry basis) were added to deionized water and agitated with a stirrer for 12 h at 500 rpm. This method was also used for MMT (2 and 4 w% on a dry basis). The nanoparticle suspension was subjected to ultrasonic homogenization for 20 min to ensure a good dispersion. The 50 mL nanoparticle suspension was added to the PVA solution drop by drop during a period of 5 min while maintaining intense stirring (1000 rpm). Mixing was continued and glycerol (30 w% based on the polymer) was added. Vacuum with a rotary vacuum pump was applied to remove air bubbles from the solution. The solution was poured into a 15-cm internal diameter Petri dish with a perfectly flat bottom and carefully aligned horizontally. Homogeneous films were peeled off after drying in an air oven at 40˚C for 72 h. Scanning electron microscopy (SEM) and X-ray diffraction analysis (XRD) were performed for characterizing the morphology of nanocomposite films. The effect of these two nanoparticles on physical and mechanical properties, was evaluated by response surface methodology (RSM). A three-level factorial design was used to define the test points for the series of experiments. Among the various design alternatives suggested by theoretical algorithm, the selected design consisted of 13 experiments including five replicate central points used for variance calculation. Furthermore, PVA film data were analyzed using the Design-Expert program (Version 7.0, Stat-Ease Inc., Minneapolis, Minnesota) to find the optimum combination of constituents for the best properties. Results and discusions: X-ray diffraction patterns showed that the nanoparticles were well dispersed in the polymer matrix of PVA/ TiO2 and PVA / MMT films with layered microstructure. In addition, the linear effect of MMT nanoparticles and the interaction of TiO2 and MMT on tensile strength were significant. The linear, quadratic and interaction effects of both nanoparticles on Young's modulus were also significant. In general, the optimum values of TiO2 and MMT were 1% and 4% respectively for mechanical properties. The presence of both nanoparticles had a significant effect on transparency and ΔE. Results of nanocomposite films indicated that the film with 2% TiO2 and 4% MMT has higher WI and actually is darker than other samples. By analyzing different results with response surface method, the nanocomposite film with 0.5% TiO2 and 4% MMT was proposed as optimum combination for mechanical and physical properties
Omid Doosti Irani; Mahmood Reza Golzarian; Mohammad Hosein Aghkhani; Hassan Sadrnia
Abstract
Introduction: High percentage of orchard products, such as apples, is wasted due to mechanical damages that cause fruit quality loss. Damages due to static or dynamic pressure or impact are among very common mechanical damages that begin to bruise fruits. Post-harvest bruise damage is a major cause for ...
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Introduction: High percentage of orchard products, such as apples, is wasted due to mechanical damages that cause fruit quality loss. Damages due to static or dynamic pressure or impact are among very common mechanical damages that begin to bruise fruits. Post-harvest bruise damage is a major cause for the loss in fruit quality. Bruising means damaging fruit tissue and consequently physical changes resulting in fruit color and chemical changes resulting in fruit tastes (Xing and Baerdemaeker, 2005). Most research projects conducted on apple bruising have focused on the use of image processing techniques for detecting apple surface defects from images. In addition to images taken in visible spectral range, thermal images have been also used for this purpose. Having reviewed the literature and research gaps in this area, we set two hypotheses for this research project: first, the color characteristics of bruised tissue would change over time and these changes would be detectable on the images taken from the affected fruits. Second, there would be a significant difference between the surface temperature of bruised and sound tissues. The distribution of temperature on an impact-caused bruised tissue would change over time in a different manner compared with that for a sound tissue. The color and temperature variation is particularly related to the intensity of impact caused bruising and where the impact is applied on apples. Therefore, the first objective of this paper was to study the color changes on the tissues bruised from the impacts with three energy levels applied on three locations on apple surface with different curvatures: top, middle and bottom. The second objective was to investigate the temperature variation on the surface of the bruised apples and to examine the capability of visible and thermal imaging in detecting bruised tissues at different times after bruising occurred. Materials and Methods: For these purposes, the experiments were conducted on sixty apples of Golden Delicious variety. From sixty samples, five apples were used for determining apples ripeness index and five apples were used for determining emissivity factor which was used later in calibrating fruit surface temperatures on thermal images. Bruising was simulated by an impact pendulum. Bruising was conducted at three impact energy levels of 200, 700, 1200 mJ and applied at three locations on apple surfaces: top, middle and bottom. The samples affected by bruising-simulated impacting device were kept in a refrigerator at 5°C and were individually imaged in a regular basis until 624 hours after impact application. At the time of imaging, both visible and thermal images were taken from each sample. Samples visible images were taken in an imaging box with uniform controlled lighting. Thermal images were taken while samples were placed in a box that was thermally insulated from surrounding temperature. A newly defined color factor, named excessive yellow index (EYI) was extracted from visible color images. The EYI index formula is EYI = 1.5r+b-1.5g where r, g and b are red, green and blue color values, respectively. Factorial experiment was conducted for the assessment of EYI. This experimental design looked at the effects of three factors of time, impact energy and impact landing location on EYI. Result and discussion: The results showed that time passed after impact and the location of impact application had significant effect on EYI at 95% confidence interval. The apples EYI index decreased until 15 days after impact application and started increasing thereafter. Surface temperatures were extracted from the thermal images of samples. The results of processing thermal images showed that the bruised tissue was cooler than the sound tissue until 48 hours after impact application. Both tissues had the same temperature from 56 to 96 hours and then the bruised tissue started becoming warmer by 0.5-1°C after 96 hours. The color variation of bruised region was not detectable from visible images within the first 48 hours after impact application, while these regions were cooler than undamaged region and detectable from thermal images. The bruised regions started to turn dark brown at 48 hours after impact application. However, there was no temperature difference between bruised and sound regions on fruit surface for the period of 56-96 hours. The bruised brown regions paled after 360 hours. As a result, this reduced the capability of visible images for discriminating bruised apples from sound ones. Conclusion: The results of this research show that both the visible spectrum and thermal imaging systems can record the changes in color and temperature at different times after the bruising in apples. Therefore, these methods can be used as an efficient methods for grading apples.
Aliakbar Dadvar; Mehdi Khojastehpour; Hassan Sadrnia
Abstract
External and internal changes in fruits during storage time are affected by the various factors that some of them can by studied by measuring the qualitative parameters (physical and mechanical). The effects of storage time on some physical and mechanical properties of Valencia orange were investigated. ...
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External and internal changes in fruits during storage time are affected by the various factors that some of them can by studied by measuring the qualitative parameters (physical and mechanical). The effects of storage time on some physical and mechanical properties of Valencia orange were investigated. The experiment was performed as factorial based on completely randomized design. Analysis of experimental results showed a significant effect of storage time on all the physical parameters of Valencia orange. With increasing time, the true density of oranges increased while other physical parameters decreased. Rind ratio and moisture content increased and true density decreased with increasing the size of fruit. Also the effect of storage time and fruit size on the rupture force and deformation was significant at the level 0.01. The mean failure load for 2, 32 and 62 days storage were obtained 206.05, 139.64 and 221.07 N, respectively. Rupture force and deformation values were followed by increasing fruit size.
Saeideh Fayyazi; Mohammad Hossein Abaspour fard; Abbas Rohani; Hassan Sadrnia; Seyed Amir Hasan Monadjemi
Abstract
Due to variation in economic value of different varieties of rice, reports indicating the possibility of mixing different varieties on the market. Applying image processing and neural networks techniques to classify rice varieties is a method which can increase the accuracy of the classification process ...
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Due to variation in economic value of different varieties of rice, reports indicating the possibility of mixing different varieties on the market. Applying image processing and neural networks techniques to classify rice varieties is a method which can increase the accuracy of the classification process in real applications. In this study, several morphological features of rice seeds’ images were examined to evaluate their efficacy in identification of three Iranian rice varieties (Tarom (Mahali), Fajr, Shiroodi) in the mixed samples of these three varieties. On the whole, 666 images of rice seeds (222 images of each variety) were acquired at a stable illumination condition and totally, 17 morphological features were extracted from seed images. Fisher's coefficient (FC), Principal component analysis (PCA) methods and a combination of these two methods (FC-PCA) were employed to select and rank the most significant features for the classification. The so called LVQ4 (Learning Vector Quantization) neural network classifier was employed for classification using top selected features. The classification accuracy of 98.87, 100 and 100% for Fajr, Tarom and Shiroodi, 100 and 100% for Fajr and Shiroodi, 100 and 100% for Tarom and Shiroodi and 97.62 and 95.74% for Fajr and Tarom were obtained, respectively. These results indicate that image processing is a promising tool for identification and classification of different rice varieties.
