Mahyar Rad; Hamed Ghafori; Zohreh Gholami
Abstract
Introduction: Edible mushrooms are among the most perishable products that begin to lose quality immediately after harvest, and the short shelf-life of these products will cause problems when it comes to the marketing and distribution of these products in a fresh form. Edible coatings are a good tool ...
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Introduction: Edible mushrooms are among the most perishable products that begin to lose quality immediately after harvest, and the short shelf-life of these products will cause problems when it comes to the marketing and distribution of these products in a fresh form. Edible coatings are a good tool for prolonging the useful life of foods and increasing their quality without contaminating the environment. Materials and Methods: In this study, the possibility of increasing the shelf-life of a button mushroom using blanching followed by coating with carboxymethyl cellulose and sodium metabisulfite was studied. Independent variables included concentrations of carboxymethyl cellulose and sodium metabisulfite (0-2%) and storage time up to 16 days at 4 ° C. This experiment was designed on the basis of three-level factors consisting of 6 central points after 0, 4, 8 and 16 days of storage at 4°C. Factors determined on a button mushrooms included pH measurements, weight loss percentage, soluble solids, texture, color, browning level, total microorganisms count as well as mold and yeast count. Results & Discussion: The results of this study indicated that the sample coated with 2% carboxymethyl cellulose and 2% sodium metabisulfite resulted in an increase in pH level as well as soluble solids. In addition, the slightest color change, weight loss and reduction in tissue stiffness were observed in this sample. The sample coated with 2% carboxymethyl cellulose with 2% sodium metabisulfite had also the lowest total microorganisms count and the count of mold and yeast stored at 4 ° C after 16 days. Based on the results of this study, carboxymethyl cellulose and sodium metabisulfite coatings can be used as an appropriate coating agents for the preservation of organoleptic, chemical, microbial properties and shelf-life of button mushrooms.
Nasser Sedaghat; Sara Khoshnoudi
Abstract
Introduction : Pistachio (Pistaciavera L.) is a tasty nut and a good source of nutrients. Ithas a high content of numerous beneficial nutritive and bioactive compounds such as proteins, carbohydrate, moisture, vitamins, minerals, fiber and other micronutrients compounds, but the most exceptional components ...
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Introduction : Pistachio (Pistaciavera L.) is a tasty nut and a good source of nutrients. Ithas a high content of numerous beneficial nutritive and bioactive compounds such as proteins, carbohydrate, moisture, vitamins, minerals, fiber and other micronutrients compounds, but the most exceptional components are the amount of fats and especially unsaturated fatty acids. Therefore, this nut is highly susceptible to rancidity, especially after roasting. Despite the high quality, raw pistachio and pistachio processing industry at Iran, export of roasted and packaged pistachio, due to low shelf life and drastic changes intaste, is not very successfull. An effort was made to investigate the efficacy of gelatin in comparison with carboxymethyl cellulose (CMC) as edible coating to retard fat oxidation in roasted pistachio.Materials and methods:Five coating formulations were investigated in this study as follow: A) Gelatin (4% w/v) + ascorbic acid (1% w/v): TGA, B) CMC (1% w/v)+ ascorbic acid (1% w/v): “TCA”, C) ascorbic acid (1% w/v): “TA”, D) Gelatin (4% w/v) + CMC (1% w/v) + ascorbic acid (1% w/v): “TCGA” and 5) control sample (uncoated sample): “TCO”.Roasted pistachio nuts were coated by dipping the nuts in the coating solutions. For each treatment, 100 gram of pistachio nuts were packaged (BOPP/Al/CPP, 80 micron plastic bags) in triplicate. The physicochemical analysis included measurement of free fatty acid (FFA), peroxide value (meq.O2 kg-1),hardness (N), moisture (%) and the sensory evaluation (texture, rancidity, taste and overall acceptability) were performed on coated and uncoated pistachio nuts stored at 35 and 50 °C. The nuts were sampled on the 0th, 1st, 2nd and 3rd month of storage. Data was analyzed using Minitab 16. Analysis of variance (ANOVA) and general linear models (GLM) procedure wereused to compare the mean values of each treatment and Significant differences between the means of parameters were determined based on the results of the Tukey’s multiple range test (p0.05).FFA content of TCGA sample was significantly lower than other samples.The highest protection, according to these criterions, was provided by gelatin-CMC coating containing ascorbic acid.The control samples exhibited more bitterness and off flavor than the coated samples, seemingly on account of chemical reaction and second products of oxidation content. Instrumental and sensory hardness of pistachio nuts which were coated with gelatin and/ or CMC (TCA, TGA and TCGA) were significantly (p
Mahmood Reza Golzarian; Ali Mohammadzadeh; Mohammad Hossein Abaspour fard
Abstract
Introduction: Every year about 600 million tons of fruits and vegetables are produced in Asia and around 35% out of it is wasted during production, postharvest, processing, distribution and consumption (FAO, 2011). In most cases, the sale rate of agricultural products is affected by their internal quality. ...
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Introduction: Every year about 600 million tons of fruits and vegetables are produced in Asia and around 35% out of it is wasted during production, postharvest, processing, distribution and consumption (FAO, 2011). In most cases, the sale rate of agricultural products is affected by their internal quality. Although consumers are unable to detect product’s internal quality and freshness while buying, their negative perceptioncan be formed against their next buy if the internal quality of what they bought does not meet their satisfaction (Leemans et al., 2002). For assessing fruits quality factors some destructive and non-destructive tests are performed. The qualityfactors are categorized into external quality and internal quality factors. With the visual inspection methods, the external features of Bio-materials (e.g. shape, color and texture) can be evaluated (Shiranita et al., 1998) while the internal quality factors, including freshness, cannot be determined from these apparent visual characteristics (Jha et al., 2002). Therefore, the shelf life of agricultural products that are internally defective is less as they perish sooner and the infection expands quicker (Ohali, 2011). Among the common nondestructive methods for assessing internal quality parameters, MRI, X-RAY, Ultrasonic and NMR can be named (Du et al., 2004; Mery et al., 2011). In fruits, vegetables and fruits, the status of freshness is affected by the changes occurred in their physical, chemical and biological structures. These changes and, therefore, freshness, conventionally, is quantified by parameters such as product’s mechanical stress, moisture content, temperature and pH.Recently, some advanced technologies such as thermography have been used in quality assessment of agricultural products. Thermography is performed in two types: active and passive. In passive thermography, the heat emitted from the objects is recorded by the camera while in active thermography, which is more common in post-harvest applications, there is an external energy source to produce a thermal contrast between the sample product and the background. The objectives of this research areto use thermography in order to study the effects of time after harvest on the distribution of arils surface temperature and to relate the thermal properties to the freshness of arils.Materials and methods: Freshly harvested pomegranate fruits of Khazar variety were provided from Kashmar gardens. The arils were extracted from 35 randomly selected fruits. The arils of each fruit were kept for 15 days at 5°C. The arils were thermally and visibly imaged and their physical and mechanical properties were measured every 5 days: first day, fifth day, tenth day and fifteenth day after openingthe fruit to have variations in freshness. The size of thermals images was 320×240 pixels with the temperature resolution of 0.08°C. The images were taken with the emissivity set at 0.95, which was obtained from masking method (using a high-emissivitypatch). This emissivity value was within the range documented for biological products, i.e. 0.93-0.99 (Hellebrand et al., 2006). The thermal images were taken from the arils every 10 seconds for 180 seconds after imposing thermal shock by placing the arils in a freezer compartment at -2°C for 60 seconds. The distance from the thermal camera to the arils was 30cm and the room temperature was 22.5°C. The images were processed and analyzed in Matlab (MathworksInc, US) and the thermal features were extracted from the histogram of each thermal images, which included: mean temperature, variance, third moment, smoothness, homogeneity and entropy.Linear Discriminant Analysis (LAD) was employed for classification based on the mentioned features. The validity of input data was examined using Leave-one-out method. Statistical analysis was carried out using stepwise regression method in SPSS ver. 16.Results and discussion: The temperature extraction from the aril regions was done using the fusion of the segmented red/green ratio and the thermal image. The results showed that the temperature gradient with respect to time for one-day was the same as that for the five-day arils. This behavior was probably because the sound and fresh part of these arils was still large enough so that it causes less sensitivity with respect to the temperature change. However, the temperature gradient for ten-day and fifteen-day arils was relatively large. The analysis of temperature variations on arils surface showed that the less fresh the arils were,the more thermally sensitive they were with respect to their surroundings. The less fresh arils were cooler than the one-day and five-day arils. This might be due to the extended evaporation from the surface and the larger emissivity of older arils than fresher ones. The larger emissivity in less fresh tissues cause quicker heat penetration inwards or quicker heat loss from inside out, thus, the tissue become cool or hot quicker. Conversely, the fresh tissues have reduced heat transfer.They release heat in a cold environment or becomes warm it a warmer environment at a slow pace rate.The extracted temperature features were used in a Linear Discriminant Analysis (LDA) model for quality assessment and classification of pomegranate arils stored for three 60-second periods. The mean accuracy of classification of arils for three 60-second periods of imaging were obtained to be 62.1%, 72% and 79.8%. The optimum classification results were obtained from the third 60s. In this range, the accuracy of classification ofone-day, five-day, ten-day and fifteen-day arils were 98.7%, 69.23%, 65.4% and 89.8%, respectively. Conclusion: Twelve thermal features were extracted from thermal images of arils for classification in terms of freshness. The results confirm that thermography can be used as a non-destructive method for determining the freshness status of pomegranate arils during storage periods.
