Food Engineering
Fakhreddin Salehi; Moein Inanloodoghouz; Sara Ghazvineh; Parisa Moradkhani
Abstract
IntroductionSour cherries (Prunus cerasus L.) are relatively diverse and broadly distributed around the world, being found in Asia, Europe, and North America. Sour cherries have unique anthocyanin content, and rich in phenolic compounds. The fruits are generally used for processing purposes, such as ...
Read More
IntroductionSour cherries (Prunus cerasus L.) are relatively diverse and broadly distributed around the world, being found in Asia, Europe, and North America. Sour cherries have unique anthocyanin content, and rich in phenolic compounds. The fruits are generally used for processing purposes, such as for production juice and jam. The fruits of sour cherries can also be frozen and dried. One of the best methods for the preservation of agricultural product is drying, which involves removing water from the manufactured goods. Dried sour cherries have a long shelf life and therefore may be a fine alternative to fresh fruit all year round. There are no reports on the effect of microwave pretreatment on the hot air drying kinetics of sour cherries in the literature. Hence, the purpose of this study was to estimate the impacts of microwave pretreatment on the total phenolics, drying time, mass transfer kinetic, effective moisture diffusivity, total color difference index, shrinkage and rehydration of sour cherry. In addition, the moisture ratio changes of sour cherry during drying were modeled. Material and MethodsSour cherries were purchased from the market at Bahar, Hamedan Province, Iran. The average diameter of fresh sour cherries was 1.6 cm. In this study, the water content of fresh and dried sour cherries was calculated using an oven at 103°C for 5 h (Shimaz, Iran). In this research, the effect of microwave time on the drying time, effective moisture diffusivity coefficient and rehydration of sour cherries was investigated and drying kinetics were modeled. To apply the microwave pretreatment on the sour cherries, a microwave oven (Gplus, Model; GMW-M425S.MIS00, Goldiran Industries Co., Iran) was used under atmospheric pressure. In this work, the influence of the microwave pretreatment time at five levels of 0, 30, 60, 90, and 120 s (power=220W) on the cherries was examined. After taking out the treated sour cherries from microwave device, the samples were placed in the hot-air dryer (70°C) as a thin layers. The dehydration kinetics of sour cherries were explained using 7 simplified drying equations. Fick's second law of diffusion using spherical coordinates was used to calculate the moisture diffusivity of sour cherries at various hot-air drying conditions. The rehydration test was conducted with a water bath (R.J42, Pars Azma Co., Iran). Dried sour cherries were weighed and immersed for 30 min in distilled water in a 250 ml glass beaker at 50°C. Results and DiscussionThe results showed that microwave treatment led to an increase in moisture removal rate from the sour cherries, an increase in the effective moisture diffusivity coefficient, and, consequently, a decrease in drying time. By increasing the microwave time from 0 to 12 s, the average drying time of sour cherries in the hot-air dryer was decreased from 370 min to 250 min (p<0.05). The average effective moisture diffusivity coefficient calculated for the samples placed in the hot-air dryer was 4.25×10-10 m2/s. Increasing the microwave time from 0 to 120 s increased the average effective moisture diffusivity coefficient by 85%. The maximum amount of phenolic was related to the sample treated with microwave for 90 seconds. Microwave treatment time had no significant effect on the rehydration of dried sour cherries. ConclusionKinetic modeling of weight changes of sour cherries during drying was carried out using models in the sources, followed the Page model was selected as the best model to predict moisture ratio changes under the selected experimental conditions. The mean values of sum of squares due to error, root mean square error, and r for all samples ranged from 0.001 to 0.007, 0.005 to 0.017, and 0.997 to 0.999, respectively. Generally, 120 s pre-treatment by microwave is the best condition for drying sour cherries.
Food Engineering
Javad Safari; Jafar Hashemi; Azadeh Ranjbar Nedamani
Abstract
Introduction Due to the importance of product appearance quality in product grading and the impact of factors such as area, uniformity, and various defects on the product quality, and also, the ability to recognize these features at a very low cost, image processing techniques, is one of the methods ...
Read More
Introduction Due to the importance of product appearance quality in product grading and the impact of factors such as area, uniformity, and various defects on the product quality, and also, the ability to recognize these features at a very low cost, image processing techniques, is one of the methods used to evaluate food quality. Therefore, in this study, a non-destructive image processing method was used to investigate the factors affecting the color and shrinkage of apple slices during drying. Materials and Methods Golden delicious apples were used in this research. The central part of the apple (including the rivet, seeds, and tail) was removed by a kernel separator and sliced into 3, 5, and 7mm thickness and approximately 7 mm diameter slices using a hand slicer without separating the skin. Three temperatures of 60, 70, and 80 °C were used to dry the samples. To determine the moisture content of a sliced apple, the samples were first weighed on a digital scale, then placed in a dryer, and the experiment was continued until the samples reached equilibrium mass. Due to the high importance of moisture ratio in controlling the drying process, moisture rate (MR) and moisture content (MC) were calculated, and samples were taken to investigate the amount of surface shrinkage, general color changes and browning index. After extracting L*, a*, and b* values, total color changes and browning index (to show the intensity of brown color in the product) for all samples before and after drying were calculated and evaluated to describe color changes after drying. Results and Discussion The drying kinetics results showed that the drying process significantly depends on the thickness of the samples. According to drying curves, at the early stages of drying, the decrease in humidity occurs more severely and the graph has a steeper slope, but as the process continues and the moisture content of the product decreases, the slope of the curve decreases. In the early stages of drying, due to the presence of water inside the fresh fruit cells, there is a pressure balance between the fruit and the surrounding environment, which causes the fruit to remain swollen. However, as the drying time progressed, contractile stresses are created, which cause superficial shrinkage. In this study, it was observed that increasing the thickness from 3mm to 7mm, reduced the final shrinkage on the surface of apple slices by 11% at 60 °C, 12% at 70 °C, and 13% at 80 °C. After moisture leaves the surface of the product and heat penetrates into the product, moisture begins to leave the product by conducting interstitial convection. When moisture moves to the surface, the mechanical balance and consequently the textural structure of the sample is disturbed due to the creation of different spaces in thickness. According to the results, increasing drying time and thus decreasing the moisture content, increases the percentage of apple shrinkage. On the other hand, at a certain thickness, with increasing temperature, the percentage of shrinkage changes in the thickness of the product decreases. Therefore, at thicknesses of 3, 5, and 7 mm, the increase in temperature from 60°C to 80°C, decreased the amount of shrinkage thickness by 16, 12, and 8%, respectively. It is in higher thicknesses that react with heat and change the color of the fruit due to the Maillard reaction. After complete drying of apple samples, the highest amount of color change was related to the thickness of 7 mm and a temperature of 80°C, which was equal to 1.254. Also, the lowest rate of discoloration of apple slices in a thickness of 3 mm and a temperature of 60 °C was 0.889. The browning index (Bi) in the high thickness of apple slices is less affected by the process temperature due to the increase in moisture level. For this reason, the rate of browning was very low among the experimental samples and the highest rate of browning was related to the thickness of 7 mm and the temperature of 80 °C was 585/2559. Also, the lowest rate of browning of apple slices was observed in the thickness of 3 mm and the temperature of 60 °C was 584.254. Conclusion Finally, it was found that the thickness and temperature factors can have an effect on the quality of product during drying process. The results of this study can provide a cheap and fast way to control the quality of fruits during drying and help producers of these products select the main process factors that affect the final quality.
Food Engineering
Hadi Samimi Akhijahani
Abstract
Introduction: Drying of agricultural products is one of the main ways to prevent product spoilage. There are several methods to dry agricultural products, including direct sunlight, hot, sunny weather, microwave, vacuum, and freezer which use different energy sources. Due to constrain of fossil ...
Read More
Introduction: Drying of agricultural products is one of the main ways to prevent product spoilage. There are several methods to dry agricultural products, including direct sunlight, hot, sunny weather, microwave, vacuum, and freezer which use different energy sources. Due to constrain of fossil fuels supply, the price of this type of energy is increasing thus the tendency to use renewable energies is increasing (Purohit and Kandapal, 2005; Purohit et al., 2006). In Iran the drying efficiency of solar dryers is low because less solar energy is converted into thermal energy. Therefore, many measures have been taken to increase the efficiency of solar collectors which causes to obtain the dried samples with better quality and lower cost. In this study a combination of tracking system and phase change materials (PCM) are used to increase the efficiency of solar dryer cabinet with three types of collectors including flat plat (FPC), parabolic trough (PTSC) and evacuated tube (ETSC) collectors. Materials and Methods: The dryers used in this study include a cabinet connected to a flat plat, parabolic trough and evacuated tube collectors. In all of the dryers, PCM have been used to maximize solar energy utilization. Moreover to get the maximum solar radiation the tracking system used in FPC and PTSC and a storage tank with fluid pump used in PTSC and ETSC. The air flow rate inside the system was about 0.018 kg.s-1 for all the experiments. The experiments were performed in three continues days from 16 to 18 June 2018, from 8:00 to 24:00. Tomato sample with a thickness of 9 mm was considered for drying process. To describe the drying process of the samples, the moisture ratio versus time was considered. Also, the drying efficiency was defined considering the ratio of energy (thermal and mechanical) consumed to heat the product and extract moisture from the product (Qm) to the total energy used for drying process, including fluid thermal energy (Qf) and mechanical energy (Emec) (Fudholi et al., 2014). In order to evaluate the quality of the dried product at different modes, three quality parameters including color difference, shrinkage and rehydration ratio were considered. Color difference between the fresh and dried samples was evaluated as one of the most important factors that the customer was considered for selection (Magdic et al., 2009). The change in the volume of the dried product compared to the fresh product is defined as shrinkage. Moreover, to evaluate the rehydration ratio the weight of water absorbed by the samples was considered. Results and Discussion: The effect of variations of the intensity of solar radiation on the amount of solar energy taken by the collectors was negligible. The time required to dry tomato slices by the dryer equipped with FPC was longer than the other systems. The results also showed that the highest drying efficiency is related to the dryer with ETSC and it was about 39.02%. The least value is related to the dryer with FPC and it was about 30.12%. Due to the long drying time the use of the fan and the pump increase and the amount of energy consumed to drying the product increases as well. Thus the efficiency of the dryer with FPC decreases. The values of specific energy for the dryer with FPC, PTSC and ETSC were obtained as 7.12, 7.92 and 8.34 MJ/kg, respectively. The results of qualitative evaluation of dried tomato slices showed that the product obtained from the dryer equipped with ETSC, due to the short drying time, the color changes and the shrinkage was suitable in comparison with the other reports. The amount of rehydration ration was the highest as well. Using PCM had no adverse effect on the quality of the dried samples. The results showed that the dryer with ETSC had higher efficiency (about 39.02%) and the quality of the samples was suitable compared to other systems. Using recycling system can improve the thermal efficiency of the solar dryer.
Ali Shahdadi Sardoo; Nasser Sedaghat; Masoud Taghizadeh; Elnaz Milani
Abstract
Introduction: In Iran, the main problem in greenhouse cucumber production and post-harvest shelf life is short due to the application of traditional packaging and storage methods. This research was carried out in order to investigate on the effects of packaging type and chitosan edible coating on the ...
Read More
Introduction: In Iran, the main problem in greenhouse cucumber production and post-harvest shelf life is short due to the application of traditional packaging and storage methods. This research was carried out in order to investigate on the effects of packaging type and chitosan edible coating on the physicochemical and sensory characteristics of Royal Greenhouse cucumber during storage conditions, in order to prevent of Royal greenhouse cucumber postharvest losses.
Materials and methods: Royal greenhouse cucumbers placed inside the three-layer plastic bags of PE/PA/PE and the effect of different chitosan coating (0, 0.5 & 1 %), concentration of oxygen (3,12 & 21%), storage temperatures (5, 15 & 25 ˚C) and storage time (3, 12 & 21 days) on cucumber quality and shelf life was studied. The quality of cucumber samples was evaluated by weight loss, firmness retention, surface color development (L*, a*, b*), shrinkage and sensory evaluation (taste and freshness).
Results and discussion: The obtained results showed that firmness and organoleptic properties decreased with increasing temperature and time storage, while weight loss and shrinkage was increased, that Leading to loss of cucumber samples quality during storage. Increasing of chitosan coating to 0.5% also showed a beneficial effect on physicochemical and sensory characteristics of the samples during the storage time compared to the control fruit, but by increasing it to 1%, decreased the quality of the final product. The results showed that using modified atmosphere packaging and storage at low temperatures can be in addition to the slow breathing fresh cucumbers from softening and prevent moisture loss the maintenance of cucumber. MAP packaging leads to keeping cucumber green and quality properties compared to the control samples. The optimum condition was obtained at chitosan coating 0.5 %, O2concentration 8.5 %, storage temperatures 9˚C and storage time of 14 days. At this optimum point maximum of firmness, L*, taste, freshness and minimum of shrinkage, weight loss and a* were found to be 10.4 (N), 48.9, 4.35, 4.5, 6.25 %, 2.75 % and -37.28 respectively.
Mohammad Reza Amiryousefi; Mohebbat Mohebbi; Faramarz Khodaiyan
Abstract
Analysis of food surfaces is of interest because many processes depend on their complexity. Food surfaces show several textural characteristics related to their nature, composition and processing. Food surface images and their microscopic details need to be translated into numerical data before engineering ...
Read More
Analysis of food surfaces is of interest because many processes depend on their complexity. Food surfaces show several textural characteristics related to their nature, composition and processing. Food surface images and their microscopic details need to be translated into numerical data before engineering analysis. Fractal geometry is a novel concept to describe the complexity of natural shapes. In order to introduce a nondestructive method estimating the effect of process conditions on ostrich meat plates’ surface, in this research an image analysis technique was applied and the concept of fractal dimension was used to quantity the changes. Results show that fractal dimensions of the surfaces decreased with frying. Furthermore, with the increase in frying temperature, frying time and power of microwave pretreatment, a growing procedure in fractal dimension was observed. Fractal dimension as a quantity index could describe the shrinkage of deep-fried ostrich meat as a physical property.
