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.
Manoochehr Rashidi; Reza Amiri Chayjan; Ali Ghasemi
Abstract
Introduction: Tomato is one of the most valuable sources of minerals and vitamins supply in the human diet. Low shelf life of tomato and its short shelf life with inadequate processing facilities lead to heavy financial losses. Therefore, preserving and processing of tomato are of the commercial importance. ...
Read More
Introduction: Tomato is one of the most valuable sources of minerals and vitamins supply in the human diet. Low shelf life of tomato and its short shelf life with inadequate processing facilities lead to heavy financial losses. Therefore, preserving and processing of tomato are of the commercial importance. Drying is one of the preferred methods for tomato preservation. Dried tomato products including half tomatoes, tomato slices and tomato powder, have many consumptions, compared with other tomato products. Among dried tomato products, tomato powder has a particular market. Powder production is an alternative method to extend the shelf life of foods. Usually the fruit powder is very dry, humidity absorber and has too much volume. Therefore, during storage, transportation and administration, it requires special care and heavy packaging which increase the cost. To overcome these problems, compression of the fruit powder in tablet form could be a proper solution. Tablet making of fruit powder has gained much popularity due to its ease of use, storage, transportation and product formulation. After the tablet making process, the pills contain high moisture contentwhich makes them un-suitable for transportation and storage. So, in order to prevent the tablets corruption and maintain their quality, tablet drying is one of the important steps after the tablet making process. The drying process is an important operation that affects the quality and final price of the product. Different drying methods play an important role in protecting foodstuffs. However, the effect of different drying methods on the quality of some foodstuffs is not clear. Materials and methods: In this research, after the preparation of fresh tomatoes, the primary moisture content of tomatoes was determined using hot air oven method. Then, using blanching method, the tomatoes were peeled and samples were cut using a sharp razor in thicknesses of 3 mm. Tomato slices were dried using a semi-industrial dryer in a hot air at 50 °C at an air speed of 1 m/s. Dried tomato slices were powdered using a grinder. In order to homogenize the particle size, the tomato powder was sieved by a 50 mesh (Cavity size 0.5 mm) sample. Suitable moisture content to create sufficient adhesion between the particles of tomato powder was selected at %23 d.b. Water and fructose were used as a bonding agent. The process of producing tomato spherical tablets was performed by a hydraulic press. Drying tests of wet compressed tablets were performed immediately after the end of the tabletting process using a hot air drying machine with microwave pre-treatment. In this study, the effect of drying variables,through using of microwave pre-treatment along with hot air, including air temperature in five levels (40, 50, 60, 70 and 80 °C), air velocity at five levels (0.5, 1, 1.5, 2, and 2.5 m/s) and the duration of microwave application at five levels (zero (without microwave), 4, 8, 12, and 16 s) on physical properties (shrinkage and unit density), mechanical (penetration resistance) and thermal (Effective moisture diffusivity and energy consuming drying) of compact pomegranate produced from tomato powder were studied. Statistical analysis of data and optimization of drying process were performed using response surface method and central composite design. Results and discussion: Results showed that effect of air temperature and duration of microwave pretreatment on all variables of compressed tomato tablets were significant in hot air dryers with microwave pre-treatment. Increasing temperature and time of microwave pre-treatment increased the effective moisture diffusivity and shrinkage of the final product. The temperature of the air inlet to the dryer had a negative effect on the resistance to penetration, the unit density and the specific energy consumption of the drying process. Drying under lower temperature conditions and less time for microwave pre-treatment resulted in an increase in the desirability of the drying process
Hassan Sabbaghi; Aman Mohammad Ziaiifar; Mahdi Kashani-Nejad
Abstract
Introduction: Fruits and their products in the dried form are good sources of vitamins, energy and minerals. However, during the process of drying or dehydration there are changes in quality parameters in dried products. Texture is one of the most important quality attributes of fruits during drying, ...
Read More
Introduction: Fruits and their products in the dried form are good sources of vitamins, energy and minerals. However, during the process of drying or dehydration there are changes in quality parameters in dried products. Texture is one of the most important quality attributes of fruits during drying, reflecting their mechanical and microstructural properties. Apple is perishable fruit. Drying of apple is very important because of High losses are experienced during the seasonal glut. A novel process in food industry is the simultaneous infrared dry blanching and dehydration operation (SIRDBD) with intermittent heating method (radiation at constant temperature) exerted on fruits and vegetables that is known to enhance the quality of the final product. In the food industry, end-products must achieve a compromise between several properties, including sensory, sanitary and technological properties. Prediction of changes in texture during drying could be helpful in a better process control and improvement in overall acceptability of a dried snack food. The change of the elastic or viscoelastic texture of the fresh apples to rigid, fragile and brittle in the apple chips were evaluated by instrumental and sensory methods. Many attempts have been made to describe the viscoelastic behavior of dehydrated fruits and vegetables. Maxwell’s or compression models are limited to homogeneous, isotropic materials. In contrast, texture profile analysis (TPA) is more suitable for heterogeneous biological materials and shows a good correlation with organoleptic evaluation. Typical TPA parameters are including hardness, adhesiveness, springiness, cohesiveness, gumminess, chewiness and resilience. In this research, for the first time, textural analysis of dried apple slices by infrared heating at different temperatures and different moisture levels was performed. Finally, the optimum texture and overall acceptance of the product are described according to the instrumental analysis. Materials and methods: Apples (Golden Delicious variety) were purchased from a local market and kept in 0°C±1°C and relative humidity ranging from 90% to 95%. Before every thermal processing, the apple specimens were picked up from the cold storage and then they were put into use after reaching the ambient temperature. The samples were skinned manually and then cut into slices with different thicknesses of 5mm, 9mm and 13mm, all 20mm in diameter. The sliced apples were immediately subjected to simultaneous blanching and infrared drying. The texture of dehydrated apple slices using infrared radiation at three surface temperatures of 70, 75 and 80 °C were studied. The product in three thicknesses was dried to achieve a moisture level of 15, 20 and 25% wet weight basis. Then, texture profile analysis (TPA) was carried out to 50% compression strain using texture analyzer. The sensory evaluation of dried slices was also considered for desire texture (Good mouth feels texture, lack of hard tissue, no shrinkage) and overall acceptance (The final acceptability of the product in terms of total sensory properties including color, texture, flavor and aroma) by 10 professional panelists. For statistical analysis, a completely randomized design (CRD) was used in a factorial form (33) and Duncan test with 95% confidence level. Result & Discussion: The results showed that drying to studied moisture levels reduced the hardness and adhesiveness and increased springiness, cohesiveness, gumminess, chewiness and resilience in comparison with raw apple tissue. Hardness of samples dried at higher temperature was higher due to rapid removal of moisture which might have caused collapse of capillary voids inside the product. Due to shrinkage samples became denser and thus a larger fracture force was to be expected. As water content increases (i.e., higher RH) water plasticizes the cell walls and the material and product becomes softer and more pliable, thus hardness decreases. The increase of hardness could be because the rapid mass transfer that damaged the membrane and cell structure of the fruits during drying. Another important factor responsible for the increase of hardness of finish-dried samples is the low final moisture content when compared with other samples. High temperature drying method enables samples to reach low moisture content at relatively short duration and therefore the product with harder texture was obtained. The maximum value of adhesiveness was observed for fresh apples, which could be attributed to the high moisture and sugar content. Adhesiveness decreased with moisture loss, indicating the availability of free water on the sample surface. A significant decrease in springiness following high-temperature drying could be attributed to the glass transition phenomenon and changes from elastic to plastic behavior. In the period of softening, cohesiveness increased with moisture loss. Hardening caused a decrease in cohesiveness depending on the drying temperature. Gumminess is the energy required to disintegrate a semisolid food to a state of readiness for swallowing. High values of gumminess revealed “firm” and “crisp” with a cell rupture mode of tissue failure and lowest values of gumminess could be classified as “soft”. At the end of drying and with apple hardening, chewiness increased to values equal or above initial chewiness, indicating that a larger amount of energy is needed to masticate dried apples. Resilience had increasing with moisture loss. By increasing the thickness of the slices, the cohesiveness and springiness decreased and hence chewiness significantly decreased. The overall acceptance and desire texture in dried samples was observed at lower water evaporation rate conditions (lower temperatures, lower thickness and higher moisture content). In these conditions, the hardness of apple slices tissue was equal to 695.177 ± 7.685 grams. During drying of the apple, textural behavior was varied from the viscoelastic (higher initial hardness, with cohesiveness, springiness and lower resilience) to elastic and then to plastic or glassy.
Peyvand Gholipour; Mohammad Fazel
Abstract
Introduction: Ficus carica, commonly known as fig, is among the oldest types of fruit known to mankind. Drying is defined as a thermal process under controlled conditions in order to reduce the moisture in different types of food via evaporation. Edible films and coatings are used to enhance food quality ...
Read More
Introduction: Ficus carica, commonly known as fig, is among the oldest types of fruit known to mankind. Drying is defined as a thermal process under controlled conditions in order to reduce the moisture in different types of food via evaporation. Edible films and coatings are used to enhance food quality by precluding oxidation and color changes in inappropriate conditions. Carboxymethyl cellulose (CMC) is thus widely used to improve food shelf life.
Materials and methods: All experiments were carried out on fresh edible green variety figs planted in the county of Neyriz Estahban. The figs were then immersed in the following solutions:
Distilled water as a control variable without coating; carboxy methyl cellulose (CMC) solution 1% containing 0.25 gr/L glycerol; and CMC solution 1% containing 0.25 gr/L glycerol and 2% ascorbic acid. Preliminary tests including average diameter, pH, total flavonoids content, and antioxidant activity were performed on the figs. The fruits were dried using a device designed by the authors. At 60 ̊C, 70 ̊C, and 80 ̊C, the airflow in the device was 0.5 m/s, 1.0 m/s, and 1.5 m/s, respectively. After drying the samples, secondary experiments were performed which, in addition to the previous tests, included texture analysis, water reabsorption, volume measurement, shrinkage, and color analysis. A total of 27 treatments were applied in 3 rounds. A full factorial design was employed for statistical analyses while average values were compared via Duncan’s test at 5% significance. Calculations were performed using SPSS 16.0.
Results & Discussion: Using CMC coating, shrinkage increased compared to the control sample. As airflow accelerates from 0.5 m/s to 1.5 m/s, higher levels of shrinkage are observed. This could be attributed to the drier surface of the fruit caused by faster airflow. Shrinkage increases with the speed of airflow going from 0.5 m/s to 1.5 m/s. This is because at higher speeds, the sample is dried in a shorter period of time and sustains less damage.
Water reabsorption was found to decrease with higher temperature and airflow. Weak reabsorption results from the breakdown of the internal structure of the fruits.
CMC-ascorbic acid, CMC, and the control sample had the highest to lowest levels of firmness, respectively. The acid was found to preserve the internal cellular structure and preserve its breakdown. Moreover, firmness increases with the drying temperature.
According to the results, the samples coated with CMC and CMC-ascorbic acid had lower pH compared to the control sample. Airflow speed and temperature are inversely and directly related to pH, respectively.
In the CMC-ascorbic acid treatment, antioxidant capacity increased compared to the other two treatments. This may be associated with ascorbic acid’s higher ability to act as a carrier of anti-browning agents. Also, higher levels of antioxidant behavior were observed with higher temperature as it causes faster drying. Moreover, the coating acts to preserve the antioxidant and eliminates the impact of temperature.
The highest amount of flavonoids was observed in the CMC-ascorbic acid treatment followed by the control sample and the CMC treatment. This is because the ascorbic acid serves to maintain the flavonoids in the samples. The flavonoid content increases with the airflow speed since the sample is dried in a shorter duration and the flavonoids are preserved. However, higher temperature reduces the flavonoid content since heat damages the pigment.
The application of the CMC coating (alone or in combination with ascorbic acid) increased luminance compared to the control sample due to the preventative effect of the edible coating on the oxidation of the pigments in the fig samples. With faster airflows, surface moisture begins to vary which causes the coating to become lighter with higher L*. An increase in the temperature leads to lower L* as the heat causes the carotenoids and chlorophyll to break down and form brown pigments in the samples.
Using the CMC-ascorbic acid coating increases a* in figs. Furthermore, as the temperature goes up from 60 ̊C, a* also increases.
The coated samples demonstrate higher levels of b* compared to the control sample. In fact, the coating preserves the pigments and thus maintains the yellow color of the figs. The value of b* is directly related to the speed of the airflow because it decreases drying time. As a result, the product undergoes less heat. Finally, higher temperature leads to higher b* in the dried figs.
Parvin Sharayei; Hossein Chaji
Abstract
Introduction: Saffron (Crocus sativus) is the most expensive kind of spice in the world while around 400 tons of saffron are estimated to be produced in the current Iranian year (March 2016-17) from 90,000 hectares of land under saffron cultivation across the country. But, high share of producing saffron ...
Read More
Introduction: Saffron (Crocus sativus) is the most expensive kind of spice in the world while around 400 tons of saffron are estimated to be produced in the current Iranian year (March 2016-17) from 90,000 hectares of land under saffron cultivation across the country. But, high share of producing saffron is exclusively dedicated to produce and dry saffron stigma as whereas their violet color petals are mostly ignored and disposed. Saffron petal is one of the most economical sources of anthocyanin pigments. Attractive colour, functional properties and antioxidant properties of anthocyanins can make them a good substitute for synthetic pigments in the food industry. But, due to high moisture content of petals, 96.36% db, they must be dehydrated immediately to prevent the decay. In the meanwhile, the drying conditions are also too critical to petal sensitive compounds while the method of drying along with drying period and the amount of energy consumed, obviously play a significant role on price and quality of the final product.
Materials and methods: In this study, the optimization of the thin layer drying conditions of saffron petal was investigated using response surface methodology (RSM) and Face Centered Experimental Design (FCED) in order to designate the empirical expriments. Saffron petals were dried at different temperatures (40, 50 and 60◦C) and air velocities (0.7, 1.4 and 2.1 m.s-1) in a thin layer dryer and quantitative and qualitative characteristics of saffron petals (color )L: brightness; a: red – green; and b: blue-yellow, total phenolic compounds (TPC), total anthocyanin components (TAC), scavenging activity of DPPH (RSA), ferric reducing-antioxidant power (FRAP) and minimized 50% of radical-scavenging activity (IC50) contents) were invetigated.
Results & discussions: Maintaining the quality of final dried product as high as possible is a major concern while it is an important aspect to consider for use of phenolic compounds and anthocyanins as antioxidants and colorants in food industry. The results showed that the total phenolic compounds (TPC) and total anthocyanin content (TAC) had a remarkable increase with temperature rise from 40 to 50◦C while more temperature increase brought about sharp drops. But, an increasing trend of variations is observed in parallel with increases in velocity of drying air for each temperature. The rise in anthocyanin and phenolic content is more attributed to much significant reduction in drying duration from 40 to 50◦C in comparison with 50 to 60◦C. It was also observed that total antioxidant activity of dried saffron petals showed the same response as TPC and TAC to temperature rise from 40 to 50◦C. Such behaviour could be explained by the findings of other researchers in which the antioxidant activity has high correlation with anthocyanin content and total phenolic composition of food materials. As a complementary, it can be mentioned that polyphenols in an intermediate stage of oxidation have greater antioxidant power than initially even though this is temporary; furthermore high temperature stabilization procedures may lead to the formation of new compounds with higher antioxidant activity. This is essentially the case of the Maillard reaction, which creates various Maillard reaction products, with markedly higher antioxidant power.
Conclusion: Generally, according to Derringer’s desired function approach, the optimal conditions were 50◦C and 1.4 m.s-1.The experimental values agreed with those predicted values. At this optimum condition, the TPC, TAC, DPPH, FRAP, and a value of the dried saffron petal were found to be 46.39 mg/ g ,1205.58 mg/l, 52.97%, 1276.52 µmol Fe2+/l, and 11.13, respectively. The experimental values were in a good agreement with the predicted values.
Shohreh Nikkhah; Nasser Sedaghat
Abstract
This research was carried out in order to investigate on the effects of packaging type and storage temperature on qualitative and quantitative characteristics of dried melon. “Thashkandi” and ‘ Khatoni” melon varieties؛ osmotic solutions of 0% and 10% sucrose and cabinet dryer ...
Read More
This research was carried out in order to investigate on the effects of packaging type and storage temperature on qualitative and quantitative characteristics of dried melon. “Thashkandi” and ‘ Khatoni” melon varieties؛ osmotic solutions of 0% and 10% sucrose and cabinet dryer were applied for dried melon production. Dried fruits were packed with modified atmosphere (PE-PA film, 85 micron thickness, two gas mixtures: (70% CO2%, 30% N2(1) and 60% CO2%, 40% N2(2)) and without modified atmosphere (polyethylene and polystyrene films). After 6 months results showed that control dried in 10% osmotic solution preserved in 25°c and 4°c treatment had the most and the least firmness respectively. Melon pretreated by 10% osmotic solution, packed in atmosphere 1 had the least water activity. Dried melon preserved in 4°c had higher L*(brightness) and b*(yellowness) indices. Khatooni cultivar produced dried melon with higher a*(redness). Dried melon pretreated by 10% osmotic solution and packed in atmosphere 2 had less a*(redness). Furthermore dried melon pretreated by 10% osmotic solution and packed in atmosphere 2 and preserved in 4°c had minimum O2% and maximum CO2% in package.
Mohamad Mehdi Heydari; Seyed Mehdi Nassiri
Abstract
Introduction: Given that fruit drying is one of the best economical storing methods, in the present study attempt has been made to apply a commercial drying method, namely passing warm air through fruit in a cabinet drier, to pinpoint the change in textural properties of pear fruit during drying at different ...
Read More
Introduction: Given that fruit drying is one of the best economical storing methods, in the present study attempt has been made to apply a commercial drying method, namely passing warm air through fruit in a cabinet drier, to pinpoint the change in textural properties of pear fruit during drying at different inlet air temperature and velocity levels. The outcomes of the study can be used for optimizing the drier operation during drying (intelligent driers) to keep suitable textural properties of final product for those who use sweet dried fruit as sweetener due to diabetic issues.Materials and method: Pear fruits, Shah Miveh cultivar, were collected form a garden near Isfahan city and carried to the laboratory carefully. Experimental samples with 2×2.5×2.5 cubic centimeter dimension were prepared from upper part of pear fruits. A conventional cabinet drier was used for drying the pear cubes with adjustable inlet drying air temperature and velocity. Air temperature and velocity were adjusted at three levels of 40, 50 and 60 oC, and 0.5, 1 and 1.5 m/s, respectively. Initial moisture content was measured by gravimetric methods and samples weight loss measured during drying by an online system comprising hooked type balance with ±0.001 accuracy. Dried samples were then subjected to texture profile analysis (TPA) with Instron (Santam-STM 20). Two-bite test was performed with 20 mm diameter aluminum probe, at 1 mm/s speed rate for 5 mm deformation. Textural properties of samples such as hardness, cohesiveness, adhesiveness, springiness and chewiness were drawn from force-time curve. Textural properties were measured at five sample moisture contents of 82, 66, 51, 35 and 20 percent (w.b.). Data were analyzed according to the factorial experiments based on completely randomized design by SPSS software (version 16), and the means were compared by Duncan multiple range test at 5 percent of significance. Results and Discussion: Mean comparison of drying time significantly affected by air temperature and velocity, and the effect of temperature was more than air velocity. Results revealed that textural properties of samples have changed during drying process and these changes were related to drying conditions. Hardness decreased exponentially and adhesiveness decreased linearly as fruits were being dried, whereas springiness and cohesiveness increased linearly. Chewiness followed a parabolic trend, reached to the peak in the range of 40 to 50 % moisture content levels (wet basis). ANOVA showed that drying air temperature had significant influence on hardness, springiness and chewiness, while its influence on adhesiveness and cohesiveness was not significant. Moreover, it was found that air drying velocity affected all aforementioned properties. Having considered the results of dried pear chewiness, the minimum chewiness (0.46 J) took place at air drying temperature of 40 ˚С and velocity of 1m/s, and therefore it is recommended as the best drying condition. Drying time period at this condition was measured nearly 33.5 hours, which was approximately 24 hours more than the shortest one in the drying condition of 60˚С and 1.5 m/s and 6.5 hours lower than the longest one in drying condition of 40˚С and 0.5 m/s.
Azam Ayoubi; Nasser Sedaghat; Mahdi Kashani-Nejad; Mohebbat Mohebbi; Mehdi Nasiri mahalati
Abstract
The purpose of this research was study effect of drying conditions (temperature at three levels of 60,70, and 80 oC, air velocity at two levels of 1/5 and 2/5 m/s, and four pretreatments including potassium carbonate and paksan oil, olive oil, hot water and no pretreatment (control)) on drying grape ...
Read More
The purpose of this research was study effect of drying conditions (temperature at three levels of 60,70, and 80 oC, air velocity at two levels of 1/5 and 2/5 m/s, and four pretreatments including potassium carbonate and paksan oil, olive oil, hot water and no pretreatment (control)) on drying grape process and quality of raisin including rehydration, shrinkage, hardness and browning index. The results showed that temperature, air velocity and pretreatment have significant effects on drying rate and quality of raisin. Drying rate increased with increasing temperature and air velocity and with application of preatreatment. The best values of hardness (0.73 N), shrinkage (81/04%) and the least value of browning index (0/157) were related to dried raisin at 60 oC and most value of rehydration (1/266) was related to dried raisin at 70 oC. Air velocity just significantly affected on browning index. Increasing air velocity decreased browning index. Also between used preatreatments , potassium carbonate and paksan oil caused best physicochemical results.
Amir Salari; Mostafa Mazaheri Tehrani; Seyed Mohammad Ali Razavi
Abstract
In this study, mathematical modeling of hot air baking-drying of thin-layer crisp bread was investigated. Thin-layer drying process were conducted under three different temperatures of 110, 150 and 190 °C at a constant air velocity of 0.5±0.1 m/s and absolute humidity of 0.6 ± 0.04g ...
Read More
In this study, mathematical modeling of hot air baking-drying of thin-layer crisp bread was investigated. Thin-layer drying process were conducted under three different temperatures of 110, 150 and 190 °C at a constant air velocity of 0.5±0.1 m/s and absolute humidity of 0.6 ± 0.04g water/kg dry air. It was found that the baking-drying process occurred in falling rate period over the baking-drying times. Eight well-known thin-layer baking-drying models were fitted to the baking-drying experimental data of crisp bread, implementing non-linear regression analysis techniques. Based on the coefficient of determination (R²) and root mean square error (RMSE) values, it was concluded that the best models in terms of fitting performance for hot air baking-drying of bran free crisp bread were Wang & Singh and Logarithmic while for whole-wheat crisp bread were Page, Logarithmic and Wang & Singh. The moisture transfer from crisp bread was described using the Fick’s diffusion model. The effective diffusivity was within the range of 2.88×10-8 to 1.11×10-7 m2/s for bran free crisp bread and from 2.47×10-8 to 8.84×10-8 m2/s for whole-wheat crisp bread over the temperature range. The activation energy for bran free and whole-wheat crisp bread was found to be 25.22 and 23.43 kJ/mol, respectively..
Ghasem Yousefi; Zahra Emam-Djomeh
Abstract
The present research surveyed the effect of five factors including: microwaves power, air temperatures and its flow rates, microwaving time onset and amount of substances on the requested time and energy for combined fluidized bed- microwaves drying of black raspberry into 50% dry base wet content. Response ...
Read More
The present research surveyed the effect of five factors including: microwaves power, air temperatures and its flow rates, microwaving time onset and amount of substances on the requested time and energy for combined fluidized bed- microwaves drying of black raspberry into 50% dry base wet content. Response surface methodology and Central composite was used as experimental design. Multiple linear regression was used for obtaining second polynomials models for each analyses followed by ANOVA analysis in order to confirming the adequacy and accuracy of resulted models. Using the empirical resulted model the relationship between variables and responses were determined via response surface method. Correlation coefficients of the regression models were 0.964 and 0.970 respectively for the drying time and energy consumption. The Optimized drying condition were including; 600 watts for microwaves power and microwaving onset from that time as the moisture content was 344% decreased,73 g for amount of substances, and 85˚C and 15 m.s-1 for air temperatures and its flow rates respectively. Under mentioned conditions, the fitted model was predicted 52.66 Min and 65.2 Kj respectively for the requested drying time and energy consumption at combined drier. As a conclusion, the results showed that requested drying time and energy consumption were decreased with increasing of temperatures, microwaving time and its power, and decreasing of air flow rates. In this regard, the drying kinetics curve samples were drawn under the conditions listed that showed drying time is reduced to 76% with increasing temperature from 55 to 85 and use the microwave reduced drying time until 30 to 80%.
Farideh Tabatabaei Yazdi; Mohebbat Mohebbi; Seyed Ali Mortazavi; Arash Ghaitaranpour; Behrooz Alizadeh Behbahani
Abstract
The effects of a couple of factors (cooking period of wheat: 0, 1 and 3.5 h and temperature of drying 70, 80 and 90 ْC) on drying behavior of Tarkhineh during hot-air drying has been investigated. Tarkhineh pill samples with 8 cm diameter and 11 mm thickness were dried to 0.64(d.b). Results showed that ...
Read More
The effects of a couple of factors (cooking period of wheat: 0, 1 and 3.5 h and temperature of drying 70, 80 and 90 ْC) on drying behavior of Tarkhineh during hot-air drying has been investigated. Tarkhineh pill samples with 8 cm diameter and 11 mm thickness were dried to 0.64(d.b). Results showed that cooking of wheat led to higher water absorption of Tarkhineh dough, while increased drying rate. On the other hand, increasing drying temperature resulted in higher drying rate of samples. The effects of temperature on drying rate was pronounced in raw samples compared to cooked ones, which could be attributed to the cracking in the cooked samples during drying . Drying kinetics of Tarkhineh in raw samples unlike cooked samples presented a falling rate period followed by a constant rate period. The effective moisture diffusion coefficient of Tarkhineh varied between 1.611E-10 & 7.822E-10 (m2/s)) for the given temperature range) and corresponding activation energy was between 37.928 and 17.941(kJ/mol) respectively.
Hassan Afshari Jooybari; Asgar Farahnaki; Mahsa Majzoobi; Gholam Reza Mesbahi; Mehrdad Niakosari
Abstract
Mazafati date is a wet and semi-dried date fruit type with dark red to black color that has premier quality. Because of its high moisture content, date fruits of this variety are very perishable at room temperature and therefore must be refrigerated during storage. In this study, effect of air temperature ...
Read More
Mazafati date is a wet and semi-dried date fruit type with dark red to black color that has premier quality. Because of its high moisture content, date fruits of this variety are very perishable at room temperature and therefore must be refrigerated during storage. In this study, effect of air temperature (50, 60, 70, 80 and 90 ˚C) and air flow rate (1, 1.5 and 2 m/s) in hot air drying of Mazafati date were investigated. The results showed that for all samples, drying occurred at the falling rate stage of drying and the main factor affecting the drying rate was air temperature. Air flow rate did not have significant effect on drying rate. Overall, it was concluded that moisture of Mazafati dates can be reduced by cabinet drying and therefore using drying process, the need for their cold storage can be eliminated.
Shahla Khodabakhsh Aghdam; Mahdi Moradi; Alireza Yousefi
Abstract
In this research, Papaya slices with dimensions of 0.5×2×5 cm3 were dried at 45 °C using a cabinet dryer in which drying air velocity and relative humidity were 0.9 m/s and 30%, respectively. The moisture diffusion coefficient of Papaya was determined in this drying condition. Mass transfer equation ...
Read More
In this research, Papaya slices with dimensions of 0.5×2×5 cm3 were dried at 45 °C using a cabinet dryer in which drying air velocity and relative humidity were 0.9 m/s and 30%, respectively. The moisture diffusion coefficient of Papaya was determined in this drying condition. Mass transfer equation with its boundary conditions was solved based on finite difference method. Finally, coefficient of determination and goodness of fitting between the gained theoretical model by solving mass transfer equation, and experimental data were obtained R2=0.996 and RMSE=0.00115. Therefore, finite difference numerical method showed a suitable correlation with low error into the experimental data for solving of mass transfer equation.
Adeleh Soleimani; Mohammad Javad Varidi; Alireza Sadeghi Mahoonak; Mehdi Nasiri mahalati
Abstract
This study was carried out to evaluate the chemical compoition of Alosa Caspia and results compared with Clupeonella engrauliformis which is a common fish catch among Clupeonella and Clupeidae spp in Caspian sea . Results showed that the amount of fat, protein, ash and dry matter in Alosa was higher ...
Read More
This study was carried out to evaluate the chemical compoition of Alosa Caspia and results compared with Clupeonella engrauliformis which is a common fish catch among Clupeonella and Clupeidae spp in Caspian sea . Results showed that the amount of fat, protein, ash and dry matter in Alosa was higher than Clupeonella. The fatty acid composition showed that the EPA was very high in Alosa that show this fish is rich source of omega-3 fatty acid. Then the effect of salting method on moisture and salt content Alosa Caspia were evaluated. The salting methods including traditional (common in north reigon), brining with two salt concentration (saturated and 20% w/w brine) followed by two drying methods (sun and oven drying at 30°) were used. The texture changes during salting showed that salt absorption and water loss was different in different salting method and was higher in traditional salting method. These samples had the lowest moisture at the end of salting, but showed the highest moisture at the end of drying.
