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Showing 14 results for Drying

O. Asadi Aghdam, S. J. Tabatabaei , J. Hajilou,
Volume 3, Issue 8 (6-2013)
Abstract

This experiment was conducted to study the effects of application of partial root zone drying technique on quantitative and qualitative characteristics of strawberry (Fragaria ananassa cv. Selva). The experiment was arranged as randomized complete blocks design with five treatments and four replications. One week after planting the seedlings, different irrigation regimes including FC: FC (moisture content in both sides of the roots at field capacity), FC: 1/2 FC (moisture content in one side of the roots at field capacity and in the other side at half field capacity), FC: Dry (moisture content in one side at field capacity and the other side is dry), ½ FC: Dry (moisture content in one side at half field capacity and the other side is dry) and 1/2 FC: 1/2 FC (moisture content in both sides of the roots at half field capacity) were applied by emitters (and controlled by moisture sensors). Traits such as fresh weight of vegetative parts and fruits, leaf number of leaves, chlorophyll index, leaf area index, leaf leakage of electrolytes, proline, and soluble solids were measured. Results showed that the highest fresh weight of vegetative parts and fruits, number of leaves, chlorophyll index and leaf area index were measured in FC: FC and FC: 1/2 FC treatments. Maximum electrolyte leakage, proline and soluble solids were in 1/2 FC: Dry treatment. Plants under this technique showed resistance mechanisms, against drought stress, such as proline production and reduction of number and surface of leaves.
P. Ghorbani, H. Sarikhani, M. Gholami, E. Ahmadi,
Volume 4, Issue 12 (8-2014)
Abstract

Alkaline treated raisin is one of the most important raisins produced from Bidaneh Sefid grape in large scale in Iran. In current research, effects of potassium carbonate on drying rate, antioxidant activity, total phenolics and color of raisin were investigated. Raisin was produced sun-dried (as control), cold and warm alkaline at four concentrations of 0.75, 1.5, 3 and 6 percent of potassium carbonate. Results indicated that by increasing concentration of potassium carbonate and using warm solution, drying time reduced. Furthermore, raisin pre-treatment highly affects on total phenolic content and antioxidant activity. The highest content of totol phenolic and antioxidant activity were observed in warm 6% potassium carbonate treated raisins. In addition, warm-alkaline treated raisin showed higher total phenolic and antioxidant activity in comparison to those of cold-alkaline treated raisins. Production method revealed a significant effect on color, drying rate and antioxidant properties of Bidaneh Sefid. It seems the higher speed of drying helped in marinating polyphenol content and higher antioxidant activity. Based on current result, pre-treatment of grape by warm potassium carbonate solutions at lower concentration is suggested for marinating phenolic compounds.
E. Mehryar, M. Sadeghi, S. J. Razavi, E. Forghani,
Volume 5, Issue 16 (9-2015)
Abstract

Drying of fruits and vegetables is one of the oldest methods for preserving foods. Drying not only affects the moisture content of the product, but also changes other physical, chemical and biological properties of the product including enzymatic activity, microbial spoilage, viscosity, hardness, taste and aroma. In order to study the occurring changes in dried product, qualitative characteristics including shrinkage, color and water rehydration are commonly evaluated. The purpose of this research was to study the effect of drying methods on qualitative indices for dried Istamaran dates. The drying methods were hot air, microwave and vacuum drying. The photos of the final product were taken using a digital camera. Then, color parameters (L*, a* and b*) of the samples were measured using Photoshop software. The amount of shrinkage for dried product was determined by liquid displacement method. For evaluating rehydration ability, water absorption capacity (WAC), dry matter holding capacity (DHC), and rehydration ability (RA) were also estimated. Results showed that the effect of drying method on WAC, DHC, and RA was significant (p<0.01). Means comparison revealed that the structural damage into the final dried product occurred by microwave method was higher than that for hot air and vacuum drying methods. Drying method did not lead to any significant difference among shrinkage values. Drying temperature influenced shrinkage more than drying time. Analysis of variance showed that the effect of drying method on L*, a* and b* parameters was not significant. Since the temperature of drying in microwave method is very high, it is possible that caramelization occurs during this method. This phenomenon can be considered as the reason of color darkness caused by microwave method.
A. Ghasemi, M. Sadeghi, S. A. Mireei,
Volume 5, Issue 18 (2-2016)
Abstract

One of the factors which affect the quality of rice during milling is internal fissures created during and after drying operation. In many industrial countries intermittent drying method is hired to reduce the moisture content of rough rice in order to reduce the drying time and maintain the quality of the final product. A high percentage of rice breakage during milling process, at least in Iran, necessitates performing the intermittent drying process and optimize it for Iranian varieties. In this study, the effect of this method (drying-tempering) and continuous drying method (no tempering) on fissuring percentage of Hashemi (long grain) and Koohsar (medium grain) varieties was investigated. The experiments were carried out at constant drying and tempering temperature of 60 °C, drying durations of 20, 40 and 60 min, and tempering durations of 0 (continuous drying), 40, 80, 120, 160, 200, 240 min. The results revealed that the tempering process significantly reduced the drying time and fissured kernels percentage. Moreover, for both varieties it was observed that the rice fissuring decreased significantly by continuing the tempering process until certain durations. Overall, for optimization of intermittent drying process in terms of the considered qualitative parameters, i.e. reducing energy consumption and losses, conducting 160 and 200 min tempering process after 40 min drying was found appropriate for Hashemi and Koohsar varieties, respectively. In addition, according to the higher fissuring for Koohsar (medium grain) compared to Hashemi (long grain), it can be concluded that physical properties such as kernel slenderness ratio is effective on its fissuring.


R. Amiri Chaijan, M. H. Khosh-Taghaza,
Volume 7, Issue 4 (1-2004)
Abstract

Traditional paddy dryer systems in Iran cause considerable losses in rice production due to non-uniform drying. In order to decrease the amount of kernel fissuring and to increase the drying rate, fluidized bed method was applied in this study for rough rice drying at temperatures higher than normal. An experimental dryer was used for drying the samples. The drying experiments were set up to find kernel fissuring percentage and the drying times under three conditions: fixed, minimum, and full fluidized bed conditions at temperatures of 40, 60 and 80oC. Results showed that the amount of kernel fissuring, at minimum fluidization compared to fixed bed condition, decreased 57%, 68% and 75% at temperatures of 40, 60 and 80oC, respectively. This reduction at full fluidization compared to fixed bed condition, at the above temperatures, was 40%, 54% and 65%. The minimum fluidization method took the lowest and the fixed bed method took the highest drying time. It was concluded that the minimum fluidization drying method had the lowest fissuring and drying times at all experimental temperatures.
M. Soleymani, M. Shahedi,
Volume 10, Issue 1 (4-2006)
Abstract

The Drying process is one of the most important factors which are effective on the milling quality of rice and its economic value. In order to investigate the effect of dryer parameters on milling quality of rice and their relationships, one of the usual rice varieties (Binam) of Gilan province with an average milling quality and the initial moisture content of 20.5% was selected. Drying process was performed on the basis of a complete randomized design with 20 treatments and 3 factors including temprature (at five levels of 30, 40, 50, 60 and 70 °C) , air velocity (at two levels of 0.5 and 2 m/s) and final moisture content of paddy (at two levels of 10.5% and 14% on wet basis equal to 11.7% and 16.3% on dry basis respectively). Results of the experiments indicated that increase of temprature or air velocity reduces drying time but increases drying rate constant (K). It also revealed that decrease of final moisture content of paddy increases drying time significantly, but doesn’t have any significant effect on drying rate constant (K). Correlation test indicated that milling loss (breakage) has a negative relation to drying time and a positive relation to drying rate constant(K), however, bending strength has a positive relation to drying time and a negative relation to constant of K. Regression of qualitative properties of paddy including: milling loss (breakage) and the bending strength over drying time and constant of K revealed that drying time is a better criterion for predicting the mentioned qualitative properties.
M. Kh. Pirouzi Fard,
Volume 10, Issue 2 (7-2006)
Abstract

In the present study, the effects of sodium metabisulphite concentration (2, 4, 6, 8, 10%), dipping time (2.5, 5.0, 7.5, 10 min.) mixing of the solution including: continuous mixing , once per 2.5 minutes , once per 5.0 minutes and without mixing (I, II, III, IV) and pH of the solution (4.62, 3.62, 3.42) on the absorption of sulphure dioxide by halved Riogrande variety tomatoes prepared for sun drying were investigated. The experiment design was completely randomized plots with the order of 5, 4, 4 and 3 treatments, each with four replications. The results showed that increasing the solution concentrations, dipping time, mixing and decreasing pH increased the rate of SO2 absorptions. The increment of SO2 in tomato under the effect of the above mentioned factors have been shown in different tables and figures. The mathematical models of relationship among the rate of absorption of SO2 , the concentration of sodium metabisulfite solution, dipping time, also the effect of metabisulfite solution pH were developed. Significant differences were found in these increments in all the treatments (α= 0.01).
Sh. Rafiee,
Volume 10, Issue 3 (10-2006)
Abstract

Rapid drying can increase brittleness of and induce internal cracks in the grain which predispose the product to breakage during subsequent activities. To fully understand the drying process requires an accurate description of the drying mechanism. Kernel equilibruim moisture content (EMC) is a property strongly related to agricultural products drying phenomena. Its accurate prediction can lead to optimisation of drying processes, especially in highly automated computer aided drying systems. In this study, a finite element formulation and solution of a set of coupled conductive heat and diffusive moisture transfer equations, to improve grain drying simulation of axisymmetric bodies are presented. Axisymmetric linear triangular elements with two degrees of freedom per node are used to discretize the rice grain in model for different equilibrium moisture content (from 7.5 to 0.12 d.b.%). For the purpose of this study, one medium grain, ‘Sepidrod CV.’, was used. During the thin layer drying, the drying air temperature of 69 °C and initial moisture content of 17.23 d.b.%, were adopted. A high relation has been observed when the output of model with 11.5 d.b.% EMC was compared to experimental data obtained by others. The least and most root mean square error analysis (RMSE) calculated for models at different EMC with experimental data were 0.0091 and 0.1025. The least and most mean relative deviation modulus were 1.394 and 5.129, respectively. Considering the mean errors of the models in relation to the obtained experimental data, the equilibrium moisture content for 11.5 d.b gave the best result.
A. Sadeghi, F. Shahidi, S.a. Mortazavi, M. N. Mahalati, S.h.r. Beheshti,
Volume 12, Issue 43 (4-2008)
Abstract

The aim of this study was to use Alpha-amylase termamyl 2-x for maltodextrin production from corn starch and evaluate its industrial uses. Based on the results obtained in laboratory, this process was accomplished in pilot plant scale. The process included preparation of starch suspension, pH adjustment, addition of enzyme, heating under stirring, continuous control of DE and Brix, enzyme inactivation in adequate DE, separation of soluble sections by centrifuge and finally spray-drying of the maltodextrin liquid. In this investigation, the amount of DE at dry matter was calculated under three enzyme concentrations (0.2, 0.25 and 0.3 ml of Alpha-amylase termamyl 2-x per Kg of starch) and in three different hydrolysis temperatures (60, 65 and 70 ºC) at constant pH (6). A completely randomized design with factorial arrangement and 5 replications was conducted. To study the relationship between DE and different parameters, multiple linear regression was used. Finally, for approximation of DE (based on enzyme concentrations, temperatures and hydrolysis times) a regression model was used. The results from different enzyme dosages at the same temperature and time of hydrolysis differed significantly (p≤ 0.05). Meanwhile, the best enzyme concentration and hydrolysis temperature for maltodextrin (high DE) production after 300 minutes were 0.25 ml of enzyme per kg of starch and 70 ºC, respectively. In these conditions, the least residual starch concentration and residual Alpha-amylase activity were observed.
A Farahanaki, Gh Mesbahi, H Askari,
Volume 12, Issue 46 (1-2009)
Abstract

Date fruit as a high calorie and valuable food source can be one of the main Iranian agricultural commodities for export, if properly processed and packed. The aim of this study was to process Kabkaab date variety from Routab (high moisture dates) to Tamar (known as dates or dry dates) using an industrial cabinet dryer. The Routab samples were dried using hot air at 56, 66, 76, 86 and 96 ˚C and changes in weight, moisture, pH, colour, texture and density of the dried samples were monitored. The results indicated that at 56 and 66 ˚C, drying rate was too low to be economic for an industrial process. At 86 and 96 ˚C the drying rate was high, although quality factors like colour was not acceptable. Therefore 76 ˚C is recommended as the best temperature for drying dates fruit. Moisture range of 24-27% (db) was the critical moisture level where a sharp decrease was observed in drying rate. Textural experiments of dates fruits with a wide range of moisture contents showed that above 30% moisture the hardness does not change with moisture level however, below 30% a small change in moisture can have a considerable impact on texture.
F Goodarzi,
Volume 12, Issue 46 (1-2009)
Abstract

To optimize the use of sulfur in drying of apricot, four following treatments including: sulfiting and drying, sulfiting- blanching and drying, blanching- sulfiting and drying, and finally sulfiting- drying to % 50 of initial moisture- blanching and finish drying were studied. The levels of sulfur addition were from 0 to 1500 ppm, SO2 and drying was carried out at 50 to 74 °C. The quality of dried apricots was judged by extent of browning development and hardness determination. A response surface statistical design was applied to evaluate the quality of slabs and to determine optimum drying conditions. The results showed that sulfite was the major factor in controlling dried apricot quality. At present of sulfur, the role of temperature can be neglected. The amount of used sulfite has no significant effect on drying time of apricots. Blanching reduced drying time of product significantly. By increasing the drying temperature, loss percentage of SO2 was reduced for all treatments. Blanching and then sulfiting, increased loss in residual sulfur of products significantly. Application of sulfiting– drying method, using 900 ppm of SO2 at 50 to 68 °C was found to be the best treatment because of production of slabs whit average hardness and color texture equal to 1.44 N/m2 and 0.07 Od respectively.
A Akbari, M Shahedi, N Hmadami, Sh Dokhani, M Sadeghi,
Volume 13, Issue 47 (4-2009)
Abstract

Sun drying is a well-known food preservation technique that reduces the moisture contents of agricultural products. Shrinkage, rehydration ability and color of food materials during air drying adversely affect the quality of the dried products. Since all fresh tomatoes can not be consumed at the time of harvest, preservation provides a larger market, allowing consumers to buy the preserved tomato through the year. A natural convection solar dryer consisting of a solar air heater and a drying chamber was manufactured in this research. Tomato slices were dried in the solar dryer and compared with open sun drying. Also, tomato slices were dried in a laboratory oven (operated at temperature 50, 60, 70, 80°C). With increasing the temperature, the time required to arrive certain moisture content is decreased. Also results showed that drying time in the solar dryer is shorter than open sun drying. In other words, drying time was reduced 17 to 45% by the solar drying in comparison to open – sun drying. The experimental shrinkage data showed a linear behavior with moisture content. Also, the experimental data didn't show a strong effect of temperature on the rehydration ability of the product. Thus, the effect of temperature and method of sun drying on the shrinkage phenomenon and the rehydration ability can be neglected. Tomato slices dried at 50°C had better appearance (lightness and red color) than at 80°C.
M Hoseeini Ghafari, Gh Ghorbani, H Rahmani,
Volume 13, Issue 47 (4-2009)
Abstract

This study was conducted to determine the influence of two intermittent (1wk) and abrupt drying off methods on udder health index of dairy cows with 30d dry period. Eighteen multiparous dairy cows were dried off approximately 4 wk prior to the expected calving time in a completely randomized design. For intermittent milk cessation treatment, cows were dried off in the following manner. Milk samples were collected from front and rear quarters at 7d to 3d prior to drying off, at drying off, 14d, 7d prior to calving, at calving, and 7d post calving. Milk yield at drying off day was recorded. Lacteal secretion samples were stored at -18Ċ and used for lactoferrin quantitation. Other samples were stored at 4Ċ for somatic cell count, total bacteria count and other milk components. The results indicated that, there were no differences in fat, protein and lactose percentages and milk pH between two drying off methods (P>0.05). However, there was a significant effect of drying off methods on lactoferrin concentration it was higher in dairy cows dried off by intermittent milk cessation, applied in 2 and 1 wk prior to calving time (P<0.01). Total bacteria count was not different in the two drying off methods. Milk total bacteria counts was higher in rear quarters compared to front quarters (P<0.05). Milk somatic cell counts were higher in cows dried off by abrupt milk cessation (P<0.05). There was a positive correlation between milk somatic cell counts and total bacterial counts (r = 0.352, P<0.01). No significant difference was observed in colostrum and milk lactoferrin concentration, somatic cell counts, fat, protein and lactose percentages, between rear and front quarters. With respect to higher lactoferrin concentration in cows dried off by intermittent milk cessation and due to antibacterial action of lactoferrin against mastitis pathogens, it seem that intermittent milk cessation treatment is preferred for cows given short dry period.
M Moradi, A Zomorodian,
Volume 13, Issue 48 (7-2009)
Abstract

In this work, a cabinet solar dryer for thin layer drying of Cuminum cyminum was evaluated in two conditions (Indirect and Mixed). Four levels of drying air flow rates (three active and one passive) were adopted. The experiments were performed in a completely randomized Block design pattern in three replications. Drying durations were kept constant (90 min) for all the experiments. Average initial moisture content of Cuminum cyminum was 43.5 %( db) and the product was set to be dried for 90min in the solar dryer (average 8%d.b). The effects of the drying air flow rates and modes of drying were highly significant in final moisture content of Cuminum cyminum. Duncan test was selected to evaluate the effects of different factors on average moisture content of the samples. The results showed that the passive air flow system in mixed mode drying conditions for drying the Cuminum cyminum was best. The drying duration for the mentioned condition was 55min to dry the product from 43.5% to 8 %( db). The experiments were conducted each sunny day of August-September 2007 from 11.30 till 13.The average solar irradiance was recorded 750 W/m2 average ambient air temperature was32°C and average ambient relative humidity was20%. Using the dryer in the best selected conditions reduced the moisture content of the product from 43.5% to 4.95% after 90 min.

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