فصلنامه تحقیقات مهندسی کشاورزی
سال پانزدهم شماره 1 (بهار 1393)

The separation of saffron stigmas from fresh flowers is the most important and the most difficult stage of saffron harvesting. Saffron production costs are high because this harvesting stage is done by hand and is very time-consuming. One way of preserving the saffron flower is to dry it. The separating of the stigma from dried saffron flowers can then be done at an appropriate time. This study investigated the separation of the stigmas from dried flowers. The compaction and impaction forces of the loading mechanisms were evaluated. The dried flowers were loaded using pressure rollers and finger drums to test compaction and impaction forces, respectively. The effect of feed rate (2.6, 6, 8.7 g/s), roller drum speed (80, 200, 300 RPM), finger drum speed (500, 700, 900 RPM) and stage of flower development (buds, partially-opened, fully-opened) were investigated on the percentage (wt) of stigmas separated and the percentage (wt) of broken stigmas. The results showed that the percentage of separated stigma in the fully-opened and partiallyopened flowers was higher than in flower buds. The percentage of broken stigmas in the buds was 30% lower than for fully-opened flowers. The percentage of broken stigmas increased as the roller speed increased. The results suggested that the performance of finger drums was not satisfactory and that the percentage of separated stigmas was 50. A pressure roller speed of 200 rpm and a feed rate of 6 g/s were the most favorable conditions for separation of stigmas from partially-opened flowers (99.48%).

Variable rate technology is a way to reduce the environmental effects of agricultural chemicals, including fertilizer. The present study developed and evaluated the accuracy of a control system for a fluted wheel-type metering device for a fertilizer applicator. The relationship between fertilizer flow rate, traveling speed, and the opening of the metering device gate was calculated. The equation was saved in the memory of an electronic control unit. A factorial experiment was used to evaluate the effects of traveling speed (3.5, 5, 6.5 and 8 km/h-1) and fertilizing rate (70, 100, 150, 250, 350 and 450 kg/ha-1) on the accuracy of fertilizing as the percentage of deviation between the actual and target rates. The results showed that the rate of fertilizing had a significant effect of less than 1% on the accuracy of the metering device output, but no significant effect was found for traveling speed. A maximum error of 8.2% was recorded for metering device output with a mean error of 2.21%. To evaluate system performance, it was simulated in a workshop. A fertilizer prescription map for a 180 m path with 20 m interval zones having successive fertilizing rates of 50, 100, 150, 200, 250, 200, 150, 100 and 50 kg/ha-1 was loaded into the electronic control unit. A factorial experiment with a split plot design was used to evaluate the effects of traveling speed (3.5, 5, 6.5, 8 km/h-1) and fertilizing rate (100, 150, 200 kg/ha-1) on the accuracy of the fertilizing rate as the percentage of deviation between the actual and target rates. The results showed that traveling speed had a slightly significant effect on the accuracy of output (less than 5%). The rate of error of the system was less than 4.51% and was acceptable.

Saffron is an important spice values for its color, aroma and flavor in the food industry. A significant proportion of saffron compound is lost during processing and storage because of its volatility and sensitivity to oxidation. Thepresent research microencapsulated saffron color compounds (crocin) by freeze drying. The freeze-dried aqueous saffron effective compound extract was first prepared and then solutions of 5%, 10% and 15% polyvinylpyrrolidone (PVP40) and maltodextrin (MDX, dextrose equivalent: 16.5- 19.5) containing 250 mg of the freeze-dried aqueous saffron extract were prepared. The solutions were dried in a freeze dryer. The characteristics of the microcapsules (yield of microencapsulation, color remaining, bulk density, glass transition, microstructure, release speed of color compound) were evaluated at 75% humidity at room temperature (25°C) after 45 d of storage. The results showed that the crocin content of microcapsules prepared with PVP40 were higher than for those prepared with MDX. The color of the saffron compounds decreased as the wall concentrations increased from 5% to 15%. The glass transition for all samples was greater than ambient temperature. The glass transition of PVP40 was greater than that of MDX. The structure of the microcapsules was laminated and flaked. After 45 d of storage, the crocin content decreased, but the microcapsules with PVP40 had 10% higher preserved color than the other samples.

Kefiran is an exogenous microbial metabolite produced mainly by bacteria and fungi during growth. The present study investigated the effects of the addition of 3% kefiran and 3 xanthan on the extensographic characteristics of wheat dough and the shelf life of raised bread. Kefir grain was cultivated in a shaking incubator and kefiran extraction was carried using a centrifugalrefrigerator. The physicochemical properties of Sardari and Parsi wheat and their respective flours were analyzed using an Inframatic analyzer. The rheological properties of the wheat dough were measured using an extensograph and the shelf life was recorded from samples preserved in an Incobatore. Sardari wheat recorded lower values for 1000-seed weight, falling number,Zeleny index, protein, water absorption and rigidity, but higher gluten and hectoliter weights than for Parsi wheat. The addition of 3% xanthan significantly decreased (p < 0.05) wheat dough extensibility and significantly increased resistance-to-extension and energy. The addition of 3% kefiran to Sardari dough significantly increased (p < 0.05) resistance-to-extension (each period) and energy (in periods of 45 and 90 min) over the Parsi wheat and significantly decreased (p < 0.05) extensibility in both wheat doughs. The results of staling tests done at 24, 48 and 72 h showed that the addition of 3% kefiran and 3% xanthan significantly decreased crumb staling (p < 0.05). The addition of 3% xanthan decreased staling and increased hardness over the control samples. The addition of 3% kefiran and 3% xanthan extended the shelf life of Parsi wheat bread by 13 and 11 d, respectively, and the shelf life of Sardari wheat bread by 12 and 10 d, respectively.

g-oryzanol is one of the strongest antioxidants. It inhibits oxidation and is only present in rice bran. This composition decrease cholesterol, which decreases the risk of atherosclerosis. Ther prestn study extracted antioxidant from two varieties of rice bran (Zayandeh Rood and Sazandegi) using methanol solvent and percolation. The extracts were added to edible oil without antioxidants in 100 and 150 ppm concentrations and incubated at 63°C at intervals of 0, 24, 48 and 72 h. Chemical changes and thermal stability of the samples were examined using a Rancimat, and the acid and peroxide contents and radical scavenging percentage were recorded. Statistical analysis was done using a completely randomized design and Duncan's test at α = 0.01 using SPSS 16 software. All tests were replicated 3 times. The results showed that the effect of rice bran extract was greater for the Sazandegi variety for stable oxidation by oven aging of soybean edible oil for 72 h than for the addition of BHT and was significantly different from other extracts (p < 0.01).

The effect of microwave-assisted finish drying following osmotic dehydration with the application of ultrasound was investigated. Qualitative characteristics of dried black cherries (polymeric anthocyanin, loss of anthocyanin into osmotic solution, texture) were determined. Osmotic dehydration was done in osmotic solution (sucrose-water) with concentrations of 40%, 50%, and 60% sucrose. Osmotic dehydration was determined at 40, 50 and 60 °C. The influence of ultrasonic frequency at 65 and 130 KHz was also studied. To increase the permeability of skin of the black cherries, they were dipped in NaOH (0.5 mol) for 2 min. Microwave drying was done at 100 W, 200 W and 300 W to complete the drying process. Response surface methodology was used to optimize the osmotic-ultrasound-microwave drying conditions of the black cherry to achieve minimum loss of anthocyanin into the osmotic solution and polymeric anthocyanin. Experiments used a central composite rotatable design. The results showed that drying condition had a significant effect on anthocyanin loss, polymeric anthocyanin, and texture after dehydration. The optimal conditions for minimum anthocyanin loss were a temperature of 40°C, 40% concentration and ultrasonic frequency of 40.7 kHz. The optimal conditions for minimum polymeric anthocyanin were a temperature of 44.44°C, 60% concentration, 300 W of power and no ultrasonic frequency.

Administrative regulations for water flow decrease distribution efficiency and effect the economical operation of irrigation networks. Complications in distribution systems and the decrease in availability of water require study of the hydraulic performance of existing flow control structures. Control systems designed by Neyrpic (Zayandeh Rud network) and USBR (Doroodzan network) were investigated and suitable hydraulic structures were considered. The Neyrpic modules and CHO gates were used as intakes. Amil and Avio gates, static weir and sliding gate were chosen as water level regulator structures. The delivered flow rate and energy loss were analyzed for these systems and the nominal and actual flow rates to farmers were compared. Energy loss in the flow control structures (XX2, L2, C2, C.H.O, Amil, Avio, static weir and sliding gates) were measured at different flow rates and compared with allowable loss values calculated using energy lossflow rate relationships. This analysis combined with the relative error(er) and x2 allowed assessment of the most accurate and suitable system for delivering water from off-takes and water level regulators. A significant difference (p £ 0.05) was found for the flow rate in Doroodzan network, but not in the Zayandeh Rud network. Considering these results and the low error values for Zayandeh Rud network, the XX2, L2, C2 gates are recommended for discharge regulation. Amil gates and duckbill weirs are also recommended because of the minimum error and insignificant head loss in these structures.