Iranian Food Science and Technology Research Journal
Year:2008 | Volume:3 | Issue:2|Papers Count:8

Knowledge of desorption kinetics is essential to predict the behavior of the material during drying process and to design dryer equipment. The main objective of this study is to obtain the effective diffusivity coefficient and activation energy of shelled pistachio. Another goal is to find drying kinetics of shelled pistachio in fluidized bed dryer and so thin-layer characteristics of shelled pistachios were determined experimentally as a function of temperature and air velocity. Accordingly, 6 mathematical models (Two term model, Exponential model, Logarithmic model, Page model, Modified page model and Henderson & Pabis model) for describing the thin-layer drying behavior of shelled pistachios were investigated. Tests were conducted using four air temperature (25, 30, 45 and 60 C), and three air velocities (6, 8 & 10m/s). Out of the 6 models considered, the two term model was considered to be the most suitable for describing the drying behavior of the shelled pistachios. Also, for high air temperature and velocity, Henderson-Pabis model proved to be suitable. Results showed that air velocity and operating temperature enhanced the kinetics of drying of shelled pistachio and the drying air temperature had a great effect on the drying kinetics. By using of Fick’s second Law the effective diffusivity coefficient and activation energy of pistachio was determined.

Pistachio product makes a special importance in the agricultural production of Iran and is one of the main portions of non-petroleum exportation. Aflatoxin as secondary metabolites produced by the fungus Aspergillus flavus on pistachio fruits is toxic and reduces our competition in global pistachio markets. It is necessary that Iran observe international standards and make investments in marketing. We have to find new target markets for this product, particularly by eliminating fungal infection and aflatoxin production. In this study, existing position and challenges of major pistachio producing and its exporting in Iran and other countries are considered and a number of strategies are recommended.

The pistachio gardens in Iran rival other countries with 280000 hectares and rank first in the world in terms of annual production 300,000 MTs. Ecological factors for Pistachio planting favor the growth of Aspergillus flavus which produce aflatoxin as secondary metabolites which reduces Pistachio exports. It is important to control A. flavus and its aflatoxin production to increase Pistachio exportation in the country. Soil borne fungi such as Fusarium spp., Phytophthora spp. and verticilium spp. makes also root rot on pistachio trees which resulted yield reduction. It was necessary to find various ways for control management of these fungi to control wilting and inhibit toxic production on pistachio. Soil solarization and biological control application were two best methods for controlling soil borne fungi and A. flavus which are used in many countries. We used soil solarization method for controlling soil borne fungal pathogens in Kerman Application of this method reduced population density of the pathogen from 1100 CFU –g/soil to 300 after 2 weeks and reduced to 100 CFU –g/soil after 4 weeks. This method was simple, effective, no side effect and economic which can be used in nearly warm areas.

The influence of packaging system on stability during storage of raw dried pistachio nuts was studied. The pistachio nuts were packed in plastic multilayer pouches (PS/EVOH/PE) at different conditions (atmosphere, vacuum and oxygen scavenger). Accelerated Shelf Life Testing (ASLT) method was used for evaluation the storage of pistachio at 20, 35 and 50°C. Samples were analyzed at 4, 8, 12 weeks by using of split-plot design. To follow the oxidation profile, the formation of volatile oxidized products (Hexanal) was determined by GC-MS. Results showed that the formation of hexanal under all conditions was significant (p<0.05) and the oxidative process could be quantitatively controlled by decreasing the oxygen concentration surrounding raw dried pistachio nuts by the using of packaging systems. Pistachio nuts stored in oxygen scavenger system had a lower hexanal amount than both of vacuum and atmospheric systems.

A pressurized fluid extraction (PFE) method for the extraction of pistachio oil was developed using a modified supercritical fluid extractor. The supercritical fluid extraction apparatus was modified to be able to pump liquid solvent and CO2 into the extraction vessel alternatively. The experimental results showed that the extraction yield was independent of the extraction pressure. It was also noticed that addition of glass beads increased the extraction yield by more than 15%, while the extraction reproducibility expressed by RSD was improved from 4% to 1%. Furthermore, the use of glass beads reduced the solvent consumption from 35 to 20 mL. The influence of the effective variables (i.e. temperature, time, and glass beads percentage) was optimized by a factorial design method. The model allows the prediction of the extraction yield at different conditions. The PFE of pistachio oil was found comparable in terms of the extraction yield (52.6%) and fatty acid composition with the Soxhlet method. Two different solvents of n-hexane and ethanol were used for PFE of pistachio oil. The extraction yield was about one third (i.e. 18%) when ethanol was used as solvent.

Hydration characteristics of wheat kernels were studied at different soaking temperatures. Some physical properties were also evaluated as a function of soaking temperature in the range of 25 to 65 DC. Five models for describing the soaking behaviour of wheat kernels were investigated. Among them, Page model was found to be the most suitable for describing the soaking behavior of wheat kernels. Effective diffusivity of water during soaking of wheat kernels varied from 2.80x 10-12 to 1.36 x 10-11 m2/s with activation energy of 34.26 KJ/mol. In the soaking temperatures from 25 to 65 DC, studies on soaked samples showed that the kernel density decreased linearly from 2458.18 to 985.58 kg/m3 and porosity also decreased linearly from 72.33% to 27.55%, while kernel volume increased linearly from 0.022 to 0.066 cm3. A quadratic relationship between bulk density and soaking temperature of wheat kernels was developed. The amount of solids leached increased with temperature particularly for higher soaking temperatures.

Some physical properties of wild pistachio nut (Baneh) were measured by experimental method and compared with data obtained by an image processing method. The results showed a very good correlation between the results of these methods for geometrical properties of Baneh with the R2 values ranged from 0.65 to 0.90. The aspect ratio, projected area, sphericity and roundness determined by image processing were averagely 1.164, 206.68 mm2, 0.82 and 0.84, respectively. The geometric mean diameter, arithmetic mean diameter, aspect ratio, surface area and sphericity calculated theoretically based on micrometer data were averagely 7.4531 mm, 7.5285 mm, 1.134, 175.24 mm2 and 0.86, respectively. The average unit mass, 1000 grain mass, volume, true density, bulk density, density ratio and porosity were measured as 0.2045 g, 194.878 g, 0.193 cm3, 995.68 kg m-3,596.36 kg m-3,59.97% and 40.02%, respectively. The static coefficient of friction on five structural surfaces increased from 0.138 for glass, 0.180 for galvanized iron sheet and 0.266 for fiber glass to 0.436 for rubber and 0.459 for plywood. The filling and funning angles of repose were established as 16.010 and 19.92°, respectively. The terminal velocity of wild pistachio nut was 8.22 ms-1.