Reza Farahmandfar; Somayeh Salmani; Hoda Fahim
Abstract
Introductıon: Nuts are one of the major resources of bioactive compounds such as tocopherols, tocotrienols, sterols (Jensen and Lauridsen, 2007). Tocopherols include 8 natural homologues that all of them belongs to vitamin E group (Chun, 2002). It is well known that vitamin E has good antioxidant activity ...
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Introductıon: Nuts are one of the major resources of bioactive compounds such as tocopherols, tocotrienols, sterols (Jensen and Lauridsen, 2007). Tocopherols include 8 natural homologues that all of them belongs to vitamin E group (Chun, 2002). It is well known that vitamin E has good antioxidant activity and among its isomers, α-tocopherol and γ-tocopherol have highest biological activity and free radical scavenging, respectively (Grilo et al., 2014). In recent years, the beneficial health effects of vitamin E on some disease such as cancer and heart disorders attract researcher’s attentions (Wagner et al., 2004).Roasting process changes the chemical and nutritional properties of nuts, including antioxidants, vitamins, colors, and aroma mostly through Maillard reaction (Alamprese et al., 2009; Ballistreri et al., 2009). Due to the importance of vitamin E antioxidant activity and its heat sensitivity, the residual amounts of them after different roasting conditions were investigated. Materials and methods: Samples were spreaded in alominum foil and placed in forced air oven at 120 and 150 ºC and different time intervals including 0, 20, 30 and 40 min. After roasting, samples were powdered, then 0.5 g of each sample plus 0.05 g ascorbic acid were added to 0.5 mL ethanol (90.2%) and 0.5 mL KOH and mixed in a tube (16× 125 mm). The tube was then placed in water bath for 30 min. Then, the tube were placed in ice bath for 5 min, then 3 mL deionized water, 5 mL hexane were added to the tube and vortexed for 30 s and centrifuged for 10 min at 1000 rad/s at ambient temperature. The extraction was done twice. Hexane layer evaporated with nitrogen then 1 mL of mobile phase added to tube and vortexed again. Prepared samples then were injected to HPLC (Knuer- Germany). Results and discusion: Based on the obtained results, α-tocopherol content in almond was more than γ-tocopherol. After 20 and 30 min of roasting, at 150 and 120 ºC respectively, the amount of α-tocopherol slightly increased, while it decreased with increasing roasting time. γ-tocopherol content in almond at both temperatures also increased up to 20 min roasting and decreased till the end of process. In hazelnut, at both temperatures up to 20 min and then decreased till end of roasting process. This trend was shown for peanut tocopherols as well. With increasing in roasting time, α-tocopherol and γ-tocopherol content decreased to their initial level. It has suggested that tocopherols which attached to the other components such as phospholipids released more conveniently under thermal treatment like roasting which leads to increase their concentrations at initial of thermal process. In pistachio, 150 and 120 ºC respectively caused to increase in γ-tocopherol content, respectively while its content decreased up to the end of roasting time (40 min). α-tocopherol content at both temperatures increased after 20 min, then decreased gradually as time passes. Results indicated that both time and temperature of roasting had a significant effect on α- and γ-tocopherol of four nuts. Although both of temperatures in our study significantly on increased vitamin E isomers at the start of roasting process, their contents decreased with increasing in roasting time. Maximum amount of both isomers were detected at 120 ºC after 30 min and at 150 ºC after 20 min.
Seyyed Mohammad Emam; Amirmohammad Rezaiepoor; Aboalfazl Foorginejad
Abstract
Introduction: Pistachio cereals are one of the most important products in the export sector. Therefore, accurate grading of pistachios is very important. By counting the number of pistachios in 100gr according to the national standard of Iran, this product is classified into three categories of large, ...
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Introduction: Pistachio cereals are one of the most important products in the export sector. Therefore, accurate grading of pistachios is very important. By counting the number of pistachios in 100gr according to the national standard of Iran, this product is classified into three categories of large, medium and small. Materials and methods: In this paper, the image of some pistachio cereals with different random size and shape was taken and stored in computers using the machine vision technique. Then, the image processing operations consisted of improving the pistachio images to increase the accuracy of edge detection was done. The exact calibration process was performed with a chessboard plate was conducted to extract the geometrical dimensions including the largest diameter and area. In the national standard of Iran, intact or broken pistachios are not considered to grade this product. Therefore, in this research, Fourier series method is used to extract morphological characteristics of pistachio cereals including roundness, elongation, asymmetry, triangularity and squareness using the low order descriptors. According to the results of the calibration operation, the dimensional measurement of pistachios with an average error of 0.09 mm is possible Results & Discussion: According to the experimental results, it is possible to improve the current standard of pistachio using image processing and fourier series techniques in terms of increasing measurement speed, reducing costs, and adding the shape characteristics of pistachios to determine the amount of intact or broken pistachios.
Nasim Pourebrahim; Masoud Yavarmanesh
Abstract
Introduction:Pistachio nut is one of the popular tree nuts. Among the different species of the genus Pistacia, only the fruits of Pistacia vera attain optimal size to be acceptable to consumers as edible nuts. Contamination of pistachio by Aspergillus species and their mycotoxins is the most important ...
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Introduction:Pistachio nut is one of the popular tree nuts. Among the different species of the genus Pistacia, only the fruits of Pistacia vera attain optimal size to be acceptable to consumers as edible nuts. Contamination of pistachio by Aspergillus species and their mycotoxins is the most important problem for consumption and export of this product. Aflatoxins are potent toxic, carcinogenic and mutagenic secondary metabolites primarily produced by two fungal species, Aspergillus flavus and Aspergillus parasiticus. Aspergillus flavus produces AFB1 and AFB2, while Aspergillus parasiticus produces AFB1, AFB2, AFG1 and AFG2. Among four main groups of aflatoxins, AFB1 is the most potent carcinogenic compound. Therefore, identification of toxigenic fungi is necessary for evaluating the foods quality and the presence of mycotoxins. The current methods being used for assessing fungi presence in foods based on cultivation methods and microscopic characteristics are time-consuming and labor-intensive. Recently, molecular techniques such as polymerase chain reaction (PCR) due to high sensitivity, specificity and rapidity has been introduced as powerful tools for detecting toxigenic fungi. Many genes involved in the biosynthesis of these mycotoxins have been identified and their DNA sequences have been published. PCR methods can be used to detect of aflatoxigenic Aspergilli based on structural genes (nor1, ver1 and omtA) encoding key enzymes in aflatoxin biosynthesis pathway and the regulatory gene aflR.
Materials and method: Pistachio samples were collected from different cultivation regions of two towns including Gonabad and Feyzabad. Samples were packed in sterile plastic bags and immediately transferred to the laboratory. The moisture content of samples was determined using thermal method and drying in at 95-100°C. Among fungal isolates 30 Aspergillus genus were detected and purified by cultural-based methods using PDA (potato dextrose agar) medium. Colonies of the fungus were transferred to PDB (potato dextrose broth) medium and incubated for 5 days at 28°C with shaking at 150 rpm. The mycelium was frozen in liquid nitrogen and ground to a powder for later DNA isolation. DNA was extracted with CTAB (cetyl trimethyl ammonium bromide) extraction buffer, then was purified with organic solvents such as chloroform/isoamyl alcohol and finaly was precipitated by isopropanol. Aspergillus genus were detected using polymerase chain reaction by specific primer pair Asp1/Asp2 for amplification of 18S rRNA region. Furthermore, aflatoxigenic genes were detected by three sets of primers (APA-450/APA-1482, ver1/ver2 and OMT-208/OMT-1232). PCR was performed in a volume of 25 µl containing 0.5 µl of each primer, 12.5 µl of Taq DNA polymerase master mix red, 10.5 µl of sterile distilled water and 1 µl of genomic DNA as template. A PCR consisted of an initial denaturing step of 5 min at 94°C followed by 35 cycles (30 s at 94°C, 35 s at 65°C and 40 s at 72°C) finished by a final extension step at 72°C for 10 min. The PCR products were analyzed by electrophoresis on a 1% agarose gel in TBE.
Results and Discussion: Among fungal isolates 30 Aspergillus genus were detected using microscopic characterstics and colony color. Under the microscope, conidia were one-celled, spherical, hyaline or pigmented and they formed long chains. 12 and 4 out of 30 samples had omtA and ver1 genes respectively. No observation was found for aflR regulatory gene in the fungal isolates. The results showed that although some isolates had one or two structural genes in the aflatoxin biosynthetic pathway, they could not produce aflatoxin due to not having any aflR gene. Coefficient of correlation was calculated to find the relationship between the existence of Aspergillus molds and aflatoxigenic genes in pistachio. The statistical results indicated that there is a significant correlation between the enumeration of Aspergillus molds and the existence of genes (omtA and ver1) in different moisture domains (p> 0.05) while no significant correlation was identified between the enumeration of Aspergillus molds and the existence of genes in different domains of enumeration of mesophilic bacteria, yeasts and molds. Contamination of nut seeds by fungi occurs during growth, harvesting, transport and storage. The production of aflatoxin is affected by different factors, such as genetic properties of the producing fungi, temperature, moisture content, the chemical composition of food and antimicrobial agents produced by other microorganisms. Water stress and temperature are the most relevant environmental factors which influence fungal growth and mycotoxin production. Other studies showed that there was a good correlation between the expression of an early structural gene (aflD) and aflatoxin B1 production in peanut seeds. Also previous studies have shown that there was a significant relationship between A.flavus contamination in the peanuts and pistachio with high humidity (p> 0.05). Since other factors such as temperature, pH and chemical composition of pistachio can affect the existence of Aspergillus molds and expression of aflatoxigenic genes, the influence of these factors on existence of Aspergillus molds and genes involved in aflatoxin biosynthesis pathway need to be investigated.
