This study aimed to extend the shelf life of walnut kernels by appropriate packaging conditions and physical methods. For this purpose, the kernels were heated at 50 or 70°C for 2 or 10 minutes. About 100g of walnuts were packed in low-density polyethylene (LDPE) packages under ordinary, vacuum or nitrogen conditions. Samples were stored for 18 months at room temperature. Peroxide value and acidy number were determined after 6, 12 and 18 months of storage. The results of the variance analysis showed that the effect of packaging conditions on peroxide value, and the effect of all factors on the acidity of the samples were significant (p < 0.01) for the 6- month storage. Walnuts packaged under nitrogen conditions had lower peroxide value than others, and the samples preheated at 70˚C had a lower acidity. After 12 months of storage, the effect of all factors on peroxide and the acidy number of walnuts were significant (p < 0.01). The lowest peroxide value and acidity were observed for walnuts preheated at 50˚C for two minutes. Finally, based on the obtained results, we recommend that walnut kernels should be preheated at 70˚C for two minutes and packaged under nitrogen or vacuum conditions. In this way, they could be stored for six months without perceived oxidation. The oxidation of walnuts would increase during storage for 12 to 18 months gradually, and their peroxide value and the acidity would exceed the desirable limits. تفاصيل المقالة

The study was performed to investigate the Aspergillus growth and aflatoxin production in fresh pistachios stored in different packagings. Forty kg of fresh pistachios of the Abbasali cultivar were sampled and kept in different temperature conditions including 4°C and ambient conventional temperatures in plastic baskets or polyethylene plastic bags. Sub-samples were taken at 4 days intervals for 32 days to measure aflatoxin and evaluate the population of Aspergillus section Flavi. Aflatoxins were quantified by HPLC and the fungal population was monitored by dilution series method and AFPA medium. The results showed that on the first day of storage in all conditions the amount of aflatoxin was undetectable. Aflatoxin infection started on the fourth day after storage in the ambient conventional temperature and increased over time. The lowest production of aflatoxin B1 was in the 4°C treatment. Pistachios stored at ambient conventional temperature and packed in plastic baskets showed the highest amount of aflatoxin B1 production. The effect of the treatments on the production of aflatoxin B1 showed that the samples in polyethylene plastic bags at ambient temperature were the highest. The results showed that in the 4°C treatment, the fungal population was significantly less than in ambient temperature treatments. The lowest fungal population was in the 4°C plastic baskets packaged treatment. This treatment was not significantly different from the 4°C polyethylene bag treatment but was significantly different from other treatments (P≤0.01). In general, keeping fresh pistachio at 4°C and suitable plastic is trustworthy. Storage for more than 8 days in the ambient conventional temperature greatly increases the risk of fungal and aflatoxin contamination. تفاصيل المقالة

Roasting has considerable effects on the quality of cream made of nuts. In this study, the roasting conditions of walnut kernels were optimized based on the stability parameters of the produced cream. Temperatures of 100-150°C for 10-30 minutes were used to roast walnut kernels. The amount of oil separation, peroxide, acidity and Thiobarbituric acid values of the cream, as well as color parameters were determined after three months of storage at 25°C. The results showed that the oil separation increased with temperature and time of roasting (from 4.16% at 100°C/10min to 7.85% at 150°C/30min). Peroxide, acidity and thiobarbituric acid values were significantly affected by temperature and time of roasting. In addition, it was shown that as the temperature increased, the redness and yellowness increased, but the lightness of the samples decreased. Finally, the temperature of 116°C for 12 minutes was chosen as the optimized roasting conditions for producing walnut cream. تفاصيل المقالة

The issue of contamination of pistachios with Aspergillus flavus and aflatoxin is a serious and important threatto the production, export and consumption of pistachios worldwide. Investigating the resistance of pistachio cultivars to A. flavus and its relationship with the physicochemical characteristics of pistachio kernels can be considered as one of the main management strategies to deal address aflatoxin contamination. In this research, the resistance of six important pistachio cultivars to A. flavus and aflatoxin was first determined. The relationship between the thickness of the testa (the thin skin on the kernels) and the growth of A. flavus and aflatoxin production was then investigated. The testa of pistachio cultivars was inoculated using a toxin-producing isolate of A. flavus. Eight days after inoculation, the growth and colonization rate of the fungus was measured and evaluated using the Kernel Screening Assay (KSA) method and the amount of aflatoxin determined by the High-Performance Liquid Chromatography (HPLC) method. The thickness of testa was measured using a micrometer. To investigate the possible relationship between the thickness of testa and the growth of A. flavus and aflatoxin production, the correlation coefficient (r) was calculated. According to the results of statistical analysis, the cultivars Shahpasand and Ghaniabadi exhibited the lowest resistance to the growth of A. flavus. The research results indicated that there was no significant relationship between the amount of fungus growth and aflatoxin and the thickness of the pistachio kernel skin in different cultivars.It appears that the chemical characteristics of the pistachio kernel and kernel skin play a more important role in resistance to fungal growth and aflatoxin production. تفاصيل المقالة