عنوان مقاله [English]
نویسنده [English]چکیده [English]
Introduction The hazelnut (Corylus avellana L.) is one of the most cultivated and consumed nuts in the world, not only as a fruit but also as a main constituent into a wide range of manufactured food products. Iran after Turkey, Italy, USA, Azerbaijan, Georgia and China, is the world's seventh largest producer of hazelnuts. Guilan province is the largest producer of hazelnuts in Iran. More than 90 percent of hazelnut of this province, after removing the initial green shell is sold at low prices. Therefore, design and optimization of harvesting machines and processing equipment to produce this product is important. Thus, the aim of this research was to study the physical, mechanical and nutritional properties of three common hazelnut cultivars in Guilan province of Iran.
Materials and Methods In this study, two common local cultivars of hazelnut in north of Iran (Gerd and Badami), and an improved variety namely Keshavarzi were considered for all experiments. Experimental samples were supplied from Eshkevarat region as the major hazelnut producing part of Guilan province. All physical, mechanical and nutritional properties of both the hazelnut and kernel samples were measured and computed at moisture content of 2.3–3.3% dry basis.
Nutritional properties including crude protein, oil, crude fiber, ash, dry matter, carbohydrate and some minerals, i.e. N, P, K, Mn, Fe, and Zn contents of hazelnuts, were measured based on the standard methods. All nutritional and mineral data were analyzed through a completely randomized design with three replications.
Physical properties including dimensional properties, bulk and true densities, porosity, natural angle of repose, terminal velocity, and coefficient of friction on plywood structural surface and galvanized iron sheet were measured based on the standard procedures. All physical data were analyzed through a completely randomized design with five replications.
Mechanical properties including rupture force, deformation and energy absorbed at rupture point along with the hardness of nuts were determined by applying force to three major perpendicular axes of all nut samples. The energy absorbed for rupture nuts was determined by measuring the area beneath the strain-stress curves and hardness of nuts was computed as the ratio of rupture force to the corresponding value of deformation at rupture instant. All mechanical data were analyzed through a completely randomized design with five replications.
Results and Discussion According to the variance analyses, there were significant differences between the hazelnut cultivars in terms of crude protein and fiber, ash and carbohydrate contents (pStudy of the physical properties showed that there were significant differences among all dimensional characteristics of the hazelnut cultivars and their fruits. All dimensional characteristics of hazelnut cultivars were significantly higher than those of their fruits. All linear dimensions of Keshavarzi hazelnut cultivar were significantly more than those of local cultivars of Badami and Gerd, while there were no significant differences among length and width of Keshavarzi cultivar and Badami local cultivar.
Bulk density, porosity, dynamic natural angle of repose, terminal velocity, and static coefficient of friction on plywood sheet of the hazelnut cultivars were found to be statistically significant at five percent level and p<0.001, but there was no significant difference among true densities of cultivars. There were significant differences between values of bulk density, dynamic natural angle of repose, terminal velocities, and coefficient of friction on plywood structural surface, but no significant differences were seen for true density, porosity, and coefficient of friction on galvanized sheet. Differences among the majority of physical characteristics of hazelnut cultivars and their fruits can be used in design and adjustment of harvesting and processing equipment.
Different data were recorded for mechanical properties in various axes of all hazelnut varieties. In more spherical cultivars, the mechanical properties in three dimensional axes were close to one another. The data of rupture force, deformation and energy absorbed at rupture instant, and hardness of nuts can be used for design and adjustment of hazelnut crackers.
Conclusion There were significant differences between a large number of physical and mechanical properties of three common hazelnut varieties in Guilan province, Iran. The differences among the engineering characteristics should be used in design and optimizing of hazelnut machineries and processing equipment.
The results showed that the improved hazelnut cultivar of Keshavazi had no considerable superiority to landraces cultivars of Gerd and Badami in terms of nutritional and mineral contents. Therefore, it is essential that along with the physical superiority of alternative hazelnut cultivars, their nutritional and mineral advantages be considered by the agricultural experts in Guilan province, Iran.