Prediction of Stiffness of Different Orange Cultivars Using Punch Test Method (Case Study: Orange Cultivars in The Southern Region of Kerman Province)

The firmness of the orange texture can be considered as an important criterion for determining the quality and freshness of this product and its texture characteristics have a great influence on its acceptability and marketability. Orange is an important product in the south of Kerman province, having sufficient knowledge and information about its texture mechanics is also important for the development of orange industries and processing equipment, especially orange concentrate production industries. In response to need the mechanical properties of the orange texture, punch test method was proposed as a suitable and non-destructive testing method. In this research, firmness, force, stress and consumption energy of five common orange varieties (Valencia, March, Washington Navel, Blood and Local Jiroft) was determined and compared by punch test method with seven punch diameters (4.3, 4.6, 9.7, 9.5, 11.1, 12.7 and 14.3 mm). The results showed that the effect of variables of punch diameter, variety, and also the interaction effect of punch diameter × variety on the force, firmness, stress and energy were significant at 1% level. The combination treatment of local cultivar with a punch diameter of 12.7 mm has the maximum value of force (79.0 N) and firmness (7.9 N/mm), and the minimum value of force (15.5 N) and firmness (1.5 N/mm) was obtained in the combination treatment of blood variety and punch diameter of 4.8 mm. The highest mean of stress (1.5 MPa) and the lowest mean stress (0.3 MPa) were in the combination treatment of local variety and punch diameter of 4.3 mm, and the combination treatment of blood variety and punch diameter was 14.3 mm.