Effect of moisture content on engineering characteristics of apricot (Prunus armeniaca L.) kernel

Apricot (Prunus armeniaca L.) kernels, the innermost part of the economical stone fruit, are utilized for edible purposes, extraction of oil, and many pharmaceutical products. Biological materials are complex in structure and get affected by their moisture content. This study investigates the effect of different moisture content from 5.66% to 26.47% wet basis apricot kernels on its various engineering characteristics and develops their correlations. The engineering characteristics such as linear dimension length (13.26-14.47 mm), breadth (8.69-9.97 mm), thickness (5.36-6.50 mm), arithmetic mean diameter (9.11-10.32 mm), geometric mean diameter (8.48-9.77 mm), surface area (227.91-302.68 mm(2)), projected area (91.99-114.95 mm(2)), 1000 kernel mass (0.317-0.403 kg), true density (881.23-973.55 kg m(-3)), and porosity (33.74%43.68%) increased linearly with moisture content. On the other hand, bulk density (548.23-583.89 kg m(-3)) and elongation ratio (2.25-2.51) showed a decreasing trend with an increase in moisture content. The frictional properties such as angle of repose (22.81-28.92 degrees) and coefficient of static friction value for glass, stainless steel, galvanized iron, and wood were found to increase with increased moisture content and ranged from 0.179-0.283, 0.272-0.347, 0.416-0.512, and 0.488-0.595, respectively. The highest static coefficient of friction was observed for wood surfaces. A significant difference in color values L*, a*, b*, hue angle (H), chroma (C), and Delta E values were observed at different moisture content. Terminal velocities and hardness of AK increased linearly with moisture content and the values were found between 4.26 and 5.91 m s(-1) and 21.59 to 35.25 N mm(-1), respectively.