حساسيت به كوفتگي سيب تحت بارهاي ضربه اي

چكيده انگليسي :

Susceptibility of apple to bruising under impact loading Ali Hossein Habibirad Ah habibirad@ag iut ac ir h habibirad@yahoo com May Department of Agricultural Machinery Engineering Isfahan University of Technology Isfahan 84156 83111 Iran Degree M Sc Language Farsi Supervisor Prof A Hemmat ahemmat@cc iut ac ir Advisors Dr S A Mireei samireei@cc iut ac ir Dr H Hashemolhoseini hamidh@cc iut ac ir Abstract According to FAO Iran is one of the most important apple producers in the world with annual average production of two million tons Furthermore based on FAO reports apple export by the country has had an increasing trend during recent years To preserve this trend and raise the income using mechanical equipments for harvesting transporting handling sorting and packing processes of apples is required Nevertheless these unit operations are performed manually in our country On the other hand apple is too delicate and preserving its quality during these processes is essential So researchers are endeavoring to find strategies to design these systems and decrease damages in both harvesting and post harvesting by studying the causes of mechanical damages Bruising is the most important mechanical damage to apples The majority of such damages is caused by dynamic forces resulting from impacts Therefore it is justifiable to investigate fruit behavior under impact In this study an impact test device specialized for free fall drop was fabricated The experiments were conducted in two ways In the first one after measuring the apple mass it was dropped from different heights on an aluminum plate equipped with a load cell and then the force time curve was recorded In the second method halved apples were stabilized on a rigid steel plate and then spherical impactors with different masses dropped on them from different heights The two methods were applied on two varieties Jonagold and Fuji harvested at three different dates The flesh stiffness near the impact area was measured for all apples using penetration test with a universal tension and compression testing machine The radius of curvature of the apple surface at the impact area was measured by a curvature meter before impact test Bruise volume and area of apples were measured hours after impact test by measuring their dimensions To study the effect of variety and harvest date on bruising the results were analyzed using a factorial experiment in a completely randomized design Analysis of variance and the mean comparison indicated that the effects of the variety harvest date and their interaction on bruise volume and area were significant P The results illustrated that Jonagold variety was more sensitive to damages caused by impact than Fuji ones With delayed in harvesting time the average bruise volume and area were generally increased Afterward the bruising threshold was obtained as the allowable falling height and initial energy of impact producing bruise area of less than mm The allowable falling height was calculated for the first second and third harvesting times which were respectively and cm for Jonagold apple and and cm for Fuji apple Furtheremore the allowable initial energy of impact was obtained for the first second and third harvesting times which were respectively and mJ for Jonagold apple and and mJ for Fuji apple Finally several multiple linear regression models were developed to predict bruise volume and bruise area of both Jonagold and Fuji in collision with flat plate and spherical aluminum impactor Keywords Apple Jonagold Fuji mechanical damage bruising impact stiffness bruise threshold PDF created with pdfFactory trial version www pdffactory com

حبيبي راد، علي حسين

حساسيت به كوفتگي سيب تحت بارهاي ضربه اي

جوناگلد , فوجي , آسيب مكانيكي , ضربه , سفتي , آستانه ي كوفتگي