اثررطوبت، سرعت دوراني و مدت زمان بارگذاري بر قابليت شكست دانه برنج با كمك دستگاه آزمون گريز از مركز بهينه سازي شده

Effect of moisture contant, rotational speed and duration of test on breakage susceptibility of rice bulk sample by a modifieid centrafugal tester

چكيده براي تعيين علل كاهش استحكام دانه هاي برنج طي عمليات برداشت و پس از برداشت و نيز امكان مقايسه كيفيت توده برنج،به ويژه در مراحل خريد و فروش،وجود روش و ابزار مناسب براي اين كارضروريست. يكي از اين معيارها شاخص قابليت شكست توده دانه مي باشد كه مي توان آن رابا آزمايش نمونه توده دانه توسط يك دستگاه گريز از مركز ضربه اي اصلاح شده به صورت درصد وزني مشخص نمود. براين اساس، با انجام اصلاحاتي بر روييك دستگاه آسياب آزمايشگاهي، در يك طرح آزمايشي كاملا تصادفي به شكل فاكتوريل (با انجام 500 آزمون) اثر محتواي رطوبتي، سرعت دوراني تيغه و مدت زمان كار دستگاه بر عملكرد دستگاه بر اساس ايجاد 50%شكستدر توده دانه مورد بررسي قرار گرفت. نتايج حاصل از آزمايشات نشان داد كه هر سه عامل مورد بررسي اثري كاملا معني دار بر شاخص قابليت شكست دانه داشتند. در نتايج حاصله مشخص شد كه سرعت 1000 دور بر دقيقه و كمتر از آن و سرعت 5000 دور بر دقيقه و بيشتر از آن براي انجام اين آزمايش به ترتيب به دليل شكست كم و شكست زياد مناسب نمي باشند.در نهايت سرعت 4000 دور بر دقيقه با رطوبت 9 درصد بر پايه ي تر با مدت زمان 80 ثانيه در محدودهشكست 23 تا 67درصد، به عنوان بهترين شرايط آزمون شناخته شد.

Abstract For determining the rationale of reducing strength of rice kernels during harvesting and postharvest operations and comparing the quality of rice bulk samples, specially for comercial proposes, a suitable device and method for rice quality measurment is necessary. Rice Breakage susceptible index for bulk samples, is a proposed index which could be determined by a centrifugal impact tester based on weight percent. Therefore, by modification of a laboratory mill, the effect of moisture content, blade rotational speed and duration of test were investigated on a fabricated apparatus performance, based on 50% breakage level and according to a completely randomize factorial test and by conducting 500 milling tests. The results showed that the three independent factors had a significant effect on BSI. According to the results, the speed of 1000rpm and less, and the speed of 5000rpm and more, are not suitable for this kind of test due to very low and very high rate of breakage, respectively. Finally, the speed of 4000 rpm, moisture content of 9% (wb) at 80 seconds of test duration was selected as the best condition for the test, according to 50% rate of breakage with minimum and maximum rate of 23 and 67%. Abstract For determining the rationale of reducing strength of rice kernels during harvesting and postharvest operations and comparing the quality of rice bulk samples, specially for comercial proposes, a suitable device and method for rice quality measurment is necessary. Rice Breakage susceptible index for bulk samples, is a proposed index which could be determined by a centrifugal impact tester based on weight percent. Therefore, by modification of a laboratory mill, the effect of moisture content, blade rotational speed and duration of test were investigated on a fabricated apparatus performance, based on 50% breakage level and according to a completely randomize factorial test and by conducting 500 milling tests. The results showed that the three independent factors had a significant effect on BSI. According to the results, the speed of 1000rpm and less, and the speed of 5000rpm and more, are not suitable for this kind of test due to very low and very high rate of breakage, respectively. Finally, the speed of 4000 rpm, moisture content of 9% (wb) at 80 seconds of test duration was selected as the best condition for the test, according to 50% rate of breakage with minimum and maximum rate of 23 and 67%.