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Some Factors Causing Rice Milling Loss in Bangladesh

N.N. Sarker
Associate Professor
Dept. of Farm Power and Machinery, Bangladesh Agric. Univ., Mymensingh, Bangladesh

Shah M. Farouk
Professor
Dept. of Farm Power and Machinery, Bangladesh Agric. Univ., Mymensingh, Bangladesh

Abstract/ Executive Summary:

Among all operations performed in harvest and post-harvest processing of rice, major losses occur during milling. With a conservative loss estimate of only 6% duringthe milling process, Bangladesh has a chance of losing rice of worth about US$170 million annually. From a study on some rice mills in the Mymensingh district of Bangladesh, it was observed that inadequate parboiling treatment, development of fissure in the grains, and the nature of milling equipment used were some important factors responsible for losses during milling: an individual grain may lose as much as about 25% of its head rice weight if broken during milling; and the major loss occured immediately after breakage of grains when the broken parts with sharp edges were subjected to rounding and smoothening actions as they moved onward by rolling through the milling chamber before being finally discharged as milled rice. Restricted degree of milling and introduction of a set of standards for milling equipment and the procedures are suggested as means of reducing the milling loss of rice.

Keywords: Milling Equipment, Parboiling Treatment, Fissures in Grains

Location: Mymensingh

Start Date:

End Date:

Program Area: Farm Mechanization

Commodity: Performance evaluation

Objectives:

To findout the causing rice milling loss in Bangladesh

Methodology:

Five large rice mills with individually operated parboiling facilities situated in the industrial estate of Mymensingh and three others at Tarakanda, a well known rice producing area north of Mymensingh were visited to collect information on rice milling technology. Rice samples were collected from three of these rice mills. Another set of rice samples were collected from three small rice mills in Bhaluka south of Mymensingh. These small rice mills do not have parboiling facilities to which individual farmers bring parboiled paddy in lots of about 50 to 100 kg at a time for milling. Rice varieties readily available in the mills were selected for this study in order to avoid the difficulty of getting an intended variety at a selected rice mill. A pre-designed questionnaire was used in collecting information on soaking and steaming duration, additive uses in soaking water, milling capacity and milling yield. Physical dimensions of rough rice, brown rice and milled head rice were measured with a screw gauge. Weights of 1 000-grain samples of rough and milled head rice were measured with an analytical balance (The terms rough rice (paddy), head rice and milled rice used here are in conformity with the American and Japanese usage). Data on actual milling output were obtained from the millers and were expressed in percentage of rough rice fed for milling. Expected milling output was determined at the laboratory by taking the weights of I 000-grain of milled head rice and the corresponding weight of I 000 grain of rough rice and then expressing the weight of milled head rice as a percentage of the weight of the rough rice. Any shortfall in actual milling output from this expected milling output was considered as the milling loss due to breakage of grains. The broken grains were separated from the head rice of a sample with a tray grader. The number of broken grains in a sample was determined by weight analysis. Loss due to the breakage of single grain was determined by dividing the loss in weight of milled rice (milling loss) by the number of broken grains. This loss was finally converted to percentages of single milled head rice weight. Fissures that developed in the grain were determined by visual observation after hand shelling of the rough rice and were expressed as a percentage of the total grains tested. This crack counting test was performed after a few days of the sample collection when the possibility of further crack generation had ceased.

Source of Information: AGRICULTURAL MECHANIZATION IN ASIA. AFRJCA ANE LATIN AMERJCA 1989 VOL.2O NO.2

Article Link (Online Journal):

Funding Source:

Total Budget (Tk.) :

Achievement/Findings:

The use of single steam PiPe for steaming rough rice was inadequate for uniformly parboiled rice. Improvements in the steaming equipment design should help mini' mize milling losses from brqakage and surface scouring of rice resulting from non-uniform parboiling.
Due to continued mechanical stresses on grains the breakage percentage was found to exceed the percentage of fissured grains in a sample.
Individual grains were found to lose as high as about 25% of its head rice weight if broken during milling. However, this depended on the amount of smoothening and rounding actions imparted on the broken parts as they rolled through the milling chamber.
The average rice loss due to breakage was 3.66 kg of milled rice per 100 kg rough rice fed for milling.
Restricted degree of milling tended to increase the milling yield and of retaining more nutrients in the milled rice.
A set of standards regarding the degree of milling and the selection of parboiling and milling equipment are necessary for improving the performances of the rice-processing industry in Bangladesh.

Knowledge Management: Journal