MTV Exit Analysis
Overview of Rice Milling
Rice is harvested at moisture contents typically ranging from 13% to 22% (wet basis). Because these moisture contents are greater than those safe for long-term storage, rice is dried within a fairly short period after harvest to 12% to 13% moisture content before being placed in storage. Once dried, “processing” or rough rice into milled rice takes place throughout the year and consists of several operations.
After cleaning to remove foreign material, rough rice is hulled to produce brown rice. The hull represents approximately 20% of the mass of a rough rice kernel. Brown rice is usually milled immediately after hulling, removing the bran layers and germ by frictional and/or abrasive action. The bran represents approximately 10% of the original rough rice mass.
The remaining milled or “white” rice comprises head rice, defined as those kernels retaining three-fourths or more of their original length, and broken kernels. The milled rice yield (MRY) represents the mass of milled rice expressed as a percentage of the original dried rough rice mass. The typical MRYs range from 68% to 72%. Upon removal of broken kernels, only head rice remains. The mass of head rice, expressed as a percentage of the original rough rice mass, is defined as the head rice yield (HRY). Head rice yields can vary from 0 (all kernels are broken) to a theoretical maximum of approximately 70% (no kernels are broken). Milling quality is often expressed as a ratio of the HRY to the MRY.
PROCESS ANALYSIS
I. Process Flow Chart Diagram
1 paddy is dumped in the intake pit feeding the pre-cleaner
2
pre-cleaned paddy moves to the rubber roll husker
3
mixture of brown rice and unhusked paddy moves to the separator
4
unhusked paddy is separated and returned to the rubber roll husker
5
brown rice moves to the destoner
6
de-stoned, brown rice moves to the 1st stage (abrasive) whitener
7
partially milled rice moves to the
Rice is harvested at moisture contents typically ranging from 13% to 22% (wet basis). Because these moisture contents are greater than those safe for long-term storage, rice is dried within a fairly short period after harvest to 12% to 13% moisture content before being placed in storage. Once dried, “processing” or rough rice into milled rice takes place throughout the year and consists of several operations.
After cleaning to remove foreign material, rough rice is hulled to produce brown rice. The hull represents approximately 20% of the mass of a rough rice kernel. Brown rice is usually milled immediately after hulling, removing the bran layers and germ by frictional and/or abrasive action. The bran represents approximately 10% of the original rough rice mass.
The remaining milled or “white” rice comprises head rice, defined as those kernels retaining three-fourths or more of their original length, and broken kernels. The milled rice yield (MRY) represents the mass of milled rice expressed as a percentage of the original dried rough rice mass. The typical MRYs range from 68% to 72%. Upon removal of broken kernels, only head rice remains. The mass of head rice, expressed as a percentage of the original rough rice mass, is defined as the head rice yield (HRY). Head rice yields can vary from 0 (all kernels are broken) to a theoretical maximum of approximately 70% (no kernels are broken). Milling quality is often expressed as a ratio of the HRY to the MRY.
PROCESS ANALYSIS
I. Process Flow Chart Diagram
1 paddy is dumped in the intake pit feeding the pre-cleaner
2
pre-cleaned paddy moves to the rubber roll husker
3
mixture of brown rice and unhusked paddy moves to the separator
4
unhusked paddy is separated and returned to the rubber roll husker
5
brown rice moves to the destoner
6
de-stoned, brown rice moves to the 1st stage (abrasive) whitener
7
partially milled rice moves to the