How to Measure and Improve Milling Recovery in a Rice Milling Operation
Milling recovery is the most important performance number in a rice milling operation. It is the percentage of total white rice you extract from paddy input, and within that, the percentage that is head rice — whole, unbroken grains that command the full market price. A well-configured and well-operated line on clean, correctly moisturised paddy should achieve total white rice recovery of 67 to 72%, with head rice of 60 to 66% of paddy input. If your numbers are lower than this, you are losing revenue every day the line runs. This guide explains how to measure milling recovery correctly and what to adjust to improve it.
What milling recovery means and why it matters
Milling recovery is expressed as the weight of output divided by the weight of paddy input, as a percentage.
Total milling recovery = (total white rice out) ÷ (paddy in) × 100%
Head rice recovery = (head rice out, unbroken grains only) ÷ (paddy in) × 100%
The two numbers measure different things. Total recovery tells you how much white rice you are producing from a given paddy input. Head rice recovery tells you how much of that white rice is commercially valuable whole grain, as opposed to brokens and meal.
Brokens — broken grain fragments — typically sell at 40 to 65% of the price of head rice, depending on the market. Meal and flour (very small fragments) sell at commodity grain or animal feed prices. The revenue difference between a line producing 60% head rice and 50% head rice from the same paddy input, at typical market price differentials, is significant over a season.
A typical reference range for a well-operated commercial line processing standard long-grain Indica paddy:
- Total white rice recovery: 67 to 72%
- Head rice recovery: 60 to 66%
- Brokens: 4 to 8%
- Meal and dust: 1 to 3%
- By-products (bran): 6 to 9%
- Husk: 20 to 22%
If your operation is below these reference numbers, there is a specific, diagnosable cause. The following sections explain how to find it.
How to measure milling recovery correctly
Accurate milling recovery measurement requires a controlled test run, not an estimate from daily production records.
Start with a precisely weighed batch of paddy — 100kg is a practical test quantity for most operations. Record the paddy weight and its moisture content at milling. Run the batch through the complete line.
Weigh each output stream individually: head rice, brokens, meal, bran, husk. The sum of all outputs should be close to the input weight (some moisture is lost as steam during polishing, so slight weight reduction is normal). If the total output weight is significantly below input weight, check whether any collection point in the line is losing material.
Head rice must be separated from brokens in the output. Most lines produce a graded output from the rice grader that already separates head rice from brokens. If the grader is not in the line, use a sample screen to separate whole grains from fragments and weigh each fraction.
A single test shows you performance at that moment with that input. Running the test on several batches from different paddy sources and at different times in the season shows you how consistent your recovery is and whether specific paddy supplies are producing lower recovery numbers.
What causes low milling recovery: a diagnostic checklist
High paddy moisture above 15% causes elevated brokens at the husker and whitener. Check moisture at intake. If paddy is arriving wet, the first intervention is drying before milling, not adjusting machine settings.
Paddy below 12% moisture is brittle. It fractures at the husker regardless of how carefully the gap is calibrated. If paddy has been stored for a long period in dry conditions, check moisture before milling. Conditioning the paddy with a light water spray and a 12 to 24 hour tempering period can restore some elasticity.
A husker roll gap that is too tight crushes the grain and produces brown rice breakage at the first stage. A gap that is too wide fails to deshusk efficiently, requiring more re-processing passes through the husker. Calibrate the gap to the correct setting for your grain variety, check after roll replacement, and check if the variety changes.
Worn husker rolls reduce husking efficiency and increase the amount of paddy remaining in brown, requiring more re-processing passes. More passes through the husker increase cumulative breakage. Check roll diameter against the minimum specification and replace when due.
Over-milling — running the whitener at too high a pressure or for too long — removes more than the bran layer. It removes part of the endosperm, producing a chalky, over-milled grain with elevated brokens. Check degree of milling by measuring bran removal weight and comparing to the 8 to 10% target. If bran removal is above 12%, reduce whitening pressure.
Running a single whitening pass at high pressure to achieve the full degree of milling in one stage produces more breakage than two passes at moderate pressure. If your line has a single whitening stage and breakage is high, the structural fix is a second whitening pass. Two-pass whitening distributes the milling work, reduces grain stress per pass, and produces lower brokens for the same output whiteness.
Stone and metal fragments that survive the pre-cleaning and destoning stages cause mechanical damage to rolls and to grain at every downstream stage. A single stone particle passing through the whitener can fracture multiple grains and score the whitening roll surface. Pre-cleaning effectiveness directly protects downstream milling recovery.
Roll gaps, screen tensions, and paddy feed rates change over time with wear and vibration. A machine calibrated correctly at commissioning may have drifted after months of operation. Scheduled calibration checks (roll gap measurement, screen inspection, feed rate verification) prevent drift from accumulating into significant recovery losses before it is noticed.
The milling recovery log: a practical tool for every operation
The most practical recovery improvement tool for a commercial milling operation is a simple daily logbook that records:
- Date
- Paddy source and variety
- Paddy moisture at intake
- Paddy input weight for the production period
- Head rice output weight
- Brokens weight
- Total recovery % and head rice %
When recovery deteriorates, the log shows exactly when it started and what changed in the input conditions. This narrows the diagnostic effort significantly. When recovery improves after an adjustment — roll replacement, gap recalibration, moisture correction — the log confirms the improvement is real and quantifies the benefit.
A logbook kept consistently for a season gives you the baseline recovery performance for your specific paddy supply and your specific machines. This baseline is the number you manage against. Without it, you are diagnosing recovery problems without the data to find the cause.
Frequently asked questions
What is a good head rice percentage to aim for?
For standard long-grain Indica processing in good operating conditions — paddy at 13 to 14% moisture, correct roll calibration, two-pass whitening — head rice recovery of 60 to 66% of paddy input is the reference range. Short-grain Japonica, which has a rounder, more robust grain, can achieve slightly higher head rice percentages under the same conditions. Long-grain Basmati, which is the most fragile variety at milling, may achieve 55 to 62% head rice under optimal conditions. Parboiled rice achieves similar or slightly higher head rice than raw Indica because the gelatinised grain structure is more resistant to fracture during whitening.
Can milling recovery be improved by adjusting the machines alone?
Machine calibration improvements can recover percentage points of head rice that are being lost to incorrect gap settings or over-milling, and these adjustments should be made. But if paddy is arriving at the mill at 17% moisture, no machine adjustment produces the same recovery as milling at 14%. The variables that matter most for recovery are paddy moisture (controlled by drying), paddy cleanliness (controlled by pre-cleaning), and grain variety — all upstream of the milling machines themselves. Machine calibration is the second layer of control, not the primary one.
How does head rice recovery affect profitability?
If head rice sells at $500 per tonne and brokens sell at $300 per tonne, a 5 percentage point improvement in head rice recovery on a 20 TPD line — turning 5% of paddy input from brokens to head rice — produces approximately 1 tonne per day of additional head rice output at a price premium of $200 per tonne over brokens. Over a 200-day milling season, that is $40,000 in additional margin from a 5% recovery improvement. The exact numbers vary by market, but the direction is clear: every percentage point of head rice recovery has a direct, calculable revenue value.
Improve your milling line's recovery
Browse All Rice Milling Machines