In this guide 6 sections
A falling extraction rate usually traces to the wheat lot, the tempering moisture or the roller settings. Compare each lot’s intake test with its tempering record and its output split of whole wheat flour, refined flour and bran. The lot where the split moves first points to the cause.
Read the output split before you touch a machine
Extraction is the weight of flour you get from the wheat you grind. When it slips, owners tend to blame the rolls first. Look at the split instead. Weigh whole wheat flour, refined flour, bran and offal for each lot and write them in one row. Both numbers matter.
A drop in refined flour with more bran points one way. A drop in total flour with more offal points another. Shrunken grain, bran that will not separate and weak sifting each leave their own signature in the split. A rough tally on a whiteboard beside the mill, updated after every lot, beats a monthly figure compiled from the office ledger. The wheat is long gone by then.
Do this by lot, not by week. Mixed weekly figures hide the one bad truck.
- Quantity ground per lot
- Whole wheat flour, refined flour, bran and offal weights
- Total recovered against total ground
- Date, shift and mill line
Wheat lot quality explains most sudden drops
Wheat from a new supplier, a new village or a different harvest week behaves differently on the same mill. Test weight, thousand kernel weight, broken and shrivelled grain, foreign matter and gluten content all change what the rolls can recover. Ask the buyer for the test report before the truck is unloaded. A late complaint cannot be traced back to a field or a trader once the silo is mixed.
Light, shrunken wheat carries more husk per kilogram, so less endosperm is available. Wheat with a high share of damaged or sprouted grain will mill soft and sticky and clog the sifters. These are intake problems, and they are visible before grinding if somebody tests and records them. Keep a retained sample of every lot in a labelled bag for a few weeks, so that a surprising result can be tested again against the grain itself.
Tag each lot with a number at the weighbridge and keep that number through the silo and the cleaning house.
Tempering moisture decides how the bran comes off
Water added before milling toughens the bran and mellows the endosperm. Too little and the bran shatters into small flakes that pass into the flour as specks. Too much and the stock turns pasty, the sifters blind and throughput falls. Moisture is the lever.
Record the starting moisture, the water added, the resting time in the bins and the moisture at first break. Hard wheat and soft wheat want different rest times, so one standard setting across every lot will hurt some of them. Rest time is a setting too.
Check the dampening machine too. A worn dosing pump gives the same dial reading and a different real flow. Ten minutes with a bucket and a stopwatch tells you the truth.
- Incoming grain moisture by lot
- Water added and resting hours
- Moisture at first break
- Dampener flow check date
Roller gaps, sifter cloth and flow rates
Once wheat and moisture are cleared, look at the machine. Break roll gaps open as corrugations wear. Smooth rolls lose grip. A pass that was set well in spring may be loose by monsoon, particularly if the feed rate has crept up to hit a daily target. Rolls wear quietly, and a mill that never records a gap adjustment cannot say whether the drop began on a Tuesday or in the last quarter.
Torn or stretched sifter cloth lets bran dust into refined flour, so the lab may downgrade the lot. Blocked cloth does the opposite and sends good flour to the bran stream. Check purifier air and the feed on each passage.
Keep a log of every roll change and gap adjustment against the date. It turns a guess into a pattern. Make that log part of the shift handover so the next team inherits it.
Build a lot by lot record you can compare
Put intake tests, tempering readings, machine settings and the output split in one record per lot. A spreadsheet works for a month or two. After that, linked lots, shift handovers and several mill lines are easier in a system built around milling. Whichever tool you pick should link the weighbridge ticket, the intake test and the mill output. Nobody should retype a lot number three times.
Compare the best ten lots with the worst ten. The differences will usually be few and obvious, such as one supplier, one moisture setting or one roll that was not changed. Patterns appear fast.
Begin tomorrow with a simple card on the weighbridge. Write the lot number, test weight and moisture, and carry it to the mill floor.
Lot extraction record sheet
Each wheat lot gets its own row on this sheet. Columns cover supplier, test weight, moisture, broken grain, tempering water and rest hours, first break gap and sifter check. The right side holds output weights for whole wheat flour, refined flour, bran and offal, then extraction and the likely cause.
Open a blank worksheet to printQuestions owners ask
How often should extraction be calculated?
For every lot, and again for each shift. Weekly totals hide the single bad truck or the one worn roll that caused the fall.
Can moisture alone explain a drop?
It can, but check the wheat first. Hard wheat with too little water breaks bran into flakes, and soft wheat with too much clogs sifters. Compare moisture readings with the output split.
Do roller settings matter if the wheat is good?
Yes. Worn corrugations and drifting gaps change how much endosperm is scraped from the bran. Log each adjustment with a date.
Is a spreadsheet enough to track this?
For one line and a few lots a day, yes. Software helps when lots, shifts and lines multiply and the comparison takes longer than the milling.