An E1 1cm saffron reading is an absorbance value, not a percentage and not a score out of one hundred. It tells you how strongly a standardised saffron solution absorbs light at one specific wavelength. Read at 440nm it describes colouring strength; at 257nm, bitterness; at 330nm, aroma compounds.
The notation looks forbidding because it is borrowed wholesale from analytical chemistry, where nobody was writing for shoppers. Once you take it apart, it is straightforward. This piece unpacks each element of it, then shows what the finished numbers can and cannot tell you about a batch.
What does the notation actually stand for?
Written out in full it is E1%1cm, and it has three parts.
- E is extinction, the older term for absorbance — how much light a solution swallows rather than lets through.
- 1% is the reference concentration the value is normalised to: notionally one gram of material in one hundred millilitres of solvent.
- 1cm is the path length of the cell the light travels through. Double the path and you double the absorbance, so the path has to be fixed before the number means anything.
So the figure answers a precise question: if you made up a one percent solution of this saffron and shone light through one centimetre of it, how much would be absorbed? Fix the concentration, fix the path, and different samples become directly comparable.
Why is it not a percentage?
Because absorbance has no units. A crocin figure of 230 does not mean the saffron is 230 percent of anything, and it certainly does not mean 230 percent crocin, which would be impossible. The 1% in the notation describes the reference solution, not the result.
This trips up a lot of people, and some sellers are content to let it. A pack advertising “crocin 250” sounds like a purity claim. It is not. It is a measure of light absorption, scaled.
Which three numbers appear on a saffron report?
Three wavelengths are read from the same prepared extract, each standing in for a different compound family.
| Wavelength | Compound family | What it describes | Category I minimum under ISO 3632 |
|---|---|---|---|
| 440nm | Crocins | Colouring strength — how much golden colour a given weight delivers | 190 |
| 257nm | Picrocrocin | Bitterness, the hay-and-honey base of saffron taste | 70 |
| 330nm | Safranal | Volatile aroma compounds | 20, with an upper limit of 50 |
Note that safranal is the one figure with a ceiling as well as a floor. More is not better. Exact limits are defined by the current edition of the standard, published as ISO 3632-1, and figures have shifted slightly between editions — the standard itself is the authority, not a table on a website, including ours.
How is the reading produced?
In outline, and without the parts that need a laboratory to appreciate:
- A weighed sample of dried saffron is ground to a fine, even powder.
- The powder is extracted into water under controlled conditions, then diluted to a fixed volume.
- A spectrophotometer measures absorbance at each of the three wavelengths.
- The raw absorbance is scaled by the mass used and corrected to a dry basis, so that moisture in the sample does not inflate or deflate the result.
Step four is the one worth remembering. Because the figure is reported on a dry basis, wet saffron cannot fake a high reading — but it can still cheat you on the scales, which is a separate problem entirely.
What counts as a strong crocin figure?
Under the standard, Category I begins at 190 at 440nm. Good commercial saffron often sits somewhere above that, and the best batches go higher still. Numbers in the 240 to 270 range appear on genuine reports and are not unusual for carefully harvested, well-dried, all-red saffron.
Two cautions. First, an unusually high figure with no report attached is a marketing number, not a measurement. Second, colouring strength is a single dimension. A batch can read high at 440nm and still be dull in the mouth if picrocrocin is weak, or stale if it has been sitting in a warm warehouse. The three figures are read together. Our walkthrough of how to read a saffron lab report takes a full document line by line.
What can the number not tell you?
Quite a lot, and this is where the notation gets over-sold.
- Origin. Absorbance says nothing about where a crocus grew.
- Adulteration with dye. A colourant that absorbs near 440nm can lift the reading. Detecting that takes different methods, not a higher number.
- Freshness. Safranal can rise before it falls during storage, so the aroma figure is not a clean age indicator.
- Which batch you received. A report describes the sample submitted. If the batch number on the report does not match the batch in your hand, the document is decoration.
That last point is the one we take most seriously. Our own analysis is underway and the full report will be published on our lab report page, batch number included, rather than summarised into a single flattering figure.
How does this fit with grades and categories?
The E1 1cm readings are the raw measurements. Categories are the buckets those measurements fall into, and grade names such as Super Negin or Sargol describe how the threads were cut, not how they performed in a spectrophotometer. The three ideas are constantly conflated in retail listings. We separate them in ISO 3632 explained in plain English and in the breakdown of Category I, II and III.
Frequently asked questions
Is a higher E1 1cm number always better?
For crocin at 440nm, higher generally means more colouring strength per gram. For safranal at 330nm it does not, because the standard sets an upper limit as well as a lower one. Very high aroma readings can point to over-drying rather than quality.
Does an E1 1cm figure prove the saffron is pure?
No. It measures how much light an extract absorbs. A dye that absorbs at a similar wavelength can raise the reading, so purity has to be established by other tests. Treat colouring strength as one piece of evidence, not a verdict.
Why do some reports show different numbers for the same batch?
Sample preparation, grinding fineness, moisture correction and the age of the sample all move the result. Two honest laboratories can return figures that differ by a few points. Large gaps are a reason to ask questions.
Can a home cook measure colouring strength?
Not properly. It needs a spectrophotometer and a controlled extraction. At home you can compare two saffrons by blooming equal weights in equal volumes of warm water and looking at them side by side, which is useful but not a measurement.
