Trade term
The maturity ratio, and what a rising number hides
The ratio divides soluble solids by titratable acidity, so it describes the balance between the two rather than either alone. It climbs through the season, and it can climb because sugar rose or because acid fell. Those are different fruits arriving at the same number on your specification.
The figures
| How it is calculated | Soluble solids divided by titratable acidity |
|---|---|
| Direction through the season | Rises as the fruit matures |
| What moves it | Either term can change independently |
What it changes on an order
You set a minimum ratio
Ask for both numbers behind it. A ratio met by collapsing acid late in the window is a different purchase from one met by sugar accumulating on time.
You buy at the end of a window
Late fruit tends to arrive at a high ratio with low acid, which reads flat rather than sweet. If your customer expects bite, say so.
You are comparing varieties
A ratio is comparable within a variety far more safely than across two, because the acid curves differ.
What this note does not settle
- We do not publish a measured ratio for our fruit. It sits in the pending fields of every variety datasheet.
- A ratio is a laboratory number from a juice sample, so it describes the fruit that was squeezed and not the pallet it came from.
A ratio climbs when the acid falls
Divide the soluble solids by the titratable acidity and you have the number the trade calls ratio, or maturity index. Two things move it. Sugars rising push it up, and acid falling pushes it up just as hard, which matters because acid keeps falling while fruit hangs on the tree. Late fruit therefore arrives with a high ratio that it earned by losing something rather than by gaining anything. The figure is honest. What it describes is a balance, and a balance is reached from either side.
Work on citrus maturity indices then unsettles the number itself. Lots that reach the same ratio from different pairs of readings score differently with tasting panels, which is why an alternative index that subtracts a weighted share of the acid instead of dividing by it has been proposed in the literature. Nobody in the trade buys on that index. What it tells a buyer is that a ratio decides when fruit is ready to pick, and stops well short of promising how the fruit will taste.
The same word, a different floor for each species
A minimum sugar to acid ratio is fixed in the marketing standard species by species, and the figures differ. Clementines sit above satsumas and below the other mandarin hybrids, while every orange in the table clears at the same number as a satsuma. One mixed order therefore carries two legal thresholds, and the clementine line is the harder of the two to meet with fruit that looks identical on the pallet.
The regulation also says how the number is arrived at, by pointing to the OECD guidance on objective tests rather than leaving the method to whoever holds the burette. That reference is the part worth borrowing. Name the method in your specification, name the acceptance figure, and attach a delivery week, because a ratio agreed for December and the same ratio accepted in April describe fruit that spent four extra months on a tree losing acid. Our own measurements are pending with the grower.
Talk to the grower
Tell us the variety, the sizes and the delivery week you need. You get a delivered price and what we can commit to in writing, from the person who picks the fruit.
The grower handles enquiries. Response times are still to be confirmed.