The fruit register
Thirty-four fruits, each with its measured pH range, its sugars and its pectin class. Acid and pectin are kept apart, because a fruit can be short of one and rich in the other.
Acid levels in fruit decide two different things: whether a preserve will set, and whether it is safe to can in a boiling-water bath. Those are separate questions with separate thresholds, and a single “acidity” label answers neither well. The list below sorts every fruit by its measured pH, so the low acid fruits and the high acid ones fall out of the data rather than out of a habit.
Of the thirty-four fruits here, 14 are low acid, 9 are high acid and 5 sit in between. 6 have no measured pH in the sources used, and those are listed as not established rather than guessed at.
These 14 are the low acid fruits in this set: Apricot, Banana, Blackberry, Sour cherry, Sweet cherry, Clementine, Fig, Guava, Mango, Honeydew melon, Orange, Peach, Pear and Persimmon (Japanese). Low acid here means a measured upper pH above 4.0. It is the group that needs help to set, and the group that needs care when canning.
Two of the commonest questions land squarely in it. Is mango acidic? By measurement, only mildly at its sharpest and not at all when ripe: the range runs 3.40 to 4.80, which puts a ripe mango above the acid line. Are strawberries acidic? More than a mango and less than a plum, at 3.00 to 3.90, which is mildly acidic rather than low acid, and the reason strawberry jam usually sets on lemon juice alone while mango jam usually does not.
The high acid fruits are Cooking apple (tart), Blueberry, Gooseberry, Grape, Lemon, Lime, Plum, Quince and Rhubarb. Anything at or below pH 4.6 can be processed in a boiling-water bath; above it, the acid is not doing the preserving work and a pressure canner or added acid is required. On these figures the fruits whose measured range crosses that line are Apricot, Banana, Fig, Mango, Honeydew melon and Persimmon (Japanese).
This is also where a lot of published advice quietly goes wrong. A fruit can be very acidic and still make a poor preserve, because acid is only half of the mechanism.
Pectin levels in fruit chart badly against acidity, which is exactly why the two are in different columns here. Read the pectin levels in fruit chart below on its own terms: a fruit's position in it says nothing about where it sits on acid. 13 of these fruits are high in pectin, 7 are low, and 14 have no pectin class established in the sources at all.
The fruits high in pectin are the ones that gel on their own sugar and their own acid: quince, crabapple, cranberry, redcurrant, gooseberry and the citrus peels. The fruits high in pectin are worth knowing by name, because one of them added to a weak-setting fruit does the job that a packet of pectin otherwise does.
Rhubarb is the clearest case against a single column. It is among the most acidic entries in the register, pH 3.10 to 3.40, and its pectin is low. No amount of extra lemon will set it. Strawberry is the same story one step milder. Quince is the opposite: high acid and high pectin, which is why quince paste sets to a slab with nothing added.
Sugars are per 100 g of raw fruit. Set group follows the extension-service classification, where group 1 needs no help, group 2 usually needs a little and group 3 needs added pectin or acid. A dash of any kind means the figure is not established in the sources rather than zero.
The table can be sorted on any of its columns and narrowed to one group, so the fruits that set unaided, the ones short of pectin, the ones short of acid, or the ones whose range reaches past 4.6. Whichever way it is sorted, the fruits with no measured figure stay at the bottom rather than drifting to whichever end would make them look like a low reading.
| Fruit | pH | Acid | Sugars /100 g | Pectin | Set group |
|---|---|---|---|---|---|
| Lemon | 2.00–2.60 | High | 2.50 g | High | 1 |
| Lime | 2.00–2.80 | High | 1.69 g | High | not established |
| Grape | 2.80–3.00 | High | 15.48 g | High | 1 |
| Gooseberry | 2.80–3.10 | High | not established | High | 1 |
| Cooking apple (tart) | 3.33–3.33 | High | not established | High | 1 |
| Blueberry | 3.12–3.33 | High | 9.96 g | Low | 3 |
| Plum | 2.80–3.40 | High | 9.92 g | High | 1 |
| Quince | 3.12–3.40 | High | not established | High | 1 |
| Rhubarb | 3.10–3.40 | High | 1.10 g | Low | not established |
| Grapefruit | 3.00–3.75 | Medium | 6.98 g | High | 2 |
| Strawberry | 3.00–3.90 | Medium | 4.89 g | Low | 3 |
| Raspberry | 3.22–3.95 | Medium | 4.42 g | not established | 3 |
| Apple | 3.30–4.00 | Medium | 10.39 g | not established | 2 |
| Pineapple | 3.20–4.00 | Medium | 9.85 g | Low | not established |
| Peach | 3.30–4.05 | Low | 8.39 g | Low | 3 |
| Guava | 3.37–4.10 | Low | 8.92 g | not established | 3 |
| Clementine | 3.69–4.34 | Low | 9.18 g | not established | not established |
| Orange | 3.69–4.34 | Low | 9.35 g | High | 2 |
| Blackberry | 3.85–4.50 | Low | 4.88 g | not established | 2 |
| Sour cherry | 4.01–4.54 | Low | 8.49 g | not established | 2 |
| Sweet cherry | 4.01–4.54 | Low | 12.82 g | Low | not established |
| Pear | 3.50–4.60 | Low | 9.75 g | not established | 3 |
| Persimmon (Japanese) | 4.42–4.70 | Low | 12.53 g | not established | not established |
| Apricot | 3.30–4.80 | Low | 9.24 g | Low | 3 |
| Mango | 3.40–4.80 | Low | 13.66 g | not established | not established |
| Banana | 4.50–5.20 | Low | 12.23 g | not established | not established |
| Fig | 5.05–5.98 | Low | 16.26 g | not established | 3 |
| Honeydew melon | 6.00–6.67 | Low | 8.12 g | not established | not established |
| Blackcurrant | not established | not established | not established | High | 1 |
| Crabapple | not established | not established | not established | High | 1 |
| Cranberry | not established | not established | 4.27 g | High | 1 |
| Elderberry | not established | not established | not established | not established | 2 |
| Kiwi | not established | not established | 8.99 g | not established | not established |
| Redcurrant | not established | not established | 7.37 g | High | 1 |
No fruit in the register falls in that group.
pH from the FDA CFSAN approximate pH of foods tables. Sugars from USDA FoodData Central, SR Legacy release. Set groups from the University of Nebraska and Clemson extension listings. Where two sources disagreed on a range, the wider range is shown.
The table above is the readings. This is what they imply. Each fruit gets two answers rather than one, because they are two questions: whether it will set depends on pectin and acid together, and whether it is acid enough to can as it is depends only on where its range falls against 4.6. A fruit can be easy to set and still need acidifying before it goes in a jar.
18 of the 34 give an answer that is not established rather than a recommendation, because at least one of the two readings is missing from the sources. That is reported rather than filled in: a chart that answers for all thirty-four is guessing for eighteen of them.
Pectin not established
Its acid is measured at medium, but its pectin is not established, so whether it sets on its own is unproven. Test on a cold plate rather than trusting a chart.
Canning as it is Its whole measured range, 3.3–4, sits below 4.6.
Sets on its own
High pectin and acid enough. It gels without help, which is why it is also useful as a partner for fruits that do not.
Canning as it is Its whole measured range, 3.33–3.33, sits below 4.6.
Add acid and pectin
Short on both readings. Acid first, because pectin cannot gel without it, then pectin or a high-pectin partner.
Canning as it is Its range, 3.3–4.8, reaches past 4.6, so an individual fruit may fall either side of the line. Treat it as needing acidification.
Carries a set cooking apple (tart), gooseberry, grape, grapefruit, lemon, lime, plum, quince. High pectin and acid of their own, so they can carry this one.
Pectin not established
Its acid is measured at low, but its pectin is not established, so whether it sets on its own is unproven. Test on a cold plate rather than trusting a chart.
Canning as it is Its range, 4.5–5.2, reaches past 4.6, so an individual fruit may fall either side of the line. Treat it as needing acidification.
Pectin not established
Its acid is measured at low, but its pectin is not established, so whether it sets on its own is unproven. Test on a cold plate rather than trusting a chart.
Canning as it is Its whole measured range, 3.85–4.5, sits below 4.6.
Acid not established
Its pectin is recorded as high, but there is no measured pH, so no acid class is asserted and the set cannot be predicted from these two readings alone.
Canning as it is No measured pH in the sources, so nothing is asserted about canning it as it is.
Add pectin
Acid enough, pectin short. It needs added pectin or a high-pectin partner; boiling it down further concentrates sugar without creating the network that sets it.
Canning as it is Its whole measured range, 3.12–3.33, sits below 4.6.
Carries a set cooking apple (tart), gooseberry, grape, grapefruit, lemon, lime, plum, quince. High pectin and acid of their own, so they can carry this one.
Pectin not established
Its acid is measured at low, but its pectin is not established, so whether it sets on its own is unproven. Test on a cold plate rather than trusting a chart.
Canning as it is Its whole measured range, 4.01–4.54, sits below 4.6.
Add acid and pectin
Short on both readings. Acid first, because pectin cannot gel without it, then pectin or a high-pectin partner.
Canning as it is Its whole measured range, 4.01–4.54, sits below 4.6.
Carries a set cooking apple (tart), gooseberry, grape, grapefruit, lemon, lime, plum, quince. High pectin and acid of their own, so they can carry this one.
Pectin not established
Its acid is measured at low, but its pectin is not established, so whether it sets on its own is unproven. Test on a cold plate rather than trusting a chart.
Canning as it is Its whole measured range, 3.69–4.34, sits below 4.6.
Acid not established
Its pectin is recorded as high, but there is no measured pH, so no acid class is asserted and the set cannot be predicted from these two readings alone.
Canning as it is No measured pH in the sources, so nothing is asserted about canning it as it is.
Acid not established
Its pectin is recorded as high, but there is no measured pH, so no acid class is asserted and the set cannot be predicted from these two readings alone.
Canning as it is No measured pH in the sources, so nothing is asserted about canning it as it is.
Not established
Neither its pectin nor its acid is established in the sources. The cold-plate test is the only honest guide here.
Canning as it is No measured pH in the sources, so nothing is asserted about canning it as it is.
Pectin not established
Its acid is measured at low, but its pectin is not established, so whether it sets on its own is unproven. Test on a cold plate rather than trusting a chart.
Canning as it is Its whole measured range, 5.05–5.98, sits above 4.6, so acid has to be added before it is canned, not as a matter of flavour.
Sets on its own
High pectin and acid enough. It gels without help, which is why it is also useful as a partner for fruits that do not.
Canning as it is Its whole measured range, 2.8–3.1, sits below 4.6.
Sets on its own
High pectin and acid enough. It gels without help, which is why it is also useful as a partner for fruits that do not.
Canning as it is Its whole measured range, 2.8–3, sits below 4.6.
Sets on its own
High pectin and acid enough. It gels without help, which is why it is also useful as a partner for fruits that do not.
Canning as it is Its whole measured range, 3–3.75, sits below 4.6.
Pectin not established
Its acid is measured at low, but its pectin is not established, so whether it sets on its own is unproven. Test on a cold plate rather than trusting a chart.
Canning as it is Its whole measured range, 3.37–4.1, sits below 4.6.
Not established
Neither its pectin nor its acid is established in the sources. The cold-plate test is the only honest guide here.
Canning as it is No measured pH in the sources, so nothing is asserted about canning it as it is.
Sets on its own
High pectin and acid enough. It gels without help, which is why it is also useful as a partner for fruits that do not.
Canning as it is Its whole measured range, 2–2.6, sits below 4.6.
Sets on its own
High pectin and acid enough. It gels without help, which is why it is also useful as a partner for fruits that do not.
Canning as it is Its whole measured range, 2–2.8, sits below 4.6.
Pectin not established
Its acid is measured at low, but its pectin is not established, so whether it sets on its own is unproven. Test on a cold plate rather than trusting a chart.
Canning as it is Its range, 3.4–4.8, reaches past 4.6, so an individual fruit may fall either side of the line. Treat it as needing acidification.
Pectin not established
Its acid is measured at low, but its pectin is not established, so whether it sets on its own is unproven. Test on a cold plate rather than trusting a chart.
Canning as it is Its whole measured range, 6–6.67, sits above 4.6, so acid has to be added before it is canned, not as a matter of flavour.
Add acid
The pectin is there; the acid is short. Lemon juice is the correction, not more sugar, and not longer boiling.
Canning as it is Its whole measured range, 3.69–4.34, sits below 4.6.
Add acid and pectin
Short on both readings. Acid first, because pectin cannot gel without it, then pectin or a high-pectin partner.
Canning as it is Its whole measured range, 3.3–4.05, sits below 4.6.
Carries a set cooking apple (tart), gooseberry, grape, grapefruit, lemon, lime, plum, quince. High pectin and acid of their own, so they can carry this one.
Pectin not established
Its acid is measured at low, but its pectin is not established, so whether it sets on its own is unproven. Test on a cold plate rather than trusting a chart.
Canning as it is Its whole measured range, 3.5–4.6, sits below 4.6.
Pectin not established
Its acid is measured at low, but its pectin is not established, so whether it sets on its own is unproven. Test on a cold plate rather than trusting a chart.
Canning as it is Its range, 4.42–4.7, reaches past 4.6, so an individual fruit may fall either side of the line. Treat it as needing acidification.
Add pectin
Acid enough, pectin short. It needs added pectin or a high-pectin partner; boiling it down further concentrates sugar without creating the network that sets it.
Canning as it is Its whole measured range, 3.2–4, sits below 4.6.
Carries a set cooking apple (tart), gooseberry, grape, grapefruit, lemon, lime, plum, quince. High pectin and acid of their own, so they can carry this one.
Sets on its own
High pectin and acid enough. It gels without help, which is why it is also useful as a partner for fruits that do not.
Canning as it is Its whole measured range, 2.8–3.4, sits below 4.6.
Sets on its own
High pectin and acid enough. It gels without help, which is why it is also useful as a partner for fruits that do not.
Canning as it is Its whole measured range, 3.12–3.4, sits below 4.6.
Pectin not established
Its acid is measured at medium, but its pectin is not established, so whether it sets on its own is unproven. Test on a cold plate rather than trusting a chart.
Canning as it is Its whole measured range, 3.22–3.95, sits below 4.6.
Acid not established
Its pectin is recorded as high, but there is no measured pH, so no acid class is asserted and the set cannot be predicted from these two readings alone.
Canning as it is No measured pH in the sources, so nothing is asserted about canning it as it is.
Add pectin
Acid enough, pectin short. It needs added pectin or a high-pectin partner; boiling it down further concentrates sugar without creating the network that sets it.
Canning as it is Its whole measured range, 3.1–3.4, sits below 4.6.
Carries a set cooking apple (tart), gooseberry, grape, grapefruit, lemon, lime, plum, quince. High pectin and acid of their own, so they can carry this one.
Add pectin
Acid enough, pectin short. It needs added pectin or a high-pectin partner; boiling it down further concentrates sugar without creating the network that sets it.
Canning as it is Its whole measured range, 3–3.9, sits below 4.6.
Carries a set cooking apple (tart), gooseberry, grape, grapefruit, lemon, lime, plum, quince. High pectin and acid of their own, so they can carry this one.
Most of the low acid fruits in this register are tropical or stone fruits, and that is a useful shortcut for anything not listed. Taste is not a pH meter, but the ranking is stable: if a fruit tastes sharper than a ripe plum it is almost certainly under 4.0, and if it tastes flatter than a ripe peach it is almost certainly over. For the set, the test that settles it is a cold plate rather than a chart: a spoonful on a chilled saucer, pushed with a fingertip after a minute. If it wrinkles, it is set.
The two questions this table gets asked most are whether a mango is acidic and whether strawberries are, and both have the same shape of answer. Is mango acidic: not reliably, so treat it as a fruit that needs added acid. Are strawberries acidic: yes, but mildly, and their problem is pectin rather than acid.
A reading is not a quantity, and the next question is usually the quantity. For that, work out a batch takes any fruit in this register and a weight, and reports the sugar and water the fruit brings, the water that has to leave the pan, how many jars it fills and what share of the finished jar is fruit, from these figures, and blank where these figures are blank.
On these measurements the flattest are fig (pH 5.05 to 5.98), banana, honeydew melon and Japanese persimmon. All four sit above the pH 4.6 line, which means acid is not doing any preserving work in them and they need either added acid or a pressure canner.
Usually not. The measured range is pH 3.40 to 4.80, and a ripe mango sits at the top of it. Its pectin is not established in these sources either, so mango jam is normally made with both added acid and added pectin, or with a high-pectin partner fruit.
Quince, crabapple, cranberry, redcurrant, blackcurrant, gooseberry, grape, plum, tart cooking apple and the citrus fruits. Thirteen of the thirty-four here carry a high pectin class, and any one of them added to a weak setter does the same job as a packet of pectin.
Sugar is one of the three conditions, but it cannot substitute for a missing one. A set needs pectin, acid and sugar together; if the pectin is low, boiling in more sugar concentrates the syrup without building the gel, and the result is thick rather than set.
That the sources used carry no measured figure for that fruit and field. It is not the same as zero, and it is not an estimate. Six fruits here have no published pH and fourteen have no pectin class, so those cells say so rather than filling the gap with a plausible number.
Like a Strawberry Milk · https://www.likeastrawberrymilk.com/2015/06/sugar-acid-and-pectin-content-of-fruits/
