Dry Substance in Syrups: The Hidden Water in Your Mix
Table of contents
Weigh 100 g of glucose syrup into a mix and you have added about 80 g of sugar and 20 g of water. Most recipe sheets record the first number and forget the second. That forgotten water is why a base reading 38 percent solids on paper serves like one at 36.
Dry Substance, Defined
Dry substance, also called dry matter or by its Italian name sostanza secca, is the fraction of a product left once all the water is driven off. A sugar at 80 percent dry substance is 80 percent solids and 20 percent water by weight, and both halves have to appear somewhere in the balance.
Crystalline sugars make this easy by being almost pure. Sucrose is 100 percent dry substance. Dextrose monohydrate carries one molecule of water of crystallisation, so at 198 g/mol against 180 for the anhydrous form it delivers about 91 percent sugar solids and nothing anyone needs to think about further.
Syrups are the problem, and the law sets only floors. EU Directive 2001/111/EC requires glucose syrup to carry at least 70 percent dry matter, dried glucose syrup at least 93 percent, and sugar solutions and invert sugar syrups at least 62 percent. Those are minima, not typical values, which is exactly why the specification sheet rather than the category name has to drive the number you enter.
The Table Every Lab Needs
| Product | Typical dry substance | Water per 100 g |
|---|---|---|
| Sucrose, dextrose anhydrous | 100% | 0 g |
| Dextrose monohydrate | about 91% | about 9 g |
| Maltodextrin | about 95% | about 5 g |
| Glucose syrup DE 38 to 60 | 78 to 84% | 16 to 22 g |
| Invert sugar syrup | 70 to 78% | 22 to 30 g |
| Honey | about 83% | about 17 g |
| Maple syrup | about 68% | about 32 g |
| Sweetened condensed milk | about 73% | about 27 g |
| Unsweetened fruit purée | 8 to 14% | 86 to 92 g |
The honey and maple figures come from USDA FoodData Central, which records honey at roughly 17 percent water and maple syrup at roughly 32 percent. Maple carries a legal floor of its own: the grading standards in both the United States and Canada require a minimum density of 66.0 degrees Brix, so a genuine syrup cannot be much wetter than the table says.
Quick reference. Enter every wet sweetener twice: once as its solids, once as the water it brings. A syrup at 80 percent dry substance used at 90 g in a 1000 g base contributes 72 g of sugar solids and 18 g of water, and that water counts against the milk.
What the Error Costs You
Take a 1000 g milk base with 90 g of DE 38 glucose syrup at 80 percent dry substance.
Recorded as 90 g of sugar, the sheet reports 90 g of solids from that line. In reality it delivers 72 g. The recipe is 18 g of solids poorer than it claims, which on a 1000 g batch is 1.8 percentage points of total solids. A base that was aimed at the middle of the 36 to 42 percent band lands near the bottom of it, and the symptoms are the familiar ones: fast melt, thin body, more perceptible ice.
The 18 g of water compounds the error from the other side. It is not free water in a sheet that never recorded it, so the milk quantity was never reduced to make room for it. The mix is wetter than intended by both accounts at once.
Sweetened condensed milk is where this gets expensive, because it hides two things: about 27 g of water per 100 g and a substantial load of both sugar and MSNF in the remainder. Recording it as a sugar loses the milk solids; recording it as a milk loses the sugar. It has to be split three ways.
Two Conventions, One Common Mistake
Coefficient tables circulate in both forms, and mixing them is the second classic error.
A coefficient quoted as sold already accounts for the water. The PAC 67 usually given for a DE 38 glucose syrup is an as sold figure: it describes 100 g of the product in the pail.
A coefficient quoted on dry matter describes only the solids, and needs scaling before use. The conversion runs in one direction and is worth writing on the wall of the lab:
PAC as sold = PAC on dry matter × dry substance fraction
For the same syrup, a dry matter figure of 84 becomes 84 × 0.80 = 67 as sold. Use the dry matter number without scaling and you overstate the anti freezing contribution by a quarter, which shows up as a base that serves harder than the sheet promised. The same conversion applies to POD.
If a table does not say which convention it uses, test it against a known product. Sucrose is 100 in both conventions because it has no water; glucose syrup is the one that betrays which column you are reading.
Measuring It Yourself
The reference method is gravimetric. Weigh a sample, dry it to constant weight in an oven, weigh again, and the ratio is the dry substance. It is accurate, it is slow, and almost no gelato lab does it.
The working method is refractive. A refractometer reads degrees Brix, defined as grams of sucrose per 100 g of solution, and for pure sugar syrups Brix and dry substance are effectively the same number. This is the fastest way to check a fruit purée, and it is the basis of the Brix versus total solids discussion in sorbetto work.
Two cautions apply. First, the scale is calibrated for sucrose, and glucose syrups bend light slightly differently, so a Brix reading on a syrup is close but not exact and the supplier specification wins where they disagree. Second, a refractometer sees dissolved solids only. Fibre, pulp and suspended matter in a purée go uncounted, so a purée at 11 °Bx carries a little more total dry substance than the Brix meter shows.
Building It Into the Sheet
Give every wet ingredient its own dry substance column, and let the sheet compute solids and water from it rather than typing them by hand. Then the number to audit is one per ingredient rather than three.
Re balance the water line whenever a syrup changes. Swapping a DE 38 syrup for a DE 60 one at the same weight looks harmless and usually moves both PAC and dry substance, and the total solids calculator will show the drift immediately if the dry substance figure was entered honestly.
Finally, re read the specification sheet at every delivery. Dry substance is a contractual property that suppliers do change, and a two point shift on a syrup used at nine percent of the mix is enough to move the batch by a fifth of a point of solids. That is small, until it is the difference between a base that scoops and one that does not.
Related Concepts
- Total solids in gelato for the target band this feeds
- Brix vs total solids for the sorbetto version of the question
- Glucose syrup for grade by grade dry matter and PAC
- Maltodextrin vs glucose syrup for choosing between a dry and a wet solids source
- Refractometer in the gelato lab for how to take the reading
- Total solids calculator for running the numbers
