What does 65 percent soluble solids mean, and does my jam meet it?

Updated October 2026

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What the number measures The figures in each standard How the regulation says to measure it Checking your own batch When the reading falls short Run your reading through the check References

Soluble solids are everything dissolved in the jam's liquid, mostly sugar with some fruit acids and other compounds, expressed as a percentage of the jam's weight. Federal standards require at least 65 percent for jam, preserves and jelly, and at least 43 percent for fruit butter [1][2][3]. The official method is a refractometer reading, with no correction for the insoluble bits of fruit [1]. If your product reads below the line, it can still be a good food, but it cannot be sold under the standard name. This page explains what the number measures, how the rule says to read it, and how to check your own batches before they go on a shelf.

What the number measures

Pick up a spoonful of strawberry jam and think of it as two parts: the solid fruit tissue you could filter out, and the syrup around it. The syrup is water carrying dissolved sugar, fruit sugars, acids, pectin and minerals. "Soluble solids" is the weight of everything dissolved in that liquid, as a share of the total. A reading of 65 means that, by the instrument's scale, 65 percent of the sample is dissolved solids and the rest is mostly water.

Refractometers measure how strongly a liquid bends light, which rises with dissolved sugar. They are calibrated in degrees Brix, a scale built on sucrose solutions, so 65 °Brix reads as 65 percent soluble solids. Penn State's commercial primer uses the two terms together: jams and jellies must reach 65 percent soluble solids, which it also writes as 65 percent Brix [4]. Because jam's dissolved solids are mostly sugars, the Brix reading is a close and accepted stand-in.

The 65 percent line ties the legal names to the traditional high-sugar product: one that sets with ordinary pectin and keeps well in the pantry. The science of why sugar does that work, and why cutting it changes the set, is on what makes jam set.

The figures in each standard

Product	Minimum soluble solids	Where it is set
Jam and preserves	65 percent: "not less than 65 percent"	21 CFR 150.160(d)(5) [1]
Fruit jelly	65 percent: "The soluble-solids content of the finished jelly is not less than 65 percent"	21 CFR 150.140 [2]
Fruit butter	43 percent: "not less than 43 percent"	21 CFR 150.110(d)(3) [3]
Nonstandardized fruit jelly (such as huckleberry)	65 percent	FDA CPG 550.475 [5]
Nonfruit jelly (pepper, wine, herb)	65 percent	FDA CPG 550.475 [5]
Marmalade, conserve, fruit spread	No federal figure	No standard of identity [4]

USDA's voluntary grade standard for preserves sets the same floor: product must have a solids content of at least 65 degrees Brix to be graded at all [6]. Grades are covered on USDA grades for jelly and preserves.

The old saccharin-sweetened jam standard (21 CFR 150.161) had no soluble-solids floor at all; it set fruit at a minimum of 55 percent of the finished food instead [7]. That former standard no longer appears in the current Part 150 [8], and a jam made with a sugar substitute is now sold under a descriptive name.

How the regulation says to measure it

Each standard names a refractometer method from the Official Methods of Analysis of the Association of Official Analytical Chemists, 13th edition (1980), and the section number differs by product. The jam and preserves standard cites section 22.024, the refractometer method for soluble solids, "except that no correction is made for water-insoluble solids" [1]. The jelly standard cites section 31.011, also a refractometer method [2]. The fruit butter standard uses section 22.024, as the jam standard does [3].

Two points come out of that text:

The test is a refractometer reading. A thermometer, a sheet test on a spoon or a hydrometer tells you when a batch is likely done; none of them is the legal measure. They are compared on how to tell when jam is done.
You read the jam as it is. The "no correction" clause means you do not adjust the number for fruit pulp or seeds. You read the liquid portion of the product and that reading stands.

You do not need a copy of the 1980 AOAC volume to run a sound check. If your state agency or a buyer asks how you measured, "refractometer reading per AOAC 22.024, as referenced in 21 CFR 150.160" is the answer for jam and preserves, and "per AOAC 31.011, as referenced in 21 CFR 150.140" for jelly.

Checking your own batch

The instrument, its calibration and its quirks have their own page, using a refractometer. For the legal check, the sequence is:

Use a refractometer whose scale reaches comfortably past 65 °Brix. Many units sold for wine, beer or juice stop well short of jam's range. You need a high-range model, ideally with automatic temperature compensation.
Zero it with distilled water at room temperature before each session.
Take a sample from the pan near the end of cooking, and cool it before reading. Penn State's directions are to cool hot samples in a capped container before measuring [4]. Capping keeps steam from carrying off water and pushing the reading falsely high.
Spread a thin layer of the liquid portion on the prism, avoiding large fruit pieces and seeds, and read the scale.
Decide in the pan. Penn State's process is to turn off the heat and fill once the batch reaches 65 percent [4]. If it reads 63, cook a little longer and test again. Once jam is in sealed jars you cannot adjust it.
Record the reading on the batch sheet with the date, the batch number and the instrument. That record is your evidence if anyone asks whether a lot met the standard. The batch log template has a column for it.
Read a finished jar now and then, at room temperature, from a sample of the cooled, set product. It confirms that what you measured in the pan matches what the customer gets.

Overshooting has its own cost. Penn State warns that overconcentration can produce a gummy texture or crystals after cooling [4]. Aim to land at 65 to a little over, not at 70.

When the reading falls short

What you see	What it means	What to do
A full-sugar pectin recipe reads a point or two short in the pan	Not cooked far enough yet	Keep cooking briefly and retest before filling
A finished, sealed batch reads below 65	The batch is not standard jam	Sell it under a descriptive name, such as "fruit spread," if your state allows it; otherwise keep it for home use. You cannot relabel it "jam"
A low- or no-sugar pectin recipe reads well below 65	Working as designed; these products are not meant to reach 65	Label it as a fruit spread [4]; check whether your cottage law allows it (what cottage food laws often exclude)
Fruit butter reads below 43	Below the 43 percent floor for "butter" [3]	Cook down further before filling, or use another name
Readings vary widely between batches of one recipe	Fruit ripeness and water content are changing	Standardize by weight and target reading; see making every batch the same

A reading below 65 is also a keeping-quality signal. The National Center for Home Food Preservation notes that reduced-sugar products may lose quality sooner in storage and generally have a shorter refrigerated life once opened [9]. Those spreads depend on a tested recipe and processing, not on sugar, for their safety on the shelf; the methods that can be canned are on how to make low-sugar jam that sets and keeps.

Run your reading through the check

If you have a reading and want a quick answer, the soluble solids check takes the product type and the number and tells you which name it supports. If you have not bought a refractometer yet, start with using a refractometer, which covers range, temperature compensation and calibration.

References

Legal Information Institute, Cornell Law School, 21 CFR 150.160, Fruit preserves and jams, paragraph (d)(5) (current text), accessed October 2026. https://www.law.cornell.edu/cfr/text/21/150.160
Legal Information Institute, Cornell Law School, 21 CFR 150.140, Fruit jelly (current text), accessed October 2026. https://www.law.cornell.edu/cfr/text/21/150.140
Legal Information Institute, Cornell Law School, 21 CFR 150.110, Fruit butter, paragraph (d)(3) (current text), accessed October 2026. https://www.law.cornell.edu/cfr/text/21/150.110
Penn State Extension (L. LaBorde), Food for Profit: Commercial Production of Jams, Jellies, and Fruit Butters, updated May 24, 2024. https://extension.psu.edu/food-for-profit-commercial-production-of-jams-jellies-and-fruit-butters
U.S. Food and Drug Administration, CPG Sec. 550.475 Jellies, Nonstandardized, revised May 2005, updated November 29, 2005. https://www.fda.gov/regulatory-information/search-fda-guidance-documents/cpg-sec-550475-jellies-nonstandardized
USDA Agricultural Marketing Service, United States Standards for Grades of Fruit Preserves (Jams), effective January 4, 1980. https://www.ams.usda.gov/sites/default/files/media/Canned_Fruit_Preserves_(Jams)_Standard[1].pdf
U.S. Government Publishing Office, 21 CFR 150.161, Artificially sweetened fruit preserves and jams, Code of Federal Regulations, April 1, 1996 edition (historical text). https://www.govinfo.gov/content/pkg/CFR-1996-title21-vol2/html/CFR-1996-title21-vol2-sec150-161.htm
Legal Information Institute, Cornell Law School, 21 CFR Part 150, Subpart B (sections 150.110 to 150.160), accessed October 2026. https://www.law.cornell.edu/cfr/text/21/part-150/subpart-B
National Center for Home Food Preservation, Storing Home Canned Jams and Jellies, October 2005. https://nchfp.uga.edu/how/make-jam-jelly/jams-jellies-general-information/storing-home-canned-jams-and-jellies/