Residues, steam and “incidental contact”: whose condition is it?

A processing aid is a technical effect with a definition

21 CFR 170.3(o) lists the physical or technical functional effects for which direct human food ingredients may be added to foods, adopted from a September 1972 National Academy of Sciences/National Research Council survey. Paragraph (o)(24) defines processing aids as “substances used as manufacturing aids to enhance the appeal or utility of a food or food component, including clarifying agents, clouding agents, catalysts, flocculents, filter aids, and crystallization inhibitors, etc.” Paragraph (o)(27) defines solvents and vehicles as “substances used to extract or dissolve another substance.” The affirmation entries use these terms as conditions of use: § 184.1613 names potassium bicarbonate as a formulation aid, nutrient supplement, pH control agent and processing aid, and § 184.1666 names propylene glycol as, among twelve effects, a processing aid and a solvent and vehicle.

An effect describes what a use does in a particular food. It is not an attribute of a material, a supplier cannot confer it by shipping one, and the same substance can sit inside one effect and outside another. The question for a purchasing record is which effect the facility relies on, under which section, and who made that call. The first guide in this collection deals with the listing and its specification; this brief looks at three places where federal text sets conditions on a processing or utility use rather than on an ingredient.

Hexane: the limit is written on the food

21 CFR 173.270 opens: “Hexane may be present in the following foods under the conditions specified.” Paragraph (a) allows it in spice oleoresins “as a residue from the extraction of spice, at a level not to exceed 25 parts per million.” Paragraph (b) allows it in hops extract “as a residue from the extraction of hops, at a level not to exceed 2.2 percent by weight,” provided that the hops extract is added to the wort before or during cooking in the manufacture of beer, and that its label specifies the presence of the hexane and provides for use of the extract only in that way.

Read what the section limits and what it does not. Both numbers are residues in a named food—one in parts per million, one in percent by weight—and both attach to the extract, not to the solvent that made it. The section names two foods and no others, states no assay, grade, composition or impurity limit for the hexane, and says nothing about any other use of it. A buyer of the solvent learns from it which residue a finished extract is measured against. The residue measurement, its method and the owner of the result all sit with the extractor.

“Hexane” is not one composition

The aggregated public record for hexane shows why the solvent side needs an identity of its own. A Hazardous Substances Data Bank entry describes the technical grade as “a mixture of approx 50% n-hexane and 50% isohexane and cyclohexane,” with no basis stated for either figure. The record’s registry numbers include 110-54-3 and 92112-69-1, and its depositor-supplied synonyms run from “n-Hexane” to “Hexanes.” Several materials share one word.

The Joint FAO/WHO Expert Committee on Food Additives made the point directly at its sixty-fifth meeting in 2005: “As used in the food industry, ‘hexane’ is a mixture of hydrocarbons,” whose composition “will depend on the region of production, the source of the raw material and the site of production,” so that the committee concluded “the present articles of commerce differ from those previously evaluated by JECFA,” and it recommended a re-evaluation. That statement is two decades old and is quoted as dated evidence, not as a current position. The stable part is the purchasing consequence: a solvent specification has to say which material is meant—normal hexane or a hexanes mixture, with an assay, its basis and a method—and a grade designation alone does not answer that. What a designation such as ACS certifies is covered in the laboratory and pharmaceutical research collection. Nothing here states that any Alliance solvent is suitable for, or permitted in, any extraction.

Boiler water: the condition is on the steam

21 CFR 173.310 sets the conditions under which boiler water additives may be used in preparing steam that will contact food. Paragraph (a) is a quantity condition on two things at once: “The amount of additive is not in excess of that required for its functional purpose, and the amount of steam in contact with food does not exceed that required to produce the intended effect in or on the food.” Paragraph (b) requires the compounds to be prepared from the substances listed in paragraphs (c) and (d), subject to any limitations stated there. Sodium hydroxide appears in the paragraph (c) list with no limitation beside it; other entries carry limits in parts per million in boiler feedwater or in steam, and several paragraph (d) entries exclude steam that contacts milk and milk products. The acetic acid affirmation at § 184.1005 cross-refers here, naming use “as a boiler water additive complying with § 173.310.”

Paragraph (e) is the part a purchasing team tends to skip. The label or labeling of the additive must bear “the common or chemical name or names of the additive or additives” and “adequate directions for use to assure compliance with all the provisions of this section.” The section regulates an additive as used—labelled, with directions—in a boiler producing steam for a stated contact. A listed substance delivered as a commodity chemical is not by that fact a labelled boiler water additive, and the treatment programme, its feedwater and steam limits, and the contact the steam has with food are for the facility and its water-treatment provider to own. This brief sets no dose, feed rate or treatment programme.

“Incidental food contact” as federal text uses it

The phrase has a home in 21 CFR 178.3570, and the home is lubricants. The section provides for lubricants with incidental food contact on machinery used for producing, manufacturing, packing, processing, preparing, treating, packaging, transporting or holding food, prepared from GRAS substances, from substances used under a prior sanction or approval, or from the substances in its own table with their limitations. Paragraph (b) names the uses: “as a protective antirust film, as a release agent on gaskets or seals of tank closures, and as a lubricant for machine parts and equipment in locations in which there is exposure of the lubricated part to food.” The amount used is the minimum required for the technical effect on the equipment, and the addition to food of any constituent identified in the section must not exceed its limitation—for several table entries, “Addition to food not to exceed 10 parts per million.”

Two things follow. The federal condition is a composition, a use and a limit on what reaches the food, written for a lubricant in a named set of uses; paragraph (b) does not name heat transfer among them, and none of the federal text read for this brief sets an equivalent condition for a heat-transfer fluid. And the condition attaches to a finished lubricant used in a particular way, not to a material that might be one of its components.

HT1 is a registration of a named formulation

The incidental-contact category most buyers of heat-transfer fluid meet is a private one. NSF’s quick reference guide to its nonfood compound categories lists HT1 as “Heat transfer fluids - Incidental contact” and HT2 as “Heat transfer fluids - no food contact,” alongside H1, “General – incidental contact,” for lubricants. It lists HTX1, “Ingredients for use in HT1 heat transfer fluids,” as a separate category, with HTX2 for HT2 fluids. Because the guide lists a component category and a finished-fluid category separately, the registration of a component and the registration of a finished fluid have to be checked separately.

NSF’s White Book listing directory shows what a registration attaches to: a company, a product name, a registration number and one or more category codes, with the product name linked to a registration letter. On September 14, 2026 the directory stated it was current as of that morning and asked readers to confirm any listing with NSF. Registration status is therefore a lookup the buyer performs—by exact product name and registration number, at the date of purchase, keeping the letter—and it covers the named product only. A fluid with the same glycol percentage, or the same base glycol with a different inhibitor package, is not covered by another product’s registration. Why an inhibited glycol is a formulation rather than a chemical, and what an inhibitor claim does and does not establish, are covered in this library’s HVAC and geothermal collection under “Inhibited and uninhibited glycol are different purchases” and “A corrosion-inhibitor claim is a claim about evidence.” Nothing in this library states or implies that any Alliance product holds an NSF registration or any incidental-contact status, and none should be inferred from a product name, a collection or a percentage.

What this brief did not read, and what can change

The Food Chemicals Codex in any edition and NSF’s registration guidelines were not read: the Codex publisher’s page and NSF’s nonfood compounds pages on nsf.org both returned 403 to an unauthenticated request on September 14, 2026, and only the category guide and listing directory on info.nsf.org were readable. Neither document is paraphrased here and no limit is reproduced from either. Where a specification invokes one, obtain the edition it invokes and cite the clauses by number.

The regulatory position also moves. FDA’s GRAS overview page records that on August 10, 2026 the agency proposed a rule to enhance oversight of uses of substances added to human and animal food that are claimed to be GRAS, under docket FDA-2025-N-3262. The proposal was not read for this brief and is not final; it is noted so that anyone relying on a GRAS position checks its status at the date of use. This brief performed no original testing, conducts no hazard analysis, determines the regulatory status of no use, and sets no use level, dose, feed rate or cleaning procedure. Nothing in it states that any Alliance product is suitable, approved or recommended for use in food, on food-contact equipment or in any other application. Independent specialist review of this collection is pending.

• Which technical effect and which section of 21 CFR does this processing use rely on, and who determined that?
• Where a residue limit applies, which analyte does the method measure, and who owns the result?
• For steam that contacts food, which labelled additive is used, and who owns the boiler water programme?
• For an incidental-contact claim, which exact product name, registration number and category code were looked up, on what date, and where is the letter kept?

Requirement → evidence → decision boundary

An editorial checklist for your review—not a table of product specifications.

Revision record

1.0 · September 14, 2026 — Source-based editorial edition. No original testing or product qualification is claimed.

For food and beverage manufacturers, their preventive controls qualified individuals and purchasing teams specifying ingredients, processing aids and utility chemistry. This collection does not determine the regulatory status of any use, perform a hazard analysis, approve or verify a supplier, set a use level, dose or feed rate, write a cleaning procedure, or establish that any material is fit for use in food or on food-contact equipment.